When importing grid files from other programs into Surfer, it may be necessary to define the blanking value (null value, NoData value) so that it will be recognized.  The script provided below converts the Blank Value in a grid file header to another value. This is the Z value that is considered blanked by Surfer. This does not change the Z values of any nodes in the grid file.

To run this script:

1. Copy the text below, or download the attached BAS file: BlankValue.bas.
2. In a Windows Explorer window, navigate to C:\Program Files\Golden Software\Surfer.
3. Double click on Scripter.exe to launch Scripter.
4. Press Ctrl+A to select all of the existing lines then press Delete.
5. If you copied this script, press Ctrl+V to paste it into Scripter. If you downloaded it, click File | Open, select the BAS file from your downloads directory, and click Open.
5. Edit the value on line 24 to match the value in the grid file you want Surfer to treat as NoData.
6. Click Script | Run to run the script.
    

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'Converts the blank value in a grid to a different value. This is the number that Surfer
'considers blanked, so all nodes with this number as the Z value will be blanked in Surfer.
'This is different from Blank0.bas, which simply replaces the Z value
'of blanked nodes with another number, leaving the actual blank value in the grid the same.
Sub Main
Debug.Clear
	Dim SurferApp As Object
	Set SurferApp = CreateObject("Surfer.Application")
	SurferApp.Visible = True
	Set Plot = SurferApp.Documents.Add(srfDocPlot)
	Set Shapes = Plot.Shapes
	Set Grid = SurferApp.NewGrid
'Choose a grid file
	gridfilepath = GetFilePath( , "grd",SurