                                                                                VIEWSEIS provides a complete set of functions for seismic refraction            analysis based on the Generalized Reciprocal Method.                                                                                                            1.1  Program Operation:                                                                                                                                         Menu Selection:                                                                 Menus and functions within VIEWSEIS can be selected by placing the mouse        cursor on the item, and pressing a mouse button. In addition, menu names        listed on the top line of the screen can be selected by typing the first        letter (capitalized) of the menu name.                                                                                                                          VIEWSEIS Files:                                                                 All arrival picks, interpretation and VIEWSEIS parameters can be saved          in files with the extension '.vs'.  File save and load functions are            accessed from the File Menu.  Each VIEWSEIS file contains all the               information associated with a single seismic line.                                                                                                              1.2  GRM Interpretation using VIEWSEIS:                                                                                                                         Shot Data Preparation:                                                          Arrival time information within VIEWSEIS is grouped by shot number. Shots       can be either forward, reverse or mid, depending on the position of the         shot relative to the line direction.  The user must keep track of shot          and geophone positions, shot direction and geophone spacing during field        recording.                                                                                                                                                      Arrival Time Picking:                                                           First break arrival times are loaded into VIEWSEIS through the Shot Data        Menu, and can be entered via three methods:                                             1. Picked as first breaks from the digital trace files                          2. Loaded from Pick files or ASCII x,t files                                    3. Manually entered by typing the arrival times                                                                                                         Layer Assignment:                                                               The first interpretation task involves assigning each arrival to a sub-         surface layer. This is performed in the Layer Menu.                                                                                                             Phantoming:                                                                     The Phantoming process involves time shifting the arrival times from            various overlapping shots to form a complete set of forward and reverse         arrival times along the line. Arrivals from each layer must be phantomed,       or assigned to layer 0 to be excluded from processing.                                                                                                          GRM Analysis:                                                                   Once phantoming is complete, GRM analysis begins with velocity analysis         and the selection of the optimum XY value. This is completed for each           layer, and performed in the GRM Menu.                                                                                                                           Output:                                                                         Paper copies of all the processing steps can be created at any time,            however extensive plotting is usually not needed, as all analysis is            performed on-screen. The output functions are accessed from the Output -         Plot Menu.                                                                                                                                                     1.3  Menu Map                                                                                                                                                   The following is a list of all VIEWSEIS Menus, indented to show sub-menus       accessed from the                                                               Main Menu.                                                                                                                                                      File Menu:                                                                              - File Selection Menu                                                           - Configuration Menu                                                    Data Menu:                                                                              - Shot Control Menu                                                                     - Shot Edit Menu                                                                         - Trace Load Menu                                                                       - Trace Display Menu                                                                    - Trace Pick Menu                              - Ground Elevation Menu                                                         - Header Menu                                                                   - Control Menu                                                          Layer Menu:                                                                             - Model Menu                                                                    - Zoom Menu                                                                             - Pan Menu                                                              - View Menu                                                             GRM Menu:                                                                               - Layer Selection Menu                                                          - XY Analysis Menu                                                                      - Zoom Menu                                                                              - Pan Menu                                                     - Control Menu                                                                  - Segment Menu                                                                          - Velocity Input Menu                                                           - XY Input Menu                                                         - Zoom Menu                                                                             - Pan Menu                                                              - View Menu                                                             Output Menu:                                                                            - Plot Menu                                                                             - Plot File Control Menu                                                - Export Menu                                                                   - Borehole Menu                                                         Zoom Menu:                                                                              - Pan Menu                                                              View Menu:                                                                                                                                                                                                                                      The Auto Pick function can be used to pick the first break arrival times.       The procedure requires, however, that the data is of relatively good            quality. The user has control of the sensitivity of the pick procedure.                                                                                         Once the Auto Pick function is selected, the user will be prompted for          two control values; the trace amplitude value and the search back               amplitude.  The auto pick function starts at the beginning of each trace,       searching for a measurement which exceeds the trace amplitude value. Once       found, it searches back up the trace, looking for a measurement which is        less than the search back amplitude. The arrival is placed at the point         the search back value is found.                                                                                                                                 In general, set the search amplitude to a value somewhat less than the          maximum amplitude of a typical first break. Set the search back amplitude       to a much smaller value.                                                                                                                                                                                                                        Sub-surface layer interfaces identified from boreholes can be entered in        this menu. This feature provides a quick procedure for plotting layer           interfaces on the seismic cross section.                                                                                                                        3.1  Menu Items:                                                                                                                                                Label: The name of the borehole (text or numbers)                                                                                                               Line Pos: The line position of the borehole.                                                                                                                    Surface: The elevation of the top of the borehole. This need not be equal       to the ground elevation.                                                                                                                                        Layer: The elevation at which the layer interface was identified in the         borehole.                                                                                                                                                                                                                                                                                                                       Program hardware and software settings are set within the Configuration         Menu.  Program configuration consists of selecting the graphics adaptor         and setting the program directory.                                                                                                                              VIEWSEIS initially attempts to automatically configure itself, but if           this is unsuccessful, the program will immediately enter the                    Configuration Menu.                                                                                                                                             4.1  Menu Items:                                                                                                                                                4.1.1  Video Configuration:                                                                                                                                     Selected Video Option: The program can either automatically detect the          graphics adaptor, or it can be set manually with this option. To change         the graphics adaptor, first click on Selected Video Option, then use the        left and right arrow keys to select the appropriate hardware.                                                                                                   Number of Screen Colours: This option can be used to set black and white        (2 colour) mode for laptop computers.                                                                                                                           Base font number: Font number 1 is largest, and 3 is smallest. Some             graphics cards only allow one font, in which case this option is ignored.                                                                                       Automatic Identification: This is the adaptor identified by the program,        and used if the "Selected video option" is set to "Automatic                    Identification". In most cases should indicate the correct hardware.                                                                                            4.1.2  Program Directory Configuration:                                                                                                                         The program needs to know the disk and directory in which the program           files are located.  VIEWSEIS will automatically search the DOS path for         these files if they are not found. These parameters need only be set if         the DOS path does not include the VIEWSEIS directory, and the program is        not started from the VIEWSEIS directory.  To set these options, first           select with the mouse, then enter the correct directory.                                                                                                        