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            Tutorial

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This tutorial describes step by step how to work with the program SurGe. It is assumed, in this tutorial, that you have installed the last version of SurGe including the SurGe Project Manager.

Content

• Chapter 1: Basic operations
  • How to read and display simple input data
  • How to create a surface
  • How to display a created surface
  • How to calculate and display isolines
  • How to display a 3D view of a surface
• Chapter 2: Interpolation / approximation parameters
  • How to change interpolation / approximation parameters
  • How to obtain sharp interpolation
  • How to obtain smooth interpolation
  • How to obtain smooth approximation
  • How to obtain trend surface
  • How to utilize trend surface for improving extrapolation
  • How to interpolate terrain data
  • How to filter input data
  • How to use different modes of interpolation
• Chapter 3: Digitization
  • How to digitize points
  • How to digitize a boundary
  • How to digitize spatial polylines
  • How to digitize faults
  • How to create and display cross-sections
  • How to measure horizontal distance
  • How to digitize isolines
  • How to digitize a background
• Chapter 4: Grids
  • How to create an ASCII grid
  • How to import other map/GIS grid formats
  • How to utilize an existing grid
  • How to directly convert seismic reflection times to structure depth
  • How to combine interpolation and approximation
  • How to modify the size and the shape of the grid area
  • How to perform mathematical calculations with grids
  • How to simulate wedging out of layers
  • Maps of thiskness and volume calculation
• Chapter 5: Print
  • How to print map
  • How to print isolines
  • How to print cross-section
  • How to create PostScript print
    

Chapter 1: Basic operations

How to read and display simple input data

The program SurGe.exe needs basic input data in an ASCII file containing point coordinates XYZ. Other input data (boundaries, faults, spatial polylines, ...) are optional. The basic input data must contain at least two different XYZ points with different z-coordinates.
In this section we will use the file EX1.DTA, which is stored in the directory EXAMPLES. The file is identical with the following list:

# Input data - example 1
608.400  116.800  209.356  LB01
 29.800   23.300  196.790  LB02
190.500  166.600  203.735  LB03
358.000  538.500  224.650  LB04
487.800  449.400  205.038  LB05
961.800  480.800  200.520  LB06
137.900  396.500  217.890  LB07
545.836  248.764  208.320  LB08
741.158   11.243  224.570  LB09
424.061  306.638  198.340  LB10
902.721   58.265  208.030  LB11
655.554  570.684  201.530  LB12
806.266  592.387  200.520  LB13
774.918  351.248  254.650  LB14
369.805  213.799  198.060  LB15
305.903  117.344  197.340  LB16
216.682   57.059  196.930  LB17
501.464  356.237  199.570  LB18
765.102  118.346  209.050  LB19
695.073  148.211  209.050  LB20
646.671  206.911  209.050  LB21
869.115  142.032  209.050  LB22
948.412  217.210  209.050  LB23
401.570  263.552  198.230  LB24
577.672  409.789  200.440  LB25
641.522  445.833  200.070  LB26
235.767  606.487  245.370  LB27
 46.277  532.339  200.310  LB28
482.927  602.368  250.360  LB29
160.589  282.089  230.980  LB30

Each row of the XYZ file contains data related to one point. The first three items in each row of the XYZ file must contain x, y and z coordinates of the point and the fourth item must be a label for the point - character string containing 1-23 characters. Items in the row must be separated by at least one space. If the character  #  is in the first column of a row, the row is ignored and can be used as a comment. The XYZ file is an ordinary ASCII file and can be edited with any ASCII editor.
Important warning: Do not save the data file in unicode format. SurGe cannot read unicode format!

To start the program SurGe.exe for input file EX1.DTA, select the project Example 1 and the map The first example map in the SurGe Project Manager and press Run SurGe button.
Immediately after the start SurGe.exe reads input file and displays points XYZ in blue color. Now you can use two useful shortcut keys - K, which displays z-coordinates of  XYZ points and N, which displays their labels. If you press Alt+S, points (and labels and / or z-coordinates, if they are displayed) will be displayed in colors indicating their z-values.  
To move displayed objects (now only points) you can use cursor keys. If you use cursor keys with key Ctrl, only moved points are displayed (without labels and z-coordinates).
To zoom map, use key PgUp (zoom-in) or PgDn (zoom-out). Again, you can use key Ctrl with these keys. Step of moving and zoom can be changed with shortcut keys "1", "2", "3", "4" or "5".
To have better orientation in the map, you can display a map mesh with labels (by Ctrl+E) or without labels (by Ctrl+S).
Key R can be used for restoration of the basic display (without labels, z-coordinates, isolines, map mesh, ...). Using Ctrl+R you can change background color (which is by default black) between black and white.


How to create a surface

Let us suppose, you need to calculate a surface passing through points given in file EX1.DTA. Start the program SURGEF.EXE using the menu item Interpolation / Calculate grid (or press the shortcut key F3). SURGEF.EXE is a console application written in FORTRAN. It reads the parameter file PAR.3D, which is created by SurGe.exe. This file contains information about the input data file name, interpolation parameters and so on.
The program SURGEF needs to enter some information. The default values (calculated internally by SURGEF) are enclosed in brackets - if you agree with the default value, simply press Enter.
If there is a file EX1F.GRA (binary file containing previously computed grid),  SURGEF asks, if it has to be read:

READ FILE .GRD? (Y/N) [N]

This feature has a special application, which will be explained later. So press Enter.
The next information to be entered is grid size in direction x; the program SURGEF computes this size internally so that a precise interpolation can be achieved:

