Resample, resize, or crop a grid file in Surfer

Surfer includes three ways to resize (clip/crop/extend) or resample a grid to specified XY extents or a specified number of grid rows and columns:

Method 1: Grid Extract. This is a good option if you want to shave off a few rows and/or columns, if you want to thin the grid by reading every nth grid node, or you know exactly which rows and columns you want to extract from the grid. This command only works in grid rows and columns (not XY extents).

1. 1. Click Grids | Resize | Extract,
   2. In the Extract Grid dialog, select a grid file in the Input Grid menu or click Browse, select a grid file and click Open.
   3. You can clip grid nodes off sides, top and bottom of the grid by increasing the First or decreasing the Last values, or you can filter the grid by setting the Read Every to a higher value. This method does not resample the grid file, it simply removes vertical or horizontal lines of grid nodes to resize the grid.
   4. Change the Output Grid, if desired.
   5. Choose to Add grid as layer to:, if desired. 
   6. Click OK.

Method 2: Grid Smooth. This is a good option if you want to resample the grid. You can insert nodes to increase the resolution, or you can recalculate the grid to have a different number of rows and/or columns. 

1. Click Grids | Edit  | Spline Smooth.
2. In the Spline Smooth dialog, select a grid file in the Input Grid menu or click Browse, select a grid file and click Open.
3. Change the Method to Recalc Grid, change the Final Grid Size to the desired number of rows and columns. A spline method is used to recalculate the grid node values.
4. Change the Output Grid, if desired.
5. Choose to Add grid as layer to:, if desired. 
6. Click OK.  

Method 3: Grid Mosaic. This is a good option if you want to resample the grid by changing the grid spacing, the number of rows and/or columns, or the X or Y min/max values for the grid. This is the most common way to resample or resize/crop a grid file.

1. Click Grids | Resize | Mosaic, specify the input grid file and click Open to display the Grid Mosaic dialog. 
2. Change the Output Grid Geometry to the desired values. You can change the Minimum, Maximum, Spacing or the # of Nodes. 
3. Select the desired Resampling Method, either Nearest Neighbor, Bilinear Interpolation, or Cubic Convolution. In most cases, the default Bilinear Interpolation is best.
4. Change the Output Grid File, if desired, to change the file type and name.
5. Choose to Add grid as layer to:, if desired. 
6. Click OK.  

Updated November, 2021