Creating a Grid-Based Stereonet Diagram

RockWorks | Utilities | Grid |
Directional Analyses | Grid -> Stereonet

This program reads a grid (surface) model and computes the changes in Z-values (elevations) between neighboring nodes (slope), noting the direction (0 to 360) of steepest change (= "aspect").  It then creates a stereonet diagram to summarize the directionality of the aspect bearings (dip direction) and the steepness of the slopes (dip angle).

Note: This program requires that a RockWorks surface (grid) model already exist. 

Menu Options
Step-by-Step Summary

Menu Options

• Input (Surface/Terrain) Grid: Click to browse for the name of the existing grid model (.RwGrd file) to be analyzed and displayed as a stereonet diagram.  

Stereonet Options (See the Details topic for more information about these stereonet-specific settings)

• Projection: Determines how data are to be projected on the stereonet plot, as an equal angle or Wulff projection, or as an equal area or Schmidt projection. A lower hemisphere projection is used for both types.
  ! Note Stereonet contours (activated below) are based on point distributions within a Schmidt projection (equal area) diagram.  If you plot points on a Wulff stereonet AND include contours, you may note that the point densities and contours might not correspond.
• Contour Lines: Insert a check in this check-box to activate the plotting of line contours on the diagram to represent point density. Expand this item to access the contouring settings. If you request contours, they will be drawn based on a program-computed grid model; be sure you establish the Gridding Options (see below). 

• Colored Intervals: Insert a check in this check-box to activate the plotting of color-filled intervals to represent point density on the diagram. Expand this item to access the colorfill settings. As with the line contours, above, the color intervals will be drawn based on a program-computed grid model.
• Great Circles: Use this check-box and it settings to activate the plotting of planar data as great circles. Expand this item to select the line styles.

• Mean Lineation Vector: To activate the plotting of the mean lineation vector, insert a check in this box. Expand this to select a symbol to represent it on the plot, and the label
• Best Fit Circle: Insert a check in this box to activate the plotting of the program-computed best-fit great circle on the stereonet. Expand this item to select its line style and color.
• Title: Check this to activate the plotting of a diagram title, and expand this to enter the text, color, size, and position.
• Statistics : Check this item to plot a statistical legend for the data. Expand this item to select text size and color. (See the Statistical Summary.)
• Background: Expand this option to turn on and off a variety of reference lines, ticks, and labels.
• The Gridding Options and Density Units items in the Stereonet Options window are used to establish how the point densities are to be computed if either line or color-filled contours have been requested on the stereonet plot. The program uses a process of "gridding" to compute point densities, in a manner similar to the gridding process for creating maps. The methods used to extrapolate the grid node values in a stereonet differ from the methods used in mapping, however. To access these settings, expand the Gridding Options item.  For "basic" gridding, you might select the Step Function method, with density units in Percent. See Stereonet Gridding Options for a lengthy explanation.
  ! Note Stereonet contours are based on point distributions within a Schmidt projection (equal area) diagram.  If you plot points on a Wulff stereonet AND include contours, you may note that the point densities and contours might not correspond.
   

Step-by-Step Summary

1. Be sure you have a RockWorks grid model already created, for input into this program.
2. Access the RockWorks Utilities program tab so that you can see the Grid menu commands. It is not necessary to open a datasheet.
3. Select the Grid | Directional Analyses | Grid -> Stereonet menu option.
4. Enter the requested menu settings, described above.
5. Click the Process button to continue.

The program will read the input grid model, compute the slope and aspect for each node, and determine the dip direction and slope angle for each node.  It will then generate a stereonet diagram to represent the distribution of the node directionality. The stereonet diagram will be displayed in a RockPlot2D tab in the Options window.  

6. You can adjust any of the settings in the Options window (input grid model name, diagram settings, etc.) and then click the Process button again to regenerate the diagram.
   
   ! Each time you click the Process button, the existing display will be replaced. 
    
7. View / save / manipulate / export / print the diagram in the RockPlot2D  window. 
   
   

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