GRID SIZE IN X-DIRECTION (MIN. 19) [100]:

Press Enter because this value is suitable for good interpolation. The next input corresponds to the grid size in direction y:

GRID SIZE IN Y-DIRECTION (MIN. 12) [ 64]:

You should not change this value, so press Enter.
The next query is:

GRID SIZE ENLARGEMENT [ 24]:

This value defines the number of grid rows and columns, which has to overlap the interpolation area. The value 10-50 will improve the shape of the surface at the border of the interpolation area. So leave the default value and press Enter.
The last query is:

SMOOTHING [ 16]:

This value (specifying how many times smoothing has to be performed) are estimated by SURGEF so that the resulting surface will be smooth enough.
Press Enter to accept the default value.
The program SURGEF computes the surface showing the iteration process of interpolation, tensioning and smoothing. The process can be stopped by Esc key - in this case the actual iteration step is completed before the stop. If the computation is finished, the created surface is stored in the binary file EX1F.GRA (as values of matrix elements) and you can press Enter to finish SURGEF.

How to display a created surface

As soon as the file EX1F.GRA exists, you can use functions for displaying the surface. The shortcut key C is used for displaying the raster color map. Shadowed relief display (key Alt+Q) improves 3D feel of raster color map. The key Alt+S displays the color scale with corresponding levels. To restore the original display (only points in this case), press the key R.

How to calculate and display isolines

Before displaying, isolines must first be calculated. Select the menu item Interpolation / Calculate isolines. The following dialog appears:

In this dialog you can set levels of the first and the last isoline, the interval between isolines and divisor (isolines with level divisible by divisor will be labelled). Then press the button OK. The calculated isolines are stored in the file  NAME.VRs, where  s  is a suffix (see [3]) and they are immediately displayed. If you select a too small difference between isolines, calculation can last several seconds. If the surface is later created with different interpolation / approximation parameters, you should recalculate isolines to correspond to the actual surface.
Isolines stored in the file  NAME.VRs  can be displayed by the shortcut key I.

How to display 3D view of surface

In the main menu select item Display / 3D view. The following dialog appears:

If the grid has too big size (for example more than 500 in the x-direction), the 3D display will be to too dense and maybe too slow. You can specify step of reading grid file (in our case the grid file is EX1F.GRA) greater than 1 to decrease size of displayed grid. As soon as the button OK is pressed, 3D view of the surface is displayed. SurGe switches into special mode with its own menu. Each item of menu corresponds to certain shortcut key - try all of them to rotate 3D view, to increase / decrease z-scale and so on (details are in the chapter 3D display the User's Manual). To return into move/zoom map mode, press Esc key.

Chapter 2: Interpolation / approximation parameters

How to change interpolation / approximation parameters

Quality of surface generated by the program SURGEF can be changed in dialog box invoked in main menu by Interpolation / Interpolation parameters:

The first parameter (Filter) is intended for reduction of input points, if number of points is very large and if there are points with small horizontal distance between them. Usage of the parameter Filter is explained in the next section of this chapter (see How to filter input data).

Parameter Smoothness enables to control smoothness of generated surface. The larger value, the sharper interpolation is obtained. Typical values are:
0.00 - 0.30 ... for smooth interpolation
0.40 - 0.60 ... for normal interpolation (default value is 0.50)
0.70 - 1.50 ... for sharp interpolation

Sharp / smooth model at local extremes can be improved by extending of the smoothing parameter. Beginning from the version 5.50, the smoothing parameter can have two formats:
  1) number 0.00 - 9.99, which is equivalent to the above described smoothing parameter
  2) number 100.00 - 999.99, where the first two digits divided by 10 determine so called shape factor, which has influence on the shape of surface in the surrounding of sharp local extremes. The smallest value 1.0 means, the shape will not be changed and any greater value (1.1-9.9) means, the local extreme will be sharper. The remaining digits have the original meaning.
Remark: If the smoothing parameter has the first format, the shape factor has the default value 1.0.

Parameter Accuracy specifies, how accurate the generated surface has to be. It represents the percentage value from  Z_max-Z_min, where  Z_min is the minimal value and  Z_max  is the maximal value of all z-coordinates. If maximal difference between z-coordinates of points XYZ and generated surface is less than  Accuracy·(Z_max-Z_min)/100, the process of  interpolation / approximation is finished.

In fact, the parameter Enlargement is not a parameter affecting interpolation / approximation method. The value specifies number of grid rows and columns, which has to overlap interpolation area. By this way, the shape of  the surface near to the grid boundary will be improved. The value of parameter Enlargement should be approximately set to (i1+j1)/10 (where i1 and j1 are dimensions of grid). If it is greater than 98, the program SURGEF computes it internally.

The parameter Linear tensioning enables to set the degree of linear tensioning. It can have four values:
0 ... no linear tensioning
1 ... medium linear tensioning
3 ... strong linear tensioning
4 ... full linear tensioning

In most cases the number of iterations can be decreased by the transformation  P_new = A·P_old + B, where  P  is smoothed matrix (see User's Manual) and constants  A  and  B  minimize the term  å(A·f(X_i,Y_i)+ B - Z_i)². The resulting surface is somewhat smoother, but the number of iterations is decreased by cca 30%. The check button Faster convergence enables this feature.

