Data Modeling

Data modeling is taking information and looking at it in different ways. A report is a form of data modeling, because it is a representation of data that can take on various output styles. Data modeling extrapolates data, meaning that in addition to displaying the data, it makes an “interpretation” of some kind.

One form of modeling is taking your data points and creating contoured surfaces. If you have a series of discrete points on your site, you can compile the data and try to read the patterns in between the data points. gINT has some basic modeling capabilities which we will review later, but it is not a modeling program. However, it can interface with programs that are.

Note: This exercise requires the use of projects, library and other files available from: download.aspx.  Instructions for unzipping and setting up these files is on: using gint downloaded examples.aspx.

Contouring Data Using gINT and Surfer® 

Note: For more information on Surfer products, you can view Golden Software’s Web site at http://www.goldensoftware.com/.

1. Go to INPUT.

2. Open surfaces.gpj (typically located in \gINT\projects\).

3. Select Additional Modules->Surfaces Support. This places a Surfaces tab in your project database.

   Note: If the Surfaces tab is already present, select Additional Modules->Surfaces Support twice to remove the tab then bring it back. This clears any pre-existing data.

   In any database of subsurface information you have X, Y and Z information. X and Y are the borehole coordinates, and Z is a parameter. We are going to model two parameters: ground surface and top of bedrock.

4. Select File->Import/Export->Export Contouring Data. You see the Export Contouring Data dialog box:

    

5. Enter the following values in the Main tab:

   Field Name	Value	Comments
   Export to File	Ground Surface.csv	Click the Browse button and specify a CSV file type, file name and location, then click Save.
   Field containing Z values	[POINT].[Elevation]
   Z Values are	Elevation

   The program assumes that the X and Y values are the native North and East coordinates in the project database. The Field Containing Bearing field is only applicable if you have inclined holes.

6. Click the Browse  button on the Select Points field to select the boreholes you want to export. For our purposes, leave the field blank to export all the boreholes.

7. Click OK when you are finished. The program tells you how many records were exported. Notice that the file is exported to your Projects folder.

   

8. Click OK to close the dialog box. The .CSV file has been generated.

9. Open Ground Surface.csv in Excel. It appears as shown:

    

10. Notice that the first two columns hold East and North values, respectively. The third column holds Elevation values, and the fourth column holds the Borehole ID numbers.

We will export another CSV file, this time for top of bedrock values.

1. Select File->Import/Export->Export Contouring Data.

2. Select the following values in the Main tab of the Export Contouring Data dialog box:

   Field Name	Value
   Export to File	Bedrock Surface.csv
   Field containing Z values	[LITHOLOGY].[Depth]
   Z Values are	Depth, convert to elevation

3. When you are finished, your screen should look similar to the following:

   

   Notice that we are exporting LITHOLOGY records, as opposed to POINT records (exported in the previous export operation). We will need to filter the data to obtain records for bedrock lithology layers only.

4. Click the Depth Table Filter tab. The Filter Field value must be in the same table as the Z values. Enter the following values:

   Field Name	Value
   Filter Field	[LITHOLOGY].[Graphic]
   Filter Operator	=
   Filter Comparison	bedrock
   Which Depth	First

5. Click the File Formattingtab to view formatting options:

   

   You can suppress the borehole number for each point using the Suppress PointIDs option. The Don’t Quote PointIDs field is if you are using a program that does not want quotes encasing the borehole ID. The MXRoad GenIO tab is specific for the Bentley MXROAD software and can be ignored if you are not exporting to MXROAD.

6. Click OK to export the records. The file is exported to the filename and folder you specified.

7. Open the Bedrock Surface.csv file in Excel.

   

8. Notice that again that there are X, Y and Z values followed by the borehole ID. In this case, however, the Z value is the Depth from the bedrock LITHOLOGY record for each borehole, not the Elevation from the POINT table. There needs to be one bedrock record in the LITHOLOGY table for each borehole, or bedrock data will not plot for some points.

Generating and Plotting Data in Surfer

Since you may not have Surfer on your computer, the next set of steps will be described without your performing any exercises.

Surfer is a contouring and 3D surface mapping program that converts your data into contour, surface, wireframe, vector, image, shaded relief, and post maps.

The file to be imported into Surfer is a series of randomly placed points. Boreholes are not drilled on a perfect grid, so most contouring programs have to first “grid” the data. Surfer converts the data to an equalinear grid that is evenly spaced, horizontally and vertically.

From that grid, Surfer extrapolates the Z value. For your own accuracy, it is important to compare the final model against your boreholes.

