Applying a Minimum Area Filter to a Grid Model

RockWorks | Utilities | Grid | Filters | Minimum Area

This program will read either a Boolean or a conventional grid model and evaluate contiguous cells that exceed a user-defined area. If the area of a group of contiguous cells is less than a user-defined threshold, the nodes will be set to zero. This provides a means for eliminating exploration targets that are too small.

Menu Options
Step-by-Step Summary

Menu Options

• Input Columns:  If you request plotting of 2D map symbols (below) AND if you have data loaded into the Utilities datasheet, you can use these prompts (along the left edge of the Options window) to specify the X and Y locations for the map symbols.  If you don't plot map symbols, these will be ignored.
  • X (Easting): Click here to select the name of the column containing the X or Easting  coordinates.
  • Y (Northing): Click here to select the name of the column containing the Y or Northing coordinates.
    
    
• Input Model: Click to the right to browse for the name of the existing grid model (.RwGrd) that is to be filtered.  This can be a real number or Boolean grid model.
• Output Model: Click to the right to type in a name for the filtered grid model the program will create.
  
  
• Minimum Value: Click here to type in the minimum Z value in the grid file to be considered.  All higher values will be run through the filter.  For example, if you are analyzing an input file that contains Boolean ("0" or "1") values, and you wish to compute areas only for the nodes assigned a "1", you could enter "1" here.  Or, if you are analyzing a real number grid model, and you wish to compute areas only for nodes with geochemical values of 7.5 and higher, you would enter "7.5" here.
• Minimum Area: Click here to type in the minimum allowed area occupied by contiguous nodes with values greater than or equal to the declared minimum.  This value will represent square units.  For example, to filter out all material zones that occupy less than 1500 square feet, you would type in "1500". 
  
  
• Create 2-Dimensional Grid Diagram: Insert a check in 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 the Grid menu is visible.
3. If you'll be creating a 2D map with sample location (well) symbols, you can use the File | Open option to open the .RwDat file containing the X and Y location coordinates for the map symbols.  
4. Select the Grid | Filters | Minimum Area menu option.
5. Enter the requested menu settings, described above.
6. Click the Process button to continue.

The program will read the input model and determine the contiguous areas of values that exceed the declared minimum Z value.  Those contiguous areas that fall below the declared minimum area will be re-assigned a Z value of zero.  The resulting model will be stored on disk under the output grid file name.

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.

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

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