Pre-defined parameters contains list of interpolation / approximation modes and enables to set appropriate parameters for selected mode. The modes and pre-defined parameters are:

Mode	Filter	Smoothness	Accuracy	Linear tensioning
Trend Surface	30	0.1	90	0
Smooth approximation	200	0.2	20	0
Smooth interpolation	500	0.2	1	1
Normal interpolation	500	0.5	1	1
Sharp interpolation	500	200.7	1	1
LES interpolation	1000	-0.5	1	1
Digital model of terrain	1000	200.7	1	3

Important note: The Trend surface and Smooth approximation set special multiplier for SMOOTHING parameter estimated by SURGEF. To deactivate this setting, select Normal interpolation.

How to obtain sharp interpolation

To demonstrate sharp interpolation we will use the file EX1.DTA (select the subproject Example 1 in the SurGe Project Manager and The first example map). In the main menu select item Interpolation / Interpolation parameters. Set the parameter Smoothness to 200.7 and the parameter Accuracy to value 0. Start SURGEF (see [2]) and answer according to the following table:

In 3D view you can see, the resulting surface is sharp in comparison with normal interpolation performed in chapter "Basic operations".

How to obtain smooth interpolation

To demonstrate smooth interpolation we will use the file EX1.DTA (select the subproject Example 1 in the SurGe Project Manager and The first example map). In main menu select select item Interpolation / Interpolation parameters. Set the parameter Smoothness to 0.2 and the parameter Accuracy to value 0. Start SURGEF (see [2]) and answer according to the following table:

In 3D view you can see, the resulting surface is smooth in comparison with normal interpolation performed in chapter "Basic operations".

How to obtain smooth approximation

To demonstrate smooth approximation we will use the file EX1.DTA (select the subproject Example 1 in the SurGe Project Manager and The first example map). In main menu select select item Interpolation / Interpolation parameters. Set the parameter Smoothness to 0.0, the parameter Accuracy to value 40 and switch Faster convergence on. Start SURGEF (see [2]) and answer according to the following table:

In 3D view you can see, the resulting surface is very smooth (in comparison with normal interpolation performed in chapter "Basic operations") and it does not pass through the points exactly.

How to obtain trend surface

Trend surface can be obtained as a very smooth approximation. It is convenient to select a small grid size (and later to double it once or more times, if it is needed), because smoothing of large grids is not effective enough. Small grid size can be set directly in SURGEF (as an answer to the GRID SIZE IN X-DIRECTION) or via low Filter value. It is also essential to set high precision (a safe value is 90) to avoid iterations and to select a greater number of SMOOTHING cycles.
For demonstration purposes we will use the file EX5.DTA (select the subproject Example 5 in the SurGe Project Manager). The easiest way, how to set appropriate parameters, is to select Trend surface in the list of pre-defined parameters (see the dialog box Interpolation parameters under the Interpolation menu). Now we can run SURGEF and leave default values:

As you can see, the SMOOTHING parameter is very high -  the appropriate value should be 5-10 times higher than the grid size. If you want a more even surface, decrease the grid size and increase SMOOTHING. Try, for example, to set grid size to 60 and SMOOTHING to 5000.
Important note: The Trend surface and Smooth approximation in the dialog box Interpolation parameters sets a special multiplier for the SMOOTHING parameter estimated by SURGEF - that is why it is so high. To deactivate this setting, select Normal interpolation; otherwise smoothing will last a long time, if the grid size is great.

How to utilize trend surface for improving extrapolation

Trend surfaces (see the previous section) can be used as a base for normal interpolation. Because the process needs several steps and settings, it is automated as described in the section Interpolation with trend surface in the User's Manual.
For demonstration we will use the same data file as in the previous section - select the subproject Example 5 in the SurGe Project Manager, run SurGe and in the Interpolation / Interpolation parameters / Pre-defined parameters select Normal interpolation.
In the first step select Interpolation / Data analysis (see the section Data analysis in the User's Manual) to fix Target grid size. In our example we can leave the default values.
In the second step select Interpolation / Interpolation with trend surface and leave 1 in the following dialog box Preservation of extrapolation trend. Now SurGe runs SURGEF twice (do not be surprised). In the next picture you can see the resulting surface (on the right side) in comparison with the surface obtained by normal interpolation (on the left side). It is obvious, former has better grading in areas without points.
Try the same with Preservation of extrapolation trend 2 and 3.

How to interpolate terrain data

If the input data represents measurement from some terrain, it is suitable to use "strong" linear tensioning with a small number of smoothing (which is close to the Triangulation with Linear Interpolation method). As a rule, characteristic points of terrain are measured - this means that the person performing such a measurement surveys only points where the slope of terrain changes (tops, edges, valleys and so on). For interpretation of such data, the Triangulation with Linear Interpolation method is usually used, so the ABOS method is applicable as well.
To demonstrate this feature we will use the file EX3.DTA (select the subproject Example 3 in the SurGe Project Manager). In main menu select item Interpolation / Interpolation parameters. Set the parameter Smoothness to 0.2, Linear tensioning to 3 and switch Faster convergence on. Start SURGEF (see [2]) and answer according to the following table:

How to filter input data

There is possibility to filter input data (points XYZ) using parameter Filter. Value of this parameter should be in the interval <3,9999>  and has the following meaning: If the horizontal distance between two points [X_i,Y_i,Z_i] and [X_j,Y_j,Z_j] is greater than max{(x2-x1),(y2-y1)}/Filter, these two points are replaced by one point [X_k,Y_k,Z_k] with average coordinates  X_k=(X_i+X_j)/2, Y_k=(Y_i+Y_j)/2  and  Z_k=(Z_i+Z_j)/2.  If it occurs, the resulting surface will be generally approximative. Default value of filter is 500. Special value 0 means that only the points having the same x and y coordinates will be filtered. The filter pre-processes the resolution of resulting map, which is similar to the resolution of a digital picture - if the distance of two points with different colors is smaller than the pixel size of the digital picture, you can see only one point with "average" color.

