You can change the grid minimum value to 0 using Grid Math. To do this:
- Click Grids | Calculate | Math.
- In the Grid Math dialog, click the Add Grids button, select the grid file and click Open.
- Specify a new name for the Output Grid File, if desired.
- Enter the function max(A,0) to replace all negative values with 0, or you can use the function IF(A=-9999.99, 0, A) to specifically replace only -9999.99 with 0 (leaving other negative values alone)
- If you want to add the new grid to the active project check Add grid as layer to:, select either [New Map] or [Map], and select the layer type in the New layer type drop down menu.
- Click OK and the new grid file is created.
Updated January 26, 2017