VIEWSEIS and Help file Directory: The viewseis.exe, vshelp.hlp and              vsindex.hlp directory.                                                                                                                                          Plot.exe Directory: The plot.exe, view.exe, install.exe and install.dlb         directory (usually the same as above).                                                                                                                          4.1.3  Output Device Configuration:                                                                                                                             The currently installed printer device is displayed in this portion of          the screen. Click on this option to select a printer type, output port,         page size and rotation.                                                                                                                                                                                                                         The Control Menu allows the user to set the various GRM calculation             parameters. Most important, the Control Menu allows the user to select          how the velocity and depth calculations are performed.                                                                                                          Ideally, the GRM method should be used on all layers, however this              requires that enough refracted arrivals must be recorded to accurately          assign and phantom values along the entire seismic line. If there are           insufficient arrivals to fully phantom either layer 2 or 3, the time            intercept method can be used to determine the velocity and depth of             layers 2 and/or 3.                                                                                                                                              5.1  Menu Items:                                                                                                                                                5.1.1  XY Control Parameters:                                                                                                                                   Global XY Start: This is the first XY distance used in XY and Time-depth        plots.                                                                                                                                                          XY Increment: The increment between XY calculation lines.                                                                                                       XY Stop: The last XY calculation value.                                                                                                                         Optimum XY: The user selected optimum XY value, used for all subsequent         GRM calculations.                                                                                                                                               5.1.2  Velocity and Depth Migration Parameters:                                                                                                                 Vel. Smoothing: Changes in the layer velocities can be smoothed to              suppress sharp breaks in the depth section.  Smoothing is performed using       an n-point weighted moving average, where the value of n is set in this         column. Enter 0 for no smoothing, and values up to 10 to produce                reasonable results.                                                                                                                                             Arc Angle: The Arc swing angle (in degrees) for presenting the layer            interface on the depth section.  If an angle of 0 is entered, straight          lines will be used to represent layer boundaries on the depth section.                                                                                          Depth Migration: The method of determining the layer velocity and depth         is selected in the Depth Migration column. Each layer can use a different       method. The Layer 1 selection only refers to the method of determining          the layer velocity. The following methods are available.                                                                                                                Intercept Method: The Intercept method can be used only for layers              one, two or three. If the intercept method is selected, it is not               necessary to phantom the layer arrivals. This method generally gives            the poorest results.                                                                                                                                            Average Method of Depth Migration:                                              Advantages: This method does not require any upper layer model, as              it calculates the average velocity above the refracting layer during            migration.                                                                                                                                                      Disadvantages: The method cannot be used with a zero optimum XY                 value, and it is very sensitive to changes in the XY distance.                                                                                                  Approximate Velocity Method of Depth Migration:                                 Advantages: This method is not highly sensitive to the XY value, and            the XY distance can be zero. When optimum XY=0, this method is                  identical to Delay Time methods.                                                                                                                                Disadvantages: This method requires complete calculation of the                 upper layer velocities and all upper layer thicknesses.                                                                                                                                                                                 The Data Menu provides access to the various data input menus.                                                                                                  6.1  Sub-Menus:                                                                                                                                                 Shot Control Menu: For loading arrival time data, including first break         picking.                                                                                                                                                        Ground Elevation Menu: To enter ground surface information.                                                                                                     Header Menu: To enter global seismic line information. In addition, the         distance units (feet or metres) can be set in this menu.                                                                                                        Control Menu: To enter global GRM parameters such as XY distance, and the       method of velocity analysis and depth migration.                                                                                                                                                                                                                                                                                This menu provides functions for loading and saving files, and setting          the program configuration.                                                                                                                                      7.1  Sub-Menus:                                                                                                                                                 Program Configuration: Used to set the graphics and program directory                                                                                           7.2  Menu Items:                                                                                                                                                7.2.1  DOS/File Options:                                                                                                                                        Create a new VIEWSEIS file: This option clears the existing                     interpretation from memory.                                                                                                                                     Load a new interpretation file: This option directs the program to the          File Selection Menu, from which the user can load GRM line interpretation       results. VIEWSEIS stores interpretation results from each seismic line          in files which have the extension '*.vs'.                                                                                                                       Save the data and interpretation in a VIEWSEIS file: All the                    interpretation parameters are saved in a file (with extension *.vs) when        this option is selected.                                                                                                                                        DOS Shell: When this option is selected, the program loads a DOS shell          system. The current program and data are swapped to LIM 4.0 Expanded            memory, if available, or to disk if not.  This allows the user to copy          files and perform other DOS tasks all while VIEWSEIS remains in                 operation.                                                                                                                                                      CAUTION: It is recommended that VIEWSEIS interpretation and editing             changes should be saved prior to loading the shell.                             IMPORTANT NOTE: To exit the shell and return to VIEWSEIS, type EXIT at          the DOS command prompt.                                                                                                                                                                                                                         The File Selection Menu allows the user to select DOS files.  The menu          is called when the user must select either a VIEWSEIS '.vs'                     interpretation file, or trace data files.                                                                                                                       8.1  Menu Items:                                                                                                                                                Changing directories:                                                           To change to a different sub-directory, simply point with the mouse at          the desired directory, and press a mouse button.  Select the '..' name          to change to the directory one level higher than the current directory.         Select the '.' name to re-read the current directory.                                                                                                           Changing the disk drive, path or file mask:                                     The current disk, path and file mask are displayed on the line which            separates the directory and file names, and starts with the name "Disk          Files:".  To change to a different disk, directory or file mask, point          at this line, and press a mouse button to begin editing. The default file       mask depends on the calling function. For example, the default mask is          '*.vs' when called to load a VIEWSEIS file, and '*.pik' when called to          load an arrival pick file.                                                                                                                                      Loading a file:                                                                 To load a file, point to the file name with the mouse, and press a mouse        button.                                                                                                                                                                                                                                         The GRM Menu provides access to the various GRM interpretation functions.       Before accessing the GRM functions, Layer Assignment and Phantoming must        be completed. Note that the Control Menu is used to set the GRM specific        parameters for each layer. Upon entry into this menu, arrival averaging         and interpolation are automatically performed to create a complete set          of forward and reverse arrival times.                                                                                                                           Arrival Averaging: This automatic procedure involves averaging all              arrivals with the same line position and layer number, improving the            arrival time pick for that location. For example, if a zero offset and          long offset shot both yielded layer 3 arrivals at the same geophone             position, once phantomed, the two values should lie at approximately the        same time. Arrival averaging would average the two values to produce a          single value for subsequent GRM processing.  To exclude an arrival from         averaging, assign it to layer 0.                                                                                                                                Arrival Interpolation: The procedure involves interpolating an arrival          time if one is missing at a geophone position. This fills in data gaps          caused if a geophone failed.                                                                                                                                    