To demonstrate effect of the parameter Filter, we will use example EX4.DTA (select the subproject Example 4 in the SurGe Project Manager), which contains 7000 points.

Now you can experiment with parameter Filter. In the first step set the Filter to value 100 and perform interpolation. Start SURGEF (see [2]) and answer according to the following table:

As you can see (for example in raster color map display - press shortcut key C), the resulting surface is too "noisy":

Now set the Filter to 30, again start SURGEF and answer according to the following table:

You can see, the "noise" is significantly reduced:

Even better filtering effect can be obtained, if the parameter Accuracy is set to some higher value (10 - 30). Try it.

How to use different modes of interpolation

A click on mouse right button displays a local menu, which enables to perform several types of interpolation:

In addition to the Normal interpolation mode, SurGe offers several other modes suitable for special purposes:

Linear mode is a little bit faster than normal mode. This mode is favourable for zero based maps and digital model of terrain (especially if it is used with linear tensioning 3). The disadvantage is worse extrapolation outside convex envelope of points XYZ.
Convex mode uses balanced combination of normal and linear tensioning. It is faster than normal mode - in case of great number of data and large grid, this mode can be 4-5 times faster than normal mode, especially if used for preview (smoothing is zero). The disadvantage is worse extrapolation outside convex envelope of points XYZ.
Per partes constant mode performs only per partes constant interpolation.

Normal, Linear, Convex and Per partes constant modes can be combined with the following modes:

Auto mode runs SURGEF.EXE without waiting for user response.
Preview mode performs very fast interpolation without smoothing and without waiting for user response.

Chapter 3: Digitization

Up to now we have been using the program SurGe in move/zoom mode. If you press Enter, the program switches into digitization mode (press Esc to return back to move/zoom mode). In this mode, the cursor changes to little cross and cursor keys have another function - they move cursor around the screen (shortcut keys 1, 2, 3,  and 4 change step of movement). If you press Ctrl key and a cursor key, you still can move map as in move/zoom mode. In the program bar you can see x, y and z (if the surface was created) coordinates of the cursor position. Information about actual mode is displayed in the status bar.
The digitization mode has different main menu. The first item (Object) contains objects, which have to be digitized. For example, if you want to digitize a boundary, select Object / Boundary.
The digitization of any object can be also selected by menu item Digitization in move/zoom mode (for example Digitization / Boundary).

Important: If you want to save changed objects, you must select menu item Object / Save or you must return to move/zoom mode and select menu item Digitization / Save objects.

How to digitize points

In the digitization mode there are three functions for editing points XYZ. You can add point, delete point or change z-coordinate of point.
To demonstrate this feature, select the subproject Example 2 in the SurGe Project Manager and press Run SurGe. This example contains not only points XYZ, but also the boundary (thick red line), the spatial polyline (dot orange line) and the faults (green lines).
Switch to digitization mode (press Enter, if you are in move/zoom mode) and select points as digitized object (choose Object / Points in the main menu). Let us suppose, you want to delete point with label LB03 (if you want to highlight the label, press Alt+W and enter "LB03"). Locate cross cursor so that the point is the nearest point to the cursor. Press Ctrl+B or click right mouse button - you can see, the point disappears.
Now let us suppose, you want to add new point. Locate cross cursor so that it has approximately coordinates X=250 and Y=300 (check the program bar, where the coordinates are displayed). Press B or click left mouse button. In the provided dialog box enter z-coordinate of the new point and press Enter. A new point has always label starting with ## and it is considered to be so called added point. Added points are stored (when you select menu item Object / Save) in separate file with extension DBs.  
If you want to change z-coordinate of a point, again locate cross cursor so that the point is the nearest point to the cursor and press Shift+B. In provided dialog box enter new z-coordinate of the point.

How to digitize boundary

There can be up to 100 boundaries in the program SurGe, each defined as a polyline. In the digitization mode you can start to create a new boundary, add a new segment, delete last segment or to move selected point.
We will use the same data as in the previous section. Switch to digitization mode (press Enter, if you are in move/zoom mode) and select digitized object boundary (choose Object / Boundaries in main menu).
To create new boundary, press Ctrl+H (or click right mouse button). Than you can locate cross cursor at desired position of the first boundary point of new boundary and press H (or click left mouse button). Do the same for second boundary point. If the first two points have different location, you can see the first segment of new boundary (thick red line). By this way you can continue and so create desired boundary. The last boundary segment can be deleted using shortcut key D. If you want to close the boundary, press key U.
A point of existing boundary can be moved - locate the cursor near to selected point of boundary and press Shift+H (the point will have light blue color). Then locate cursor to new position and press M.
Item Make boundary as a convex envelope under menu Boundaries creates a new boundary as a convex envelope (convex hull) of points XYZ. The number entered in the following dialog box enables to scale the convex envelope. Using this feature you can change the size of interpolation area and to remove grid values outside of the convex envelope. 

