To calculate the slope as a percentage from a grid file, follow these steps:
- Click Grids | Calculate | Calculus.
- Select the grid file and click Open.
- In the Grid Calculus dialog, choose Differential & Integral Operator | Gradient Operator.
- Specify the Output Grid file name and file path.
- Click OK. This creates a new grid file of the slopes. The slopes are reported as a number (rise over run). The Z value is 0 for a horizontal surface, and approaches infinity as the slope approaches vertical.
- To convert this to a percentage, click Grids | Calculate | Math.
- In the Grid Math dialog, click the Add Grids button.
- Select this gradient grid file and click Open.
- Multiply the grid by 100 by entering the function A*100.
- Save the file.
- To save the results to a data file, click the yellow Change Filename icon to the right of Output Grid. Give the file a name, and select to save it as a DAT XYZ file and click Save.
- To save the results to a grid file, click the yellow Change Filename icon to the right of Output Grid. Give the file a name, leave the Save as type set to GRD Surfer 7 Binary Grid, and click Save.
- Click OK and the file is created.
Updated February 9, 2017