9.1  Sub-Menus:                                                                                                                                                 XY Analysis Menu: Used to set the start, increment and end XY values.           Layer Select Menu: Set the current working layer number. Note that when         layer 1 is selected, no interpolated arrivals will be displayed on              screen.                                                                         Control Menu: Used to set GRM parameters and the method of depth                migration.                                                                      Segment Menu: Define velocity variations or fix the velocity and XY of          a layer.                                                                        View Menu: Used to modify screen display parameters.                            Zoom Menu: Change the horizontal screen scaling.                                                                                                                9.2  Mouse Function:                                                                                                                                            The current segment, current layer velocity and XY value at the mouse           cursor position are printed in the right text column whenever a mouse           button is pressed.                                                                                                                                              9.3  Menu Items:                                                                                                                                                Update Function: Recalculate all analysis and redraw the screen.                                                                                                Thickness Function: A utility to calculate the distance between two             points.                                                                                                                                                                                                                                         9.4  GRM Analysis Procedure:                                                                                                                                    1. Complete the layer assignment and phantoming steps.                          1. Set the screen to display the XY and Velocity information.                   2. Select the optimum XY from the XY curves, and set the Optimum XY in          the Control Menu.                                                               3. Identify, from the XY curves, possible velocity changes in the               refracting layer, and define these intervals using the Segment Menu.            4. Manually set the layer 1 velocity, and any other layers above the            first refracting horizon on which GRM analysis will be performed.               Optionally use the intercept time method to determine the layer 1               velocity and thickness.                                                         5. Use the Control Menu to select the method of Depth Migration.                6. Display and check the Depth Section.                                                                                                                                                                                                                                                                                         This menu is used to define the ground surface elevation along the line.        Surface elevation information need not correspond to geophone positions,        or be evenly spaced (VIEWSEIS will perform linear interpolation between         known elevation points, as necessary).  All survey positions, however           must be sorted and entered in ascending order.                                                                                                                  10.1  Menu Items:                                                                                                                                               Entering data values: To begin entering values, point to a data line and        press the mouse button. Once a value has been entered, the Up and Down          Arrows keys can be used to move between values in a column. Similarly,          the Page-Up and Page-Down keys can be used.                                                                                                                     Load_ASCII: This option can be used to load files containing elevation          data in a format containing one line position and one elevation data            point per line.  This option provides an alternative to typing in each          value.                                                                                                                                                          Insert_Stn: Insert a line position and elevation value within the data          set.                                                                                                                                                            Delete_Stn: Delete a station elevation from the data set.                                                                                                       Spacing: As an alternative to typing in each line position, this option         can be used to create a set of evenly spaced line positions. (Note that         if the first line position is not zero when the Spacing option is               selected, line positions will increment from the non-zero starting              position.)                                                                                                                                                                                                                                      The Header Menu allows general text information to be entered and stored        in the VIEWSEIS file. Text information will be displayed on output plots.                                                                                                                                                                       This menu also presents information and utility functions which apply to        the entire seismic line.                                                                                                                                        11.1  Menu Items:                                                                                                                                               Shift Origin: This function can be used to shift the line origin, and           thus all geophone positions. This can be used, for example, to change the       geophone positions to a new survey grid origin.  For example, if geophone       1 is initially at line position 0, and needs to be shifted to new-              coordinate line position 120, select this function and enter in a shift         offset value of 120.                                                                                                                                            Reverse Viewing Angle: This function allows the angle of view to be             rotated 180 degrees.  For example, if the line was recorded from east to        west, the east-most geophone would be, by default, on the left side of          the screen. Reversing the viewing angle would place the west-most               geophone on the left side of the screen. To avoid confusion, it is              usually best to not use this option until all interpretation is                 performed, and only select it prior to plotting, if necessary.                                                                                                  11.1.1  Global Control Parameters:                                                                                                                              Units: The units of length for use throughout the program can be set and        changed using this option. Selecting this option switches the all length        parameters, and the units can be switched at any time during analysis or        plotting. (Units of time are always in milliseconds, and cannot be              changed)                                                                                                                                                        GRM Calculation Spacing: By default, GRM calculations are performed at          every geophone position. This option can be used, however, to interpolate       arrival times between geophone positions, allowing greater sensitivity          for XY Analysis. To interpolate arrivals, enter a number greater than 0.        For example, if the optimum XY is 7.5, and the geophone spacing is 5, a         GRM Calculation spacing of 2.5 would be appropriate.  It is usually best        to leave this option at 0 until XY analysis is being performed.                                                                                                 Arc Plot Increment: By default, one GRM arc is plotted for each GRM             calculation point (an arc plot increment of 0 or 1). To plot fewer arcs,        enter a larger number. For example, to plot an arc at every other               calculation point, enter 2.                                                                                                                                     Extrapolation: This option controls whether arrivals from all layers are        extrapolated out to the end of the seismic line.                                                                                                                11.1.2  Project Title and Location Information:                                                                                                                 Ten lines of text information specific to the seismic line can be stored        in this section.  Information such as the line name or number,                  orientation, and job number can be entered in this section, and later           stored in the VIEWSEIS file.  To begin editing, point and press a mouse         button.  Once a text line has been entered, the up and down arrow keys          can be used to move between lines.                                                                                                                                                                                                              The Help Menu system can be accessed from any menu within VIEWSEIS simply       by pressing the F1 key.  The help system is 'context sensitive', meaning        that the help information accessed depends upon which menu is displayed         at the time the F1 key is pressed. From within any Help Menu the Help           Index can be selected.                                                                                                                                          12.1  General Program Operation:                                                                                                                                1. Selecting Menus and Functions:                                               In general, the top lines of the screen contain menu and function names.        All menus and functions can be accessed by pointing, with the mouse, at         the menu name and pressing one of the mouse buttons. In addition, such          menus can be selected by typing the first letter of the menu name.                                                                                              2. Selecting items within the menus:                                            In a similar manner, the mouse is also used to select and modify items          within the menus.  When editing columns of numbers, the up and down arrow       keys can be used to move the editing cell between items.                                                                                                        3. Entering information in the VIEWSEIS editing line:                           When input is required from the user, the program displays the current          default setting within the editing line, which is a coloured or black on        white line. If the editor is invoked and the user immediately begins            typing text or numbers, the default setting is erased, and the new              information entered. If the first key pressed is the Home, End, Left or         Right Arrow, the default text remains on-screen for the user to modify.         Additional editing keys include;                                                       - Escape = abandons any editing changes                                         - Enter, Up or Down Arrow Key = accept editing changes                          - Control with left or right arrow = double cursor speed movement               - Delete and Backspace Keys = remove characters                                                                                                          4. Leaving menus and exiting the program:                                       The Quit Menu option displayed on the upper lines of the screen can be          selected with the mouse, by pressing the letter 'Q' or by pressing the          Escape key. (This will never end operation of the program, only exit from       menus.)                                                                                                                                                         