Remove a trend across a surface (i.e. flatten a slope) in Surfer

Surfer can use the polynomial regression gridding method to calculate a grid file representing the trend of a surface, and then you can use Grid Math to remove that trend from your original grid file.


To remove a first or second order trend surface from a grid file, follow these steps:

  1. Click Home | Grid Data | Grid Data, select your data file and click Open.
  2. Select your desired gridding method and options. Note the Minimum, Maximum, and # of Nodes in the X and Y directions, and click OK.
  3. Click Home | Grid Data | Grid Data again, select your data file again and click Open.
  4. This time, select the Polynomial Regression gridding method.
  5. Click the Advanced Options button, specify the order of the trend surface and click OK.
  6. Make sure the Grid Line Geometry section has the same Minimum, Maximum, and # of Nodes in the X and Y directions as your original grid file.
  7. Specify a new grid file name and click OK.
  8. Click Grids | Calculate | Math.
  9. In the Grid Math dialog, click the Add Grids button.
  10. Select both grids and click Open.
  11. Make sure the original grid has the variable A and the polynomial regression grid has the variable B. 
  12. Click the yellow Change Filename icon to the right of Output Grid, and specify a new grid file name and location and click Save.
  13. Enter the function A - B and click OK. The new grid file will be the original data minus the trend.


Updated October 16, 2018


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