How to digitize spatial polylines

Spatial polylines are used in the program SurGe as an expletive mean for definition of the surface. There can be up to 300 spatial polylines containing up to 10000 points. Each endpoint of the polyline segment can have undefined value (1E29) or defined value (less than 1E29). There must be at least two defined values for each polyline - the remaining values are computed as soon as the digitization mode is finished. Spatial polylines are displayed as orange dot lines.
Let us again use the file EX2.DTA. Switch to digitization mode (press Enter, if you are in move/zoom mode) and select digitized object polylines (choose Object / Polylines in main menu).
To create a new polyline, press Ctrl+L (or click right mouse button). Than you can locate cross cursor at desired position of the first point of new polyline and press L (or click left mouse button). In the provided dialog box enter z-coordinate of the point. Do the same for second polyline point. If the first two points have different location, you can see the first segment of new polyline (dot orange line). By this way you can continue and so create desired polyline. The last polyline segment can be deleted using shortcut key D. If you want to close the polyline, press key U.
A point position of existing polyline can be moved - locate the cursor near to selected point of polyline and press Shift+L (the point will have light blue color). Then locate the cursor to new position and press M.
Sometimes it is desired to define polyline with constant z-values at its points. In this case press key F and in the displayed dialog box enter the constant value. Then, if you press L to define new point of the polyline, the constant is assigned to z-coordinate of the point automatically. This feature can be switched of by shortcut key Ctrl+F.
If a polyline is created, it is necessary to set its number of internal points. In fact, SURGEF does not work with polylines directly - it works only with the points, which are evenly distributed along the polyline. To specify the number of these points, locate the cross cursor near to the polyline and press P. Then in the provided dialog box enter the number of internal points (typical values are 50 - 200).

How to digitize faults

Menu item Faults enables to edit sequences of line segments (in horizontal plain), at which the resulting surface has to be discontinuous. Each fault is defined by pair of points and is displayed in green color. Choose Object / Faults in the main menu. To define a new end point of fault, locate cursor at desired position and press key Z. The fault can be deleted using key D - that one, which center is next to the cursor position. The position of fault endpoint can be changed by key Shift+Z. Maximal number of faults is 1000.

How to create and display cross-sections

In the digitization mode you can specify a cross-section and display it. It is possible to create the cross-section through up to 9 surfaces (layers). To demonstrate cross-section mode, we will use files EX1.DTA, EX1.DTB, EX1.DTC  and  EX1.DTD (select the Example 1 in the Surge Project Manager). These files contain the same set of the points, but with different z-coordinates.
In the first step you must create surfaces for all these files (see Chapter 1: Basic operations). Remember, you must specify the same grid dimensions for all surfaces.
In the second step switch to digitization mode (press Enter, if you are in move/zoom mode) and select digitized object cross-section (choose Object / Cross-section in main menu). The first or next point of cross-section can be specified using key G (or click left mouse button). Points are displayed by red color. Polyline connecting red points is displayed using key E. All specified cross-section points can be deleted by key Ctrl+G and then new cross-section can be defined.
Try to create cross-section through points LB28, LB07, LB10, LB14 and LB06. Then press Enter and fill items in the following dialog box like this:  

In the first column enter the suffix of layer, in the second column brief description of layer and press Enter - the program switches into cross-section mode. The cross-section is constructed through all specified surfaces and displayed in a 2D plot. There is a special menu in the cross-section mode. Title of the plot and description of axes can be modified using menu items Graph title (key N), Description of x axis (key X) and Description of y axis (key Y). The range of y axis can be changed by item Change range of y axis (key Ctrl+Y). Menu item Save cross-section (key U) enables to save the position of cross-section polyline into file  NAME.RZY  for later using in the digitization mode. Name of the cross-section must be specified as a single character A-I.
If there is a saved cross-section, you can display it in the digitization mode using key Shift+G. If you press this key, the following dialog box appears:

In this example, six cross-sections were saved and the cross-section D was selected. You can enter any combination of letters stated in dialog bar without delimiters (for example ADC). As soon as you press button OK, positions of these cross-sections are displayed by thick lines in red color. If you select only one cross-section, you can then press Enter and directly switch to the cross-section mode.

How to measure horizontal distance

As soon as the second point of the cross-section is specified, you can see in the program bar the distance measured along the cross-section polyline (the last item after D=). To display cross-section polyline use the key E. To delete specified cross-section points and to reset the distance to zero use key Ctrl+G.

How to digitize isolines

In the digitization mode there is also possibility to modify isolines. The first function,  Mark isoline  (key X), serves for selection of a isoline. After selection, the isoline is represented by sequence of white points. If the display is (due to operations) damaged, it can be restored by menu item  Redraw modified isoline  (key A). Selected isoline can be smoothed (Smooth isoline, key S) as a whole, or partially (Smooth between points, key V) between the points selected using menu items  Mark first point  (key Alt+1)  and  Mark second point  (key Alt+2). There is also possibility to mark single point of isoline  (Mark point, key Shift+I) and move it (Move point, key M). Certain number (the number can be changed by  Change number n, key Ctrl+Q) of isoline points can be moved by  Move n points  (key Q). Modified isoline can be saved into file  NAME.VRz using menu item  Save modified isoline  (key Ctrl+I).  Write marked isoline  (key W) enables to store selected isoline as ASCII file IZ.$$$.

How to digitize background

In some cases it is useful to display texts and some characteristic terrain lines and / or objects to improve orientation in the map. For this purpose, there is a special digitization level named  Background  under menu  Digitization. Objects of background are handled as polylines and there are the following functions for creating, changing or deleting objects of background:

Start new object   (Ctrl+B)	ends construction of the current object and starts construction of a new one
New point of object  (B)	a new point of object polyline is specified at cursor position
Delete last point  (D)	the last specified point is deleted
Close polygon  (U)	the next point will be at the same position as the first point of the polyline
Mark point  (Shift+B)	mark the nearest point of the polyline by white color
Move point  (M)	move marked point to a new position
New text (T)	specify text string, font size, font thickness, font color and text orientation
Change text (Shift T)	change text string, font size, font thickness, font color and text orientation

Three functions are intended for manipulation with whole objects:

Select object/text (S)	select / unselect the object next to the cursor. Selected object is displayed by violet color
Move selected object/text  (Ctrl+M)	move whole object; moving vector is given by marked point and the cursor position
Delete selected object/text  (Ctrl+D)	delete selected object

All background objects can be saved into file  NAME.BG  by the last menu item  Save background  (key W).