To exit the program, continually select the Quit Menu option until the          Main Menu is reached, then select the 'File' Menu, and the Exit Program         option.                                                                                                                                                         The Layer Menu provides functions for assigning layer numbers to arrival        times and phantoming arrivals. Layer assignment and phantoming are              required before GRM analysis. Up to 9 layers may be defined, and bad or         unused arrivals should be assigned to layer 0.                                                                                                                  13.1  Sub-Menus:                                                                                                                                                Model Menu: To define a synthetic arrival time model.                           Zoom Menu: To zoom in on a section of the screen.                               View Menu: To change the screen display parameters.                             Repick Menu: To re-load the trace data corresponding to the currently           selected shot.                                                                  Option Menu: Functions for re-numbering layers and writing shot                 velocities to external files.                                                                                                                                   13.2  Mouse Function:                                                                                                                                           Right Mouse Button: When the right mouse button is pressed, the closest         arrival time becomes the 'Selected' arrival. (Information about the             selected arrival is printed in the right text column, if the column is          shown on-screen.)  Layer assignment and phantoming functions always refer       to the 'Selected' arrival.  Once selected, the arrival is assigned to the       next number key pressed.                                                                                                                                        Left Mouse Button: The left mouse button is used to specify the                 phantoming time shift. The time shift is always calculated relative to          the reference arrival.  Caution should be used when pressing the mouse          button, because each press will define a new phantom value.  If there is        no selected reference arrival,  the first press of the left button              defines the reference arrival. The "Show Phantomed" option must be set          to "Y" in the View Menu for this option to work.                                                                                                                13.3  Menu Functions:                                                                                                                                           Numbers keys 0 through 9: The selected arrival is assigned to a layer by        typing the corresponding number key. Note that Layer 0 is for all bad           data and un-assigned arrival times, Layer 1 for direct wave arrivals, and       Layer 2 through 9 for refracted energy arrivals.                                                                                                                Left and Right Arrow Keys: The arrow keys move the mouse cursor to the          next arrival time of the current shot.                                                                                                                          Update: The function redraws the screen, and updates the position of all        regression lines.                                                                                                                                               Clearphnt: This option clears any phantoming of the current arrival             selection.                                                                                                                                                      Select_ref: select the reference arrival, providing a reference for time        shifts.                                                                                                                                                                                                                                         13.4  Phantoming within the Layer Menu                                                                                                                          The Layer Menu provides functions for the phantoming, or time shifting,         of the arrival times. The purpose of Phantoming is to construct a               complete and continuous set of forward and reverse arrivals along the           seismic line (ie. the arrivals from each adjacent shot are matched up).         Phantoming can be performed on forward and reverse shots, and separately        on the forward and reverse components of mid shots. All assigned arrivals       must be phantomed, or re-assigned to layer 0.  If more than one arrival         from a particular layer is available at a specific geophone position,           they will be averaged upon entry into the GRM Menu.                                                                                                             Important: Complete phantoming of arrivals from each layer is essential         prior to GRM Analysis.                                                                                                                                          13.5  Phantoming Procedure:                                                                                                                                     Step 1. Setting up the screen for phantoming:                                   Use the View Menu to set the following display parameters -                     - Show only the arrival time data                                               - Show only phantomed data.                                                     - Begin by showing only forward and mid shots, later only reverse and           mid.                                                                            - Show only the layer number of interest.                                       - Set the 'Symbol By' option to 'Shot'.                                                                                                                         Step 2. Selecting a Reference Arrival:                                          The phantoming of a shot is performed relative to a Reference Arrival,          and any arrival within a shot can be used as a reference.  To select the        Reference Arrival, point close to it and press the left mouse button. For       example, to phantom the layer 3 arrivals of shot 10, select any one of          the layer 3 arrivals of shot 10 as the reference.                                                                                                               Step 3. Phantoming:                                                             Once the reference arrival is selected, whenever the right mouse button         is pressed the reference arrival (and all arrivals from that shot with          the same layer number) will be phantomed to that time. The mouse can be         repeatedly moved and clicked to allow fine adjustment of the position.          Once the phantoming is completed for a particular shot, Step 2 is               repeated to select a new shot, and phantoming continues along the line.                                                                                         13.6  Phantoming Notes:                                                                                                                                         Phantoming Mid Shots:                                                           The forward component of a mid shot can be phantomed independently of the       reverse section of the mid shot.  Note that all assigned arrivals must          be phantomed prior to GRM analysis.                                                                                                                             Using Phantoming During Layer Assignment:                                       The Phantom function can be used to aid layer assignment. If layers             cannot be clearly identified by a constant slope, patterns observed in          overlapping shots can be used to determine which arrivals are associated        with each layer.  For example, similar patterns in the near and long            offset shots can indicate which arrivals are refracted from the same            layer. If the long offset shot is phantomed down to the near offset shot,       these patterns can be closely compared.                                                                                                                                                                                                         The Layer Options Menu provides functions for working with arrival time         data.                                                                                                                                                           14.1  Menu Items:                                                                                                                                               Re-Number: This function allows global changes to a particular layer            number.                                                                         To insert a layer, for example, begin by re-numbering all layer 3               assignments to layer 4, and then selectively re-assign some of the layer        4 arrivals back to the new layer 3.                                             To delete or merge a layer, for example, re-number all layer 4 to layer         3.                                                                                                                                                              Write: This function writes the velocity information from the current           selection into an ASCII file called Vel.dat in the current directory.                                                                                                                                                                           The VIEWSEIS Main Menu provides access to the various arrival time              analysis functions.  Help information is available by pressing F1.                                                                                              15.1  Sub-Menus:                                                                                                                                                File Menu: Load or save an interpretation file, set program                     configuration.                                                                  Data Menu: Load or edit shot data, ground surface, file header or control       data.                                                                           Layer Menu: Assign layer numbers to arrival times and perform phantoming.                                                                                       GRM Menu: Access to the various GRM analysis functions.                         Output Menu: Create paper copy output, and export data to ASCII files.          Zoom Menu: View a larger or smaller portion of the screen.                      View Menu: Change the screen display and scaling parameters.                                                                                                    15.2  Mouse Function:                                                                                                                                           When arrival time information is displayed on screen and a mouse button         is pressed, information from the closest arrival is displayed in the            right hand text column. This information includes the Shot name, geophone       line position, arrival time, layer number assignment, velocity, intercept       time and R^2 value from regression analysis, and finally, approximate           layer thicknesses calculated using Intercept Time equations for non-            dipping layers.                                                                                                                                                                                                                                 The Model Menu allows the user to create a set of arrival times based on        defined layer thicknesses and velocities.                                                                                                                       Up to two separate model cases (A and B) can be created, and then               compared graphically on screen. Any configuration of shot and geophone          positions, number of layers, layer thicknesses and velocities can be            defined. Depending on the parameters, a forward, mid or reverse shot will       be created. In addition, the theoretical GRM XY is displayed for each           defined layer.                                                                                                                                                  Defining the Model:                                                             Prior to creating the model, first set the Show Arrivals and Show Model         parameter in the View Menu to 'Y'.  Once set, simply enter all the              parameters in Model Menu, and then exit to the graphics screen to review        the calculated arrivals.                                                                                                                                        16.1  Menu Items:                                                                                                                                               Number of Geophones: Specify either 12 or 24 geophones.                                                                                                         Geophone Spacing: During survey design, the geophone spacing can be             varied to show how the refracted layer arrivals will be recorded. To            create a model of a reverse shot, enter a negative geophone spacing.                                                                                            Geophone 1 Position: Generally set to 0, but the geophone 1 position can        be set to any line position to overlay the model over actual field data.                                                                                        Shot Position: The shot position can be placed at any point along the           line, simulating near and long offset shots, and forward, mid or reverse        shot directions.                                                                                                                                                Velocity: Enter the estimated velocity for each layer, including the            deepest refracting layer. Use metres/sec or feet/second, depending on the       units set in the Header Menu.                                                                                                                                   Layer Thickness: Enter the estimated thickness of each of the layer above       the deepest refracting layer. Use either feet or metres, and be                 consistent with the those set for the velocity, and set in the Header           Menu.                                                                                                                                                                                                                                           16.2  Model Applications:                                                                                                                                       Field survey design:                                                            The model can be used to check the geophone spacing and shot offsets            required to record sufficient refracted arrivals from each layer. A             refracted arrival must be recorded at each geophone position, and from          each layer interface, along the line.                                                                                                                           Hidden layer analysis:                                                          The model can indicate if refracted arrivals will be recorded from all          suspected subsurface layers.  If a layer is too thin, or of too low a           velocity contrast to be detected by refraction, the model will not show         any arrivals from that layer\.                                                                                                                                  Layer Assignment:                                                               Comparison of the model to actual arrivals can indicate the number of           layers, and which arrivals should be assigned to those layers.                                                                                                  16.3  Model Notes:                                                                                                                                              - To suppress the display of the model, enter a geophone spacing of 0,          or change the Model option in the View Menu.                                    - All calculations are for horizontal layers.                                   - The lines linking the model arrivals are dashed in the region where           shot and geophone geometry make it impossible to record arrivals from           that layer.                                                                     - To create a mid shot model, place the shot position within the geophone       line range.                                                                                                                                                                                                                                                                                                                     The Output Menu provides access to the various plotting and data export         functions.                                                                                                                                                      17.1  Sub-Menus:                                                                                                                                                Plot Menu: To create a paper copy plot of the data.                                                                                                             Borehole Menu: To define borehole information for display on the section.                                                                                                                                                                       Export Menu: Selecting the Export function creates an ASCII file                containing all the shot data and layer interpretations. The ASCII file          is always created with the same root name as the current VIEWSEIS file          and a file extension of '.prn'. The file can be directly loaded into            Lotus 123 using the File Import Numbers procedure.                                                                                                                                                                                              The Pan Menu provides functions for moving the screen window to display         other portions of the seismic line.                                                                                                                             18.1  Mouse Function:                                                                                                                                           To pan the display window, first point to a reference point on the              screen, then press and hold the left mouse button while dragging the            mouse to a new position. While holding the button, a dotted line will           indicate the distance and direction the screen window will move.                                                                                                                                                                                The Pan Trace Menu is used to move the display window to another portion        of the trace data. The pan function can be used to change both the time         window and which traces are displayed on the screen.                                                                                                            19.1  Mouse Function:                                                                                                                                           To pan the display window, first point to a reference point on the              screen, then press and hold the left mouse button while dragging the            mouse to a new position. While holding the button, a dotted line will           indicate the distance and direction the screen window will move.                                                                                                                                                                                The Pick Menu provides functions for the display of seismic traces, first       break picking and layer assignment.                                                                                                                             20.1  Sub-Menus:                                                                                                                                                Zoom Trace Menu: To zoom in on a smaller time window, or fewer traces.          Scale Trace Menu: Allows the interactive adjustment of the trace scales.        Pan Menu: To shift the screen window in time or across the traces.              Auto Pick Menu: To automatically pick first arrivals.                           Quit: To accept the first break picks, and return to the Trace Load Menu.                                                                                       20.2  Mouse Function:                                                                                                                                           Arrival times are picked by pointing and pressing the mouse button.             Pressing the left button draws a cross hair on screen prior to making the       pick. Picking with the right button is slightly quicker, as no cross            hairs are drawn prior to making the pick. To increase pick accuracy, make       the time window smaller using the Zoom Trace Menu.                                                                                                              20.3  Menu Items:                                                                                                                                               Assigning Layer Numbers: An arrival can be assigned to a layer by               pointing to the trace and pressing the number key corresponding to the          layer number.  It is not necessary to press the mouse button, only point        and type the layer number.  Following a layer assignment, each newly            picked arrival will be assigned, by default, to the same layer number.                                                                                          Left and Right Arrow keys: The left and right arrow keys can also be used       to move the cursor between traces.                                                                                                                                                                                                              The Plot Control Menu allows the user to set the appearance of the paper        output. The default setup for the plot control menu is based on the last        on-screen settings prior to the menu call.                                                                                                                      21.1  Output Procedure:                                                                                                                                         Step 1. Set the screen to display the correct plot information:                 Output begins by using the View Menu the display desired information.           Once the screen parameters are set, the user enters the Plot Control            Menu.  If necessary, the Reset function can be used to reset the plot           parameters to the screen parameters.                                                                                                                            Step 2. Create a plot file:                                                     The second step is to create an output file which contains all the plot         information.  Output files have the extension '.plt', and are device            independent (except for page size).  The output file is created when the        GO function is selected in the Plot Control Menu.                                                                                                               Step 3. Send the plot file to the printer or plotter:                           Once the output file is created, the program enters the Plot File Control       Menu, from which the output file may be pre-viewed, and sent to a printer       or plotter.                                                                                                                                                     21.2  Menu Items:                                                                                                                                               Reset : Select this option to reset the output parameters to the current        screen parameters.                                                                                                                                              Go: Select this option to create output with the current settings.                                                                                              Save: This saves the plot configuration in the file vsplot.cfg.  This           option allows plot configurations to be moved between plot files. The           plot configuration is also automatically saved in the VIEWSEIS 'vs' file.                                                                                       Load: This loads the plot configuration from the file vsplot.cfg.                                                                                               21.3  Plot Control Parameters                                                                                                                                   The upper portion of the Plot Menu contains rows matching the type of           output data (Arrivals, XY Analysis, etc.).  The plotting range, scale,          and plot format parameters can be set for each data type.  The lower            portion of the screen presents the page size parameters.                                                                                                        