Creating a Grid Aspect Map

RockWorks | Utilities | Grid |
Directional Analyses | Grid -> Aspect Map

This program reads a grid model (.RwGrd file) and computes the changes in Z-values (elevations, concentrations, etc.) between neighboring nodes, noting the direction (0 to 360) of downhill slope.  The resulting direction or "aspect" values are stored in a new grid model, with options for generating a 2D map, 3D surface, and a grid statistics report.

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 the right to browse for the name of the existing grid model (.RwGrd file) to be analyzed and displayed as an Aspect map.  
• Normalize Nodes Prior to Analysis:  Leave this unchecked if your grid model represents topographic elevations. 
  If your grid model represents something other than topography (e.g. geochemical concentrations), you should check this box so that the Z values can be normalized to map units prior to computing aspect.  For example, if a grid node spacing is 10 meters and the user is analyzing geochemical data than ranges between zero and 0.01, the maximum slope would be less than one degree in which case the program would produce a blank diagram. With normalization, however, the data is now rescaled to resemble a three-dimensional cube in which the slope will have a wide range (i.e. zero to 90 degrees).
  • Automatic: Using this normalization scheme, the program will rescale the grid node values such that the minimum node value will represent zero while the maximum node value will be equal to the map distance from the southwest corner to the northeast corner of the grid model.  The example below illustrates an aspect map based on normalized geochemical data that initially ranged between zero and 0.01.

  

  • Manual: Choose this option if you want to enter your own min and max range within which the grid node values are to be normalized before the analysis is run.
• Output (Aspect) Grid: Click here to type in the name to assign to the new grid model that will be created, with node-to-node slope direction computations recorded for the Z values.
  
  
• Create 2-Dimensional Grid Diagram: Check this check-box if you want to display the output grid as a 2D map at this time.  Expand this heading to set up the 2D map layers (bitmap, symbols, labels, line contours, color-filled contours, labeled cells, and/or map border).
• Create 3-Dimensional Grid Diagram: Insert a check in this check-box if you want to display the output grid as a 3D surface.  Expand this heading to set up the 3D map layers (flat surface, Boolean colors, perimeter, reference cage).  You can request both a 2D and 3D representation of the grid model.
• Create Grid Statistics Report: Insert a check here if you want to see a report summarizing the output grid. 
  • Include Standard Deviation:  Check this box if you want the report to include standard deviation.
  • Include Directional Analysis:  Check this box to include slope, aspect, and strike computations. Be warned that these can take a few moments for large grid models.
     

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. It is not necessary to open a datasheet.
3. Select the Grid | Directional Analyses | Grid -> Aspect Map 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, storing the down-slope direction (0 to 360 azimuth) for each node in the specified units in the output grid file. 

The requested diagram(s) will be displayed in a RockPlot2D tab and/or RockPlot3D tab in the Options window.   If you requested a statistics report, it will be displayed in a Text Tab in the Options window.

6. You can adjust any of the settings in the Options window (input grid model name, map settings, etc.) and then click the Process button again to regenerate the map.
   ! Each time you click the Process button, the existing display will be replaced. 
    
7. View / save / manipulate / export / print the map in the RockPlot2D or RockPlot3D window. 
   
   

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