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drlead

Surfer8.09 Get krigged values from one grid to another grid

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I have a grid file with 512 geocoded, irregularly spaced locations. I have another grid file with 20 geocoded, irregularly spaced locations, which by and large overlap the first set of locations but don't fall at the same latitude,longitude coordinates. I want to use my z-axis measurements from the 20 location file to construct a krigged map, then apply the calculated krigged values to the first set of locations and save the krigged values interpolated to the data file with the 512 locations.

I guess I could use the grid file editor and try to hand mark all the 20-location krigging estimates to each of the 512 spatial locations in the other file, but this would be tedious and prone to error. Is there a way to automate this process in Surfer8 or in any later version?

Many thanks in advance,

Steve (drlead)

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Hi Steve,

Use the Grid | Residuals menu command to extract the values from a grid file at the locations in an XYZ data file.

Open the data file that contains the target XY values, add a column of zeros. Surfer needs this for the Grid | Residuals command because it subtracts the values in the grid file from the values in the data file and writes out the residuals or differences. The results will be the negative of the values in the grid file, but you can multiply them by -1 to get them to be the positive or actual values.

  1. Open the target data file in the Surfer worksheet.
  2. Choose the Data | Transform menu command and create a new column full of zeros. If column D is blank, use the formula D=0 to do this quickly. Save the results to a new file name.
  3. Click back to the Plot Window and choose the Grid | Residuals menu command. Specify the name of the GRD file, the name of the data file (or the Open Worksheet file if you have that option in your version of Surfer), and the columns containing the X, Y, zeros, and residuals. The results will be displayed in a new worksheet window.

Thanks,

Tom B

RockWare Inc

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Tom, thanks for the detailed instructions. I'm still waiting for the 20 point data set, but as soon as I get it I'll try what you suggested and report back to the forum.

Best,

Steve (drlead)

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