21.3.1  Data Parameters:                                                                                                                                        Plot?: This controls whether the corresponding information will be              output. For example, if you wish to plot the arrival time data, set the         Plot? parameter in the Arrivals row to Yes.                                     Data Start, Stop: The lower and upper data bounds of the output.                Scale: The scale at which the data will be plotted. If the Scale value          is set to 0.0, all the data within the Start-Stop range will be plotted         at a scale appropriate to fit the row size.                                     Axis Increments (Grid, Label, Tick): These values control the format of         the grid lines, data axis labels, and axis ticks.  Set the value to 0           suppress the output.                                                                                                                                            21.3.2  Page Parameters:                                                                                                                                        Output Device Number: Four default page settings are available.                 Page Width: The page length corresponding to the horizontal seismic line.                                                                                       Page Height: The page size available for the various rows of data.              Plot Rotation: Controls the orientation of the plot on the page.                Plot Margins: The margin between the edge of the paper and the data.            Number of Pens: The number of pens, and thus colours, available.                Plot File Name: The file name into which the plot parameters will be            written.                                                                        Plot File Type: Controls whether the plot file is in ASCII or Binary            format. Binary files are smaller and processed faster. ASCII files may          be modified by the user.                                                        Row Dimensions: The dimensions of the data rows, and spacing between            rows.                                                                           Plot Device Configuration: This shows the default plot device, and page         size.                                                                                                                                                                                                                                           The Plot File Control Menu provides functions to pre-view and print the         plot files. The program enters this menu after creating a plot file.                                                                                            22.1  Sub-Menus:                                                                                                                                                Shell: Selecting this option starts a DOS shell, from which DOS commands        may be entered. To exit the shell and continue processing, type "exit"          at the DOS prompt, and press enter.                                                                                                                             22.2  Menu Items:                                                                                                                                               22.2.1  Plot Options:                                                                                                                                           1. Set the plot.exe path, and install a plot device:                            This option allows the user to specify the directory in which the               plot.exe file is located. Normally, this directory is specified during          program installation (run VIEWSEIS /i).  In addition, the brand of output       device, port and page size are specified with this option.                                                                                                      Note for CAD Interface: To send a plot file to a CAD system, select the         DXF file output device instead of a printer, and then load the DXF file         into your CAD system.                                                                                                                                           This option is also available from the DOS command line by typing plot          /i <enter>.                                                                                                                                                     2. Rename the plot file:                                                        This function allows the plot file to be renamed.                                                                                                               3. Preview the plot file:                                                       The Preview option draws an exact copy of the output file on-screen,            allowing a quick check of the plot. This command is available from the          DOS command line by typing view filename.plt <enter>.                                                                                                           4. Send the plot file to the printer or plotter:                                Select this option to begin output of the plot file. This command is            available from the DOS command line by typing plot filename.plt <enter>.                                                                                                                                                                                                                                                        The Scale Trace Menu provides functions for interactive adjustment of the       seismic trace scales.                                                                                                                                           †îþP  Mouse Functions:                                                                                                                                          Left Mouse Button: To increase the trace scale value (and make the              seismic data appear smaller on the screen), point to a trace and press          the left button. If a group of traces have been defined, the scale of all       the traces in the group will be changed.                                                                                                                        Right Mouse Button: To reduce the scale value (and make the seismic             response appear larger) point to a trace and press the right button. If         a group of traces have been defined, the scale of all the traces will be        changed.                                                                                                                                                        23.2  Menu Items:                                                                                                                                               Group: To simultaneously change the scale of a group of traces, first           select the Group option, and then define a window to include the desired        traces. A window is defined in a similar manner to the Zoom Trace Menu.                                                                                         Clear_Group: Select this option to clear the trace group, and return to         individual trace scale adjustment.                                                                                                                                                                                                                                                                                              The Segment Menu is used to define intervals in the seismic line which          have similar velocity or XY.  Up to 20 segment lines can be added and           removed within each layer.  Segment editing depends upon which layer is         current at the time. The Segment function allows the velocity and XY to         vary along the seismic line.                                                                                                                                    24.1  Sub-Menus:                                                                                                                                                Velocity Input: Allows the user to fix the velocity within a segment of         the seismic line.                                                               XY Input: Allows the user to define a different XY within a segment.                                                                                            24.2  Mouse Functions:                                                                                                                                          Adding a segment line: Segments are added by pointing to the desired line       position and pressing the left mouse button.                                                                                                                    Removing a segment line: To remove a segment, point to it and press the         right mouse button.                                                                                                                                             24.3  Velocity Analysis and Segment Lines:                                                                                                                      During GRM analysis, the layer velocity is calculated from the inverse          of slope of the Optimum XY line.  If the slope of the line becomes              steeper (or shallower) over a number of geophone positions, this                indicates that the velocity of the refracting layer is decreasing (or           increasing) over the line. Segment lines should then be added at the            beginning and end of the zones where the slope changes.                                                                                                         It is possible to manually fix the velocity of all or a portion of the          line using the segment menu.  This is done by first dividing the seismic        line into zones,  and then selecting the Velocity Input Menu. Within this       menu, the segment zone and velocity are set.                                                                                                                    Similarly, the user can vary the XY value along the line. Again, first          define a segment zone, and then select the XY Input Menu to fix the XY          value within that zone.                                                                                                                                                                                                                         The Shot Menu presents an overview of the various shots associated with         a particular seismic line.  Arrival times are organized by shot.                                                                                                25.1  Mouse Function:                                                                                                                                           Clicking the mouse button while pointing at a shot name directs the             program to the Edit Shot Menu, where shot parameters and arrivals can be        edited, and traces loaded for first break picking.                                                                                                              25.2  Menu Items:                                                                                                                                               Next_Page: Display the next page of shot names.                                                                                                                 Delete: Delete a single shot and its arrivals from memory.                                                                                                      Display: Clicking on the Display column will toggle subsequent display          of the shot. This parameter is usually set in the View Menu, using the          Show Forward, Reverse and Mid option.                                                                                                                           Shot Name: The shot name is usually set to the trace file name from which       the first break picks were made. It is not necessary to have shots loaded       in any particular order. The shot number is not important.                                                                                                      25.2.1  Entering Arrival Time Data:                                                                                                                             To edit an existing shot: Point at one of the shot names and press the          right mouse button.                                                                                                                                             To create a new shot: Press the mouse button while pointing to any blank        shot.  This will direct the program to the Shot Edit Menu, in which             arrivals may be entered.                                                                                                                                        To make first break picks: Create or edit a shot, and then select Trace         Load from the Shot Edit Menu.                                                                                                                                   