When you select a format for the grid, be aware that gINT’s modeling feature only supports a specific GS ASCII format, so to open the file later in gINT, we need to save it in that format. After the data is gridded, you can map it as a contour map and then as a surface map (the following screen shots are of surface plots):

Bedrock Surface Map

 

 

Ground Surface Map

 

To create a posting map, you need the original gINT .CSV file containing the borehole names. You can also combine the bedrock and ground surface data onto one surface plot. Try different gridding techniques to see the best way to plot your boreholes.

To generate surface data for re-import into gINT, you need to save one or more surfaces as .grd files. Refer to the Surfer documentation for instructions. We will assume that you have generated two .grd files, ground surface.grd and bedrock surface.grd. These have been supplied in the sample files so that you can continue the exercise.

Plotting Surfaces on 2D Fences

After modeling your surface data in a modeling or contouring program, you can re-import it back into gINT and plot it on a fence report. gINT cuts a profile line through each requested surface along the fence baseline.

First we need to import the two grid files (ground surface and bedrock) that were generated by Surfer. These are .GRD files, and consist of a table of Elevation or Depth values with one column for each East value plotted, and one row for each North value.

1. Verify that the Surfaces tab in INPUT is displayed (select Additional Modules->Surfaces Support if not shown).

2. Click the Surfaces tab.

3. Click the New  icon to add a new surface. You see the following dialog box:

   

4. Enter the following values:

   Field Name	Value
   Name	GROUND SURFACE
   Line Type	Solid
   Thickness	.021
   Line Color	Medium Blue
   Import Grid File	\gINT\auxiliary files\ground surface.grd

   To specify the Import Grid File, click the Browse  button on the Import Grid File field and navigate to the folder and file.

5. Click OK to import the file. Your screen should look similar to the following:

   

6. Notice the summary section at upper left. This shows the number of grid lines along the East and North axes, and the minimum and maximum values plotted on those axes. It also indicates the minimum and maximum of the depth or elevation values in the surface.

7. Notice the main table. A value appears for each intersection of an East value (column) and North value (row).

Importing the bedrock surface is comparable. Do the following:

1. Click the New  button or select File->New.

2. In the ‘New’ dialog box enter the following values:

   Field Name	Value
   Name	BEDROCK SURFACE
   Line Type	Dash
   Thickness	.021
   Line Color	Medium Red
   Import Grid File	\gINT\auxillary files\bedrock surface.grd

3. Click OK to import the file. Notice that a similar table of surface points appears.

4. Click the drop-down arrow on the object selector. Notice that both the GROUND SURFACE and BEDROCK SURFACE data tables are accessible. You can alter point values in this view if desired.

5. Click the Input tab to exit the Surface Data view.

Next we will view cross-sections of the two surfaces superimposed on boreholes in the Fences tab of the OUTPUT application group.

1. Go to OUTPUT->Fences.

2. Select the standard STRATIGRAPHY & GW - A SIZE report from the drop-down object selector.

3. Click the Browse  button to the right of the PointID field, select boreholes ‘B- 1’ through ‘B-10’, and click OK.

4. Click the Browse  button to the right of the Surfaces (2D Only) field, highlight both the BEDROCK SURFACE and GROUND SURFACE items, and click OK.

   

   A fence report will display surfaces only if 1) there is surface data present in the project for one or more surfaces, and 2) at least one of those surfaces is selected in the Surfaces (2D Only) field in OUTPUT.

5. Click the Preview  icon. When prompted for a diagram name, enter ‘Ten Boreholes with Surface’. The fence report displays:

   

6. Notice the solid blue and broken red lines for the ground and bedrock surface cross-sections, respectively.

   For each surface, the cross-section profile is where the plane of the best-fit baseline cuts the surface defined by the Surfer grid we imported.

7. Notice the legend at lower right for the surface lines. This report form includes a surface legend entity that was added in REPORT DESIGN (invoked using the Fence->Surface Legend menu item). One legend entry will appear for each surface you include in the report.

8. Notice that both surface lines end just to the right of borehole ‘B- 9’, and do not extend to ‘B-10’. To see the reason, close the preview and click the Site Layout button. The site map displays (which includes contour lines, in this case), along with superimposed point markers:

   

9. Notice that boreholes ‘B- 1’ through ‘B-10’ lie along the upper edge of the site map, and increase gradually in Y (North) value as you proceed to the right (increase in X/East).

   The two surface cross-sections follow the baseline, which is an automatic best-fit line in the present case. The baseline runs off the upper edge of the surface grid data. There is no surface in this region to “cut”, so there is no profile to plot.

10. To correct the problem, select Fence Spec->Draw Baseline and draw a line just below the 10 points. Click OK to save the new baseline, then click the Return to Output tab.

11. Click the Preview icon again, and notice that the two surface lines are now complete.

    

Keep in mind that the contouring algorithm can match your control points, but lose consistency and accuracy between the points.

See Also

Help->Index->Exporting Data to a Contouring Program

Help->Index->Import Grid File