Calculate the maximum difference between a grid cell and it's neighbours

Summary

Using a 'kernal file' will restrict the analysis to the neighbours surrounding the cell currently being processed. Some simple mathematical evaluations will lead to the final result.

Procedure

1. Create a text file (any_name.txt) with the following four lines:
   
   

      3 3
      1 1 1
      1 0 1
      1 1 1 

   
   Make sure you type a return after the last number.
   
   
2. Determine the maximum and and minimum values around the cell.
   
   

   Code:
     Grid: fmax = FOCALMAX (in_grd, IRREGULAR, donut.txt)
     Grid: fmin = FOCALMIN (in_grd, IRREGULAR, donut.txt) 
   

   
   
3. Determine the difference between the cell and the max/min values.
   
   

   Code:
     Grid: diffmax = ABS (fmax - in_grd)
     Grid: diffmin = ABS (in_grd - fmin)

   
   
4. Assign the maximum difference to the output grid.
   
   

   Code:
     Grid: finaldiff = MAX (diffmax, diffmin)