Shot parameters and arrival times are entered and edited in the Shot Edit       Menu. The Next Shot and Previous Shot functions can be used to view other       shots associated with the seismic line.                                                                                                                         26.1  Sub-Menus:                                                                                                                                                Trace Load Menu: Load a digital seismic trace file, for picking first           break arrival times.                                                                                                                                            26.2  Menu Items:                                                                                                                                               Shot Number: This is only a reference number; the order of the shots in         the file is not important to the program.                                                                                                                       Shot Title: The default shot title is the name of the seismic file from         which the arrivals were picked.                                                                                                                                 Number of Geophones: This can be toggled between 12 and 24.                                                                                                     Shot Line Position: This is the LINE position where the shot was fired.         This is NOT the distance between geophone 1 and the shot.                                                                                                       Shot Direction: The Shot Direction conforms to the convention outlined          below. The shot direction can be used in conjunction with the Geophone          Spacing parameter to calculate evenly spaced geophone positions.                                                                                                        Forward Shots: Shot Position less than or equal to Geophone 1                   Position  (Geophone numbers increase as line position increases).               Note that geophone 1 is always closest to the shot.                             Mid Shots: Geophone 1 Position < Shot Position < Geophone 12/24                 Position (Geophone numbers increase as line position increases)                 Reverse Shots: Geophone 1 Position less than or equal to Shot                   Position  (Geophone numbers DECREASE as line position increases).               Note that geophone 1 is always closest to the shot.                                                                                                     Geophone Spacing: This option can be used to set the geophone line              positions for the entire set of arrivals. The geophones need not,               however, be at a uniform spacing although uniform is preferred. To use          this option, first set the Shot Direction, then specify the geophone 1          position. Finally, set the geophone spacing. When set, the program will         calculate to line positions for the remainder of the geophones.                                                                                                 Geophone Position: This is the line position of the geophone. Note that         for forward and reverse shots, geophone 1 is always closest to the shot.                                                                                        Arrival Time: The first break arrival time in milliseconds.                                                                                                     26.3  Notes:                                                                                                                                                    Line Position Units: The distance units (feet or metres) are set in the         Header Menu. When entering data, work in the same units and line position       as those used in the field. When analysis is complete, and prior to             plotting, you may then switch the units, survey coordinate system and           line viewing angle in the Header Menu.                                                                                                                          Data Display Errors: Display and Regression line errors are usually             caused by errors in the shot parameters.  Check these parameters                carefully!!!                                                                                                                                                                                                                                    The Trace Display Menu provides functions for controlling the display of        the raw seismic traces, as well as the current parameter settings for the       shot. Note that the original trace data file will never be altered by           functions in this menu, as all operations are performed only on data in         RAM memory.                                                                                                                                                     27.1  Menu Items:                                                                                                                                               Polarity: This option will reverse the polarity of the traces.                                                                                                  Global_scale_change: This option is used to change all the trace scale          values by a fixed value. Lower scale values make the trace appear larger        on-screen.  To change the amplitude, enter an operator, and then a value.       For example, to double the scale value of each trace, enter *2. To set          all the values to be equal to 25, for example, enter =25.                                                                                                       Unload_trace: Used to remove one or more traces from memory. This could         be used, for example, if shot data was recorded on channels 12 through          24, leaving channels 1-12 blank. Traces 1-12 would then be unloaded.                                                                                            Swap: This function is used to reverse the order of the traces, so as to        follow the Forward, Mid and Reverse direction convention (see below). For       example, if trace 1 is furthest from a reverse shot, the traces must be         swapped to follow the standard VIEWSEIS format in which trace 1 is              closest to the shot.                                                                                                                                            27.1.1  Trace Display Information:                                                                                                                              Show Trace as: Options to draw the trace as wiggle or variable area.                                                                                            Clip Trace: Controls whether trace values above the scale value are             displayed.                                                                                                                                                      Show Layer numbers: Prints assigned layer numbers beside the picks.                                                                                             Show Regression Lines: Draws layer regression line on-screen when               updated.                                                                                                                                                        Show Text Column: Prints layer and arrival information on-screen.                                                                                               Centerline: Draws a vertical line at the zero amplitude of each trace.                                                                                          27.1.2  General Shot Information:                                                                                                                               For a detailed discussion of the shot parameters, see the help                  information associated with the Shot Edit Menu.                                                                                                                 Trace Scale: The amplitude level of the left and right trace column             margins. Larger scale values make the trace appear smaller on screen. The       default value is twice the mean amplitude of the trace.                                                                                                                                                                                         The Trace Load Menu allows the user to load seismic traces or first break       pick files directly into VIEWSEIS.  A number of formats are supported,          including the various trace files, and binary or a ASCII pick files.                                                                                            When a trace file is loaded, the program will display the traces on             screen, allowing the user to set or edit the first break picks.                                                                                                 28.1  Menu Items:                                                                                                                                               28.1.1  File Loading Parameters:                                                                                                                                Creating/Replacing Shot: Select this option to change the shot number           which will be either replaced or created. This will automatically               increment as multiple trace files are loaded.                                                                                                                   Free Memory for Traces: This value can be used to determine if the entire       trace file can be loaded into DOS conventional memory. If insufficient          conventional memory is available, the program will then attempt to load         the data into LIM 4.0 expanded memory, if available. If expanded memory         is not available, the program will load as much of each trace as                possible.                                                                                                                                                       The amount of memory required, in KB, to load a trace file can be               calculated from the following equation: 4 *(number of samples per trace)        * (number of traces + 1) / 1024.  All values are stored as single               precision reals.                                                                                                                                                28.1.2  Available Data Formats:                                                                                                                                 Select, with the mouse, the seismograph format corresponding to the trace       file which will be loaded.                                                                                                                                                                                                                      The Velocity Input Menu allows the user to define, and thereby fix, the         layer velocity within a segment.  The layer velocity which is fixed             depends upon the current GRM Layer setting.                                                                                                                     Defining a segment velocity:                                                    To explicitly fix the velocity within a part of the seismic line, first         pick the segment range by placing the mouse within the segment and              pressing a mouse button.  Once the segment is selected, enter in the            velocity.                                                                                                                                                       Resetting the segment velocity:                                                 To reset the velocity within a segment to the default calculated from XY-       Velocity Analysis, first select the segment with the mouse, and then            enter a velocity of 0.                                                                                                                                                                                                                          The View Menu controls the manner in which data is displayed on-screen.                                                                                         30.1  Menu Items:                                                                                                                                               30.1.1  Arrival Time Data:                                                                                                                                      Show Arrival Times: Controls whether arrivals are displayed. In addition,       the user can control whether phantomed, unphantomed or model data is            displayed.                                                                      Display Shot Type: Used to show or hide all shots of a particular type          (forward, mid or reverse).                                                      