You can use keys for moving map (Ctrl and arrow keys, PgUp, PgDn) and keys for display of point labels, z-coordinates, isolines, raster color map and so on. (see [4]).

Chapter 4: Grids

How to create ASCII grid

To ensure compatibility with other mapping packages, SurGe can export grid in ASCII format compatible with Surfer (Golden Software). Most of mapping packages can import grids in this format. If you have created a grid and if you want to save it as an ASCII file, select the menu item Output / ASCII File. The ASCII file NAME.GRs will be saved in your working directory.
Let us suppose, you have created grid from input data EX1.DTA. Select the menu item Output / ASCII File - in your working directory you can see new ASCII file EX1.GRA.

How to import other map/GIS grid formats

SurGe and SurView utilize the GRIDCONV.EXE command line utility (see Conversion command line utilities) for importing some common map/GIS grid formats - DEM, Surfer ASCII, ArcGis and GRASS. If a file containing one of these grids is entered as a parameter (without a suffix), SurGe or SurView tries to recognize the format and calls GRIDCONV.EXE to create a native SurGe grid. In the case of SurGe, the basic data file is also created. DEM files are recognized according to the file extension DEM, other formats are recognized according to the first lines of the file.

The following command line statements are examples of how to import grid files:

SurGe baraboo.dem
SurGe calls GRIDCONV to read the BARABOO.DEM file and creates BARABOOF.GRa and BARABOO.DTa files.

SurView MNT450.ASC 
SurView calls GRIDCONV to read the MNT450.ASC ArcGis file and creates the MNT450F.GRa file, which is immediately displayed.

This picture shows an ArcGis grid displayed by SurView.

How to utilize existing grid

In some cases it is suitable to work with existing grid, which can result from another evaluation - for example from evaluation of seismic data. Let us name such grid as an external grid. SurGe can import external grids, if they are stored in ASCII format compatible with DEM (USGS Digital Elevation Model), Surfer (Golden Software), ArcGis and GRASS. Most of mapping packages can export grids in this format.
If you want to import an external Surfer ASCII grid, rename it according to the name conventions (see [3]). For example, if your file containing basic data has name SEISM.DT9, rename the external grid file to SEISM.GR9. 

In the next example we will use the grid EX1.GRA created in the previous section. To prevent SurGe from automatic reading of binary grid file, delete file EX1F.GRA (it is not necessary - do it only for demonstration purposes).

Let us suppose, the grid EX1.GRA created in the previous section is such external grid. Read input data EX1.DTA as described in [1]. Select the menu item File / Read grid from ASCII file. The external grid is read, transformed into binary format and immediately written as binary file EXIF.GRA (check now your working directory). Moreover, you can work with grid as if it was created by interpolation process.

Let us suppose, you have grid, which is approximative (the surface does not pass through the points  XYZ  exactly), but you want more precise surface. In such case proceed according to the following steps.

1. Read input data.
2. Start interpolation using the menu item Interpolation / Calculate grid.
3. Answer Y to the prompt of SURGEF:

   READ FILE .GRD? (Y/N) [N]

4. Now, SURGEF will read existing grid. If you want to smooth this grid, enter positive number as an answer to the next prompt:

   SMOOTHING OF READ GRID [  0]

5. Answer to the remaining prompts as usually.

SURGEF will perform steps 4. through 9. (see User's manual) of interpolating algorithm.
By this way you can achieve precise interpolation while the surface is corrected only in surroundings of the points  XYZ, through which original surface did not pass exactly.

How to directly convert seismic reflection times to structure depth

The processing of seismic data is one of the most significant tasks for geologists if they have to create a geological map of some underground rock structure. The typical results of seismic measurement are times at which reflected sound waves return from a certain boundary between different types of rock. These times are, of course, measured from some datum level and they are usually recorded using a dense mesh covering the area of interest with a typical number of nodes between 10000 and 100000.
Because the homogeneity of covering rocks cannot be assumed and the speed of sound waves in covering rocks is unknown or known only approximately, the measurement must be supported by precise depth values usually measured at exploration wells. In general, the interpreter has to work with two sets of data - the first one is the dense mesh of reflection times and the second one is the measurement of rock structure depth at wells. Let us note that the number of wells is usually small in comparison to the number of points at which the reflection time is measured.
To demonstrate the interpretation of seismic measurement we will use the data set SEISM1.DTc containing reflection times - the corresponding grid is shown in the next figure.

The file SEISM1.DTc contains reflection times in the range from 1736 to 1875 seconds at 25853 points. It is obvious that the lower the value of reflection time, the higher the position of the rock structure boundary.

The depth of the rock structure was also measured at 14 wells and the results were stored in the file containing the second data set SEISM1.DTa - see the next list of the file content.

