# Restrict the Z limits of a 3D surface map in Surfer

If you want to limit a 3D surface to a smaller range of Z values than is currently shown, you can use Grids | Calculate | Math to either assign NoData values to the areas above and below certain Z values, or convert all values above/below a threshold value to that value. Which process you choose depends on how you want the map to look in the areas outside the limits you want.

For example, let's say you want to limit the surface map to a maximum Z value of 580 (eliminating the peaks).

Method 1: Assign NoData

1. Click Grids | Calculate | Math.
2. In the Grid Math dialog, click the Add Grids button.
3. Select your grid file and click Open.
4. In the Grid Math dialog, enter the following function into the Enter a function... box: If (A<580, A, 1.70141e+38). This tells Surfer that if a Z value in grid A is below 580, then use that Z value in the output grid, otherwise use the NoData value.
5. Click OK and the new grid is created.
6. Create a new map from this new grid or replace the grid for the existing 3D Surface layer with this new grid.

Assign values above and below a threshold value NoData. These areas then become invisible in the 3D surface map.

Method 2: Limit to threshold value

1. Click Grids | Calculate | Math.
2. In the Grid Math dialog, click the Add Grids button.
3. Select your grid file and click Open.
4. In the Grid Math dialog, enter the following function into the Enter a function... box: If (A<580, A, 580). This tells Surfer that if a Z value in grid A is below 580, then use that Z value in the output grid, otherwise use the NoData value.
5. Click OK and the new grid is created.
6. Create a new map from this new grid or replace the grid for the existing 3D Surface layer with this new grid.

Assign values above and/or below a threshold value to that value.

If you would like a way to set the z axis limits for a 3D map without having to modify the grid, you can email surfersupport@goldensoftware.com to add your vote to this request on the suggestion file.

Updated December, 2021