Calculate slope as a percentage in Surfer

1. Click Grids | Calculate | Calculus.
2. Select the grid file and click Open.
3. In the Grid Calculus dialog, choose Differential & Integral Operator | Gradient Operator.
4. Specify the Output Grid file name and file path.
5. 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.
6. To convert this to a percentage, click Grids | Calculate | Math.
7. In the Grid Math dialog, click the Add Grids button.
8. Select this gradient grid file and click Open.
9. Multiply the grid by 100 by entering the function A*100.
10. Save the file:
    1. 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.
    2. 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.
11. Click OK and the file is created.

Updated November, 2021