Show Layer: Used to show or hide arrivals assigned to a particular layer.                                                                                       Symbol By: Controls the arrival time symbols.                                           Shot = draw all arrivals from the same shot with the same symbol.               Layer= arrivals assigned to the same layer have the same symbol.        Link: draw dotted lines between arrivals associated with the same shot.         Minimum: the time corresponding to the lower screen boundary                    Maximum: the time corresponding to the upper screen boundary                                                                                                    30.1.2  XY-Velocity Analysis:                                                                                                                                   This option allows the display of the velocity analysis curves. Each            layer is presented separately, and the range of XY values is set in the         Control Menu.                                                                                                                                                   Show as residual: this directs the program to remove a linear trend from        the XY-velocity analysis curves, and only display the residual variation        about the line. Any variation in XY will become more apparent when the          curves are displayed as a residual.                                                                                                                             30.1.3  Layer Velocities:                                                                                                                                       Displays the all the layer velocities, calculated from the XY-Velocity          Analysis curves. Units are in metres per second or feet per second,             depending on the units setting in the Header Menu.                                                                                                              30.1.4  Time-Depth Section:                                                                                                                                     The Time-Depth Section is analogous to a geologic cross section, however        instead of units of depth, the vertical units are time (in milliseconds).       One Time-depth curve is presented for each XY value displayed. The range        of XY values set in the Control Menu.                                                                                                                           Show Symbols: display symbols at each XY point, if set to "N", only lines       are drawn.                                                                                                                                                      Important: The scale minimum and maximum correspond to the lower and            upper scale values in the screen window. For this reason, set the to            create a time section with the scale values increasing downward, set, for       example, the minimum value equal to 100, and the maximum value equal to         0. (ie. minimum  greater than maximum).                                                                                                                         30.1.5  Depth Section:                                                                                                                                          The final migrated depth section, showing layer interfaces below the            ground surface, can be displayed. The method of depth migration is set          in the Control Menu, and the units set in the Header Menu.                                                                                                      Show Borehole Data: controls whether information entered in the Borehole        Menu is shown on screen.                                                                                                                                        Minimum: The depth value (elevation) of the bottom of the screen window.        Note that depth below ground surface is negative. Ground elevation values       can be entered in the Ground Surface Menu.                                                                                                                      30.1.6  Station Scaling:                                                                                                                                        Left/Right Margin: The station position corresponding to the left/right         screen boundaries. The Zoom function can also be used to change these           values.                                                                                                                                                         30.1.7  Other Display Options:                                                                                                                                  Show Text Column: controls whether a column of text information is              displayed along the left hand side of the screen.  Arrival selection and        other text information can be displayed along side the graphical data.                                                                                          Display Configuration: The program allows up to four screen display             configurations to be set, stored and recalled. For example, configuration       1 could be used during layer assignment, and configuration 2 could store        the screen set-up for XY and Velocity analysis.  To switch between              configurations, click the mouse button on this option.                                                                                                                                                                                          The XY Input Menu allows the user to define, and thereby fix, the XY for        use within a segment.  This menu allows the XY value to vary between            segments within the seismic line.                                                                                                                               Setting the segment XY:                                                         To set the XY for a segment, first point within the segment and press a         mouse button.  Once a segment has been selected, enter in the XY value          for use in subsequent GRM depth migration calculations.                                                                                                         Resetting the segment XY:                                                       To reset the XY within a segment, first select the segment with the             mouse, and then enter an XY of 0.  When the Segment XY has been reset to        zero, the Optimum XY (set in the Control Menu) will again be used for GRM       calculations within the segment.                                                                                                                                                                                                                The XY Menu can be used to set the range of the XY calculations for each        layer. The purpose of this analysis is to determine the optimum XY              spacing, and check if the velocity of the refracting layer varies along         the line. During XY analysis, the user compares the calculations for            various XY spacings, selects the optimum value, and then sets this in the       Optimum XY column of the Control Menu.  This is performed for each GRM          layer.                                                                                                                                                          The XY range can also be set in the Control Menu.                                                                                                               32.1  Menu Items:                                                                                                                                               Start: This is the first XY spacing that will be used in the                    calculations.                                                                                                                                                   Increment: This is the amount that the XY will increase between                 calculations.                                                                                                                                                   End: The XY value after which calculations will stop.                                                                                                           32.2  Guidelines for selecting the optimum XY:                                                                                                                  The optimum XY value should be selected based on the following two              observations:                                                                                                                                                   1. The optimum XY creates the XY-velocity analysis curve showing the            minimum variation along the seismic line.                                                                                                                       2. The optimum XY creates the time-depth curve showing the maximum              variation and detail along the seismic line.                                                                                                                                                                                                    The Zoom Menu can be used to change the screen scaling.                                                                                                         33.1  Sub-Menus:                                                                                                                                                Pan Menu: To pan the screen window to a new section of the seismic line.                                                                                        33.2  Mouse Function:                                                                                                                                           To create a zoom window, press and hold the left mouse button while             dragging the mouse. A box indicating the new window size will be created        while the mouse is moved.                                                                                                                                       33.3  Menu Items:                                                                                                                                               All: Selection of this option will direct the program to display the            entire seismic line, and if arrivals are displayed, all the arrival data.                                                                                       Spread: After selecting the Spread Option, the user will be requested to        point to a spread and click the mouse. The program will then set the left       and right screen borders to the first and last arrival from that spread.        The Zoom Spread function can be used to quickly pan to the left or right        of the current screen, by selecting a spread to the left or right of the        current spread.                                                                                                                                                 Last: This sets the view window to the last set of display parameters.                                                                                          Border: This function allows the user to pick, with the mouse, the left         and right screen borders.                                                                                                                                                                                                                       The Zoom Trace Menu is used to change the time window and number of             traces displayed on screen.  For example, if 24 traces were displayed on        screen, the zoom function could be used to focus in on only 8 or 12             traces.                                                                                                                                                         34.1  Mouse Function:                                                                                                                                           To create a zoom window, press and hold the left mouse button at the            upper corner of the zoom window, and while holding down the button, drag        the mouse. A box indicating the new window size will be created while the       mouse is moved. When the button is released, a smaller window will be           created.                                                                                                                                                        34.2  Menu Items:                                                                                                                                               All: Select this option to display all the traces data.                                                                                                         Last: Displays the previously selected zoom window.                                                                                                             Enter_values: Allows the user to directly enter the start and stop time         window.                                                                         