How can I make a residual map in Surfer?

Residual maps can be used to highlight anomalies such as faults, structural trends, and structural horizons in mostly flat stratigraphy and topography surfaces.  The benefits of this type of analysis are discussed in the 2008 Oil & Gas Journal article Trend surface residual anomaly mapping and well data may be underutilized combo. To make a trend surface residual anomaly map or # order residual map in Surfer, complete the steps below:

1. Click Home | Grid Data | Grid Data, select the data file in the Dataset1 section and assign the appropriate XYZ columns. 
2. In the Gridding method section, select Kriging, or your preferred gridding method.
3. Click OK to generate the grid (and click OK when notified that the grid was created).
4. Click Home | Grid Data | Grid Data again, select the data file in the Dataset1 section and assign the appropriate XYZ columns. 
5. In the Gridding method section, select Polynomial Regression.
6. Click Next. 
7. On the Grid Data Polynomial Regressions - Options page, specify the surface definition as shown below, then click OK. 
   • For 1^st order residual, select Simple planar surface as the Surface Definition.
   • For 2^nd order residual, select Quadratic surface as the Surface Definition.
   • For 3^rd order residual, select Cubic surface as the Surface Definition.
   • For 4^th order residual, select User defined polynomial as the Surface Definition, and then enter 4 for the Parameters.
8. Click Skip to End.  
9. Click Finish to generate the grid (and click OK when notified that the grid was created).
10. Click Grids | Calculate | Math.
11. Click the Add Grids button.
12. Select the first grid, hold CTRL on your keyboard and click the second grid. Click Open.
13. In the function box, subtract the surface grid from the original grid:
    
14. Choose to add your layer as a new map or to an existing map as well as the map type and click OK. 

Updated November 2021