1225.976 2339.511 -2246 W-01
 837.871 2270.595 -2250 W-02
 428.004 2118.255 -2271 W-03
 859.634 1878.863 -2272 W-04
 181.357 1519.776 -2292 W-05
1940.525 2187.171 -2277 W-06
2738.498 2292.358 -2255 W-07
2981.517 2375.783 -2238 W-08
3344.232  935.805 -2338 W-09
2121.882  812.481 -2317 W-10
 493.292  500.547 -2309 W-11
1519.776 1733.777 -2267 W-12
3663.421 2143.645 -2264 W-13
2999.652 2172.662 -2252 W-14

As follows from the list, the range of depths is -2338 to -2238 meters. As a rule, the depth of geological structure is a negative value measured from some datum plane (for example sea-level).

The standard procedure of seismic data processing is the following:
1. The map of reflection times is created.
2. For all wells the sound speed is calculated from known structure depth and reflection time at the well.
3. The velocities known at well positions are used for creation of the so-called velocity map.
4. The velocity map is multiplied by the map of reflection times and thus the map of depths is obtained.

The SURGEF offers another solution: to create map of depth directly from the structure depths at wells using the reflection time grid as an external grid. It means that the grid containing the map of reflection times SEISM1f.GRc is copied (renamed) into the file SEISM1f.GRa and this grid is read at the beginning of the interpolation process. It may seem to be strange especially if we realize that the reflection times are positive values while the structure depths are negative. Let us have a closer look at the procedures performed by SURGEF.

Firstly, the SURGEF is run for the data set SEISM1.DTa and it is instructed to read the external grid SEISM1f.GRa (which is the copy of SEISM1f.GRc and represents the map of reflection times) by answering Y to the prompt:

READ FILE .GRD? (Y/N) [N] Y

Then SURGEF changes this grid using the linear transformation P_new = A·P_old + B, where the constants A and B minimize the term  å(A·f(X_i,Y_i)+ B - Z_i)², as described in section Smoothing in the SurGe User's Manual.

In this case the constant A was computed as the negative number -1.160139 and together with B (-217.38) changed the grid so that the sum of squared differences between the new surface and structure depths at wells is minimal. As expected there were some differences between the new surface and the structural depths at wells because of heterogeneity of covering rocks; however these differences were used in the next iteration cycle (cycles) as in the normal interpolation process.

As a result, the new surface passes through negative z-coordinates of structural depths while conserving the morphology corresponding to the reflection times.

How combine interpolation and approximation

Another example, how to utilize existing grid, is a combination of interpolation and approximation:
Suppose, that you have a set of points in the file COMB.DTA and you need to create a surface, which is approximative, but it goes exactly through some selected points. In this case the following procedure is recommended:
1) Rename the file containing your data to COMB.DBA.
2) Create a new basic data file COMB.DTA and copy into it the points, through which the surface has to pass exactly.
3) Start SurGe and select only Added points in Interpolation / Objects for interpolation.
4) Select Smooth approximation in Interpolation / Interpolation parameters and Calculate grid.
5) Select only Points in Interpolation / Objects for interpolation.
6) Select Normal approximation in Interpolation / Interpolation parameters and set Accuracy to 0.
7) Calculate grid and do not forget to answer Y to the SURGEF prompt "READ FILE .GRD?".

How to modify the size and the shape of the grid area

If there is no boundary in input data, the size of grid area is given by minimal and maximal coordinates of  XYZ points. This size can be changed by a boundary - if a boundary exists and if it is involved into interpolation (see the dialog box Interpolation / Objects for interpolation), the size of grid area is given by minimal and maximal coordinates of boundary points.
To demonstrate this feature we will use the file EX3.DTA containing terrain data (select the subproject Example 3 in the SurGe Project Manager). Switch to the digitization mode (press Enter, if you are in the move/zoom mode). You can create a boundary "by hand" (see the section How to digitize a boundary), but try to use the menu item Boundaries / Make boundary as a convex envelope. By this way you will create the boundary automatically and you can scale it by scaling factor entered in the provided dialog box (select 1.1 to enlarge the grid area by 10%). Now return to the move/zoom mode (press Esc, if you are in the digitization mode) and perform the interpolation as described in the chapter How to interpolate terrain data.
The boundary can change not only the size of the grid area, but also its shape - select Interpolation / Blank grid outside boundary to remove grid values outside the boundary (enlarged convex envelope in our case). You should obtain the result like this:

How to perform mathematical calculations with grids

There is a possibility to perform certain mathematical calculations with grids. Let us suppose, you have created grids for examples EX1.DTA and EX1.DTB representing top and bottom of a layer and you want to create a grid representing the thickness of the layer. It means, you need the grid for which value at each node is equal to value of the first grid minus value of the second grid. Proceed according to the following steps:
1. Read input data EX1.DTA as described in [1].
2. In the menu Interpolation select menu item Math calculation with grids. You will see this dialog box:

The actual surface (in our case the surface corresponding to the suffix A) will be used as the first operand of the calculation. The second surface (in our case corresponding to suffix B) will be the second operand, so enter B (or b) in the first edit field. In the middle edit field you have to enter operation - in our case character - (minus). The last field has contain a suffix of result surface. Be sure, you do not enter the suffix of existing surface - otherwise, it will be replaced without prompt (if you are not sure press Cancel button and check your working directory). Type, for example, Z (or z) and press OK button. At this moment, the new surface with extension Z is created and stored (as a file EX1F.DTZ) in working directory.
Z-coordinates of all points and spatial polylines are re-calculated so that they correspond to the new surface. If you want to save them, select the menu item Digitization / Save objects.
Meaning of other operations is explained in User's manual.

