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| How can I remove a trend surface from my data (ie. flatten a sloping surface)? |
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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:
- Use Grid | Data and grid your data using your desired gridding method and options.
- Go back to Grid | Data, select your data file again and click Open.
- In the Grid Data dialog box, choose the Polynomial Regression gridding method.
- Click on the Advanced Options button, specify the order of the trend surface and click OK.
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Make sure the Grid Line Geometry section has the same Minimum, Maximum, and # of lines in the X and Y direction as your original grid file.
- Specify a new grid file name and click OK .
- Go to Grid | Math.
- In the Grid Math dialog, click the Add Grids button.
- Select both grids and click Open.
- Make sure the original grid has the variable A and the polynomial regression grid has the variable B.
- Click the yellow Open Folder icon to the right of Output Grid File, and specify a new grid file name and location and click Save.
- Enter the function A - B and click OK.
- The new grid file will be the original data minus the trend.
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