How to simulate wedging out of layers

Construction of a layer geometry is one of the basic tasks in reservoir engineering. The boundaries between individual layers are constructed as surfaces passing through structural depths (z-coordinates) measured in wells. As explained in the section How to directly convert seismic reflection times to structure depth, layer construction may be combined with seismic measurement, if it is available.
If there is a small layer thickness indicated in some wells, no algorithm for smooth interpolation can ensure that the bottom layer boundary will not exceed the top layer boundary. The next two figures illustrate such situation - in the first figure there is a top layer boundary (contained in the file GRES.DTa) and the bottom layer boundary (contained in the file GRES.DTb) of a gas reservoir structure including the position of the cross-section A-A', where the bottom layer boundary exceeds the top one (see the second figure). Such a phenomenon suggests that a so-called wedging out of layer (which is common in geology) should be interpreted.

This problem can be effectively solved in the SurGe graphical interface using mathematical operations offered in the dialog Math calculation with grids, where selected binary mathematical operation is performed for all z-values at nodes of grids representing the two surfaces.
There are two mathematical operations represented by characters $ and %, which can be utilized for solving the wedging out of layer problem. In the case of the first operation ($) the resulting value is the z-value of the first surface, but if the z-value of the second surface is greater, the resulting value is the average. In the case of the second operation (%) the resulting value is the z-value of the second surface, but if the z-value of the second surface is greater than the z-value of the first surface, the resulting value is the average.
Both mentioned operations were applied for the presented surfaces and the resulting new surfaces were stored with new suffices 1 and 2. The following figure contains the cross-section A-A' through the new surfaces indicating that the wedging out of layer problem was properly solved.

Maps of thickness and volume calculation

This example is concerned with the estimate of the new snow volume in avalanche field after an avalanche event. Two data sets were available for solving this problem - AVALAN.DT0 containing the measurement of snow surface before the avalanche event and AVALAN.DT1 containing the measurement of snow surface after the avalanche event.

On the next figure there are two maps of snow surface created from the above-mentioned files corresponding to the situation before and after the avalanche event; the white line determines supposed boundary of the avalanche field.

There are no visible differences between both surfaces, but as soon as the first surface is subtracted from the second (using the menu item Interpolation / Math calculation with grids), the map of the new snow thickness is obtained (see the next figure).

It is obvious that snow increased also outside the supposed boundary of avalanche field - it was probably caused by the additional snowing, by creation of snow drifts and so on.
To calculate the volume of new snow layer, the VOLUME utility (see Calculation of volumes) can be used:

From this figure the following results are obtained:
The volume of the new snow layer in the avalanche field is 484424 m3, the horizontal area of avalanche field determined by the boundary is 293144 m2 and the maximal thickness of new snow layer is 3.73 m.

Chapter 5: Print

How to print map

A map can be printed in using the menu item File / Print. The following dialog box will appear:

Here you can select a printer installed on your system, paper size and / or paper orientation. If you press OK button, you will see the dialog box like this:

The first line contains page sizes (in cm), as they were detected for the selected printer. The second line contains range of x values (x2-x1) and range of y values (y2-y1).
In the third line SurGe suggests size of printed map. The size is suggested so that map will fit into page. You can change these values. If you enter less values, you will obtain a smaller map. If you enter greater values, you will obtain larger map - in this case the map could exceed the page margins.
To shift the map beginning, set X start and Y start values. The greater value of X start will move map to the right, the greater value of Y start will move map to the up. You can also use a negative value(s) to move map to the left (down).
If you want to print axes, check button Print axes.

A printed map will contain all objects displayed on the screen - for example, if point labels and map mesh are displayed on the screen, they will be printed.

How to print isolines

In the dialog for isolines calculation (see  [5]) you can set levels of the first and the last isoline, the step between isolines and the divisor. Remember, only isolines with level divisible by the divisor will be labelled. As a rule, if isolines are displayed on the screen, they will be printed. Labeled isolines are drawn by thick lines, while other isolines are drawn by thin lines - see the next picture with a detail of printed output.

In this picture the step between isolines is 1 and the divisor is 5.

How to print cross-section

The construction of a cross-section is described in the User's manual (see [6]). In the cross-section mode there is the menu item Cross-section / Print, which enables to print displayed cross-section on selected printer. As in the case of map printing (see [7]), you can select in the first dialog box a printer installed on your system, paper size and / or paper orientation. The meaning of items in the second dialog is the same (see [8]), but check button Print axes is missing (axes are always printed in the print of cross-section). The title and axes description can be changed by shortcut keys N, X and Y. The next picture shows an example of printed cross-section through two surfaces.

How to create PostScript print

It is sometimes suitable to create printed output in PostScript or PDF format. In Windows environment it is not difficult. The only thing, which has to be done, is installation of a PostScript printer. If you want to have PostScript print, follow these steps:

In the Start menu select Settings / Printers and Faxes. In the presented dialog box select File / Add Printer. Press the Next button and in the next dialog choose Local printer. Again press the Next button and in the following dialog once again. You should see the dialog box Select a Printer Port. Choose FILE (Print to File) and again press the Next button. In the following dialog select a PostScript printer (I recommend HP Color LaserJet 8500 PS). The remaining answers of printer installation are up to you.

Now you can create PostScript print from any application, which can print to a Windows printer. If you select your PostScript printer before printing, you will be asked for a file name. Remember to use the file extension .PS (standard extension for PostScript files).

PostScript files can be viewed by GSview, which is available from:

http://www.cs.wisc.edu/~ghost

GSview requires Ghostscript, which must be downloaded separately. GSview enables to create a PDF file - just select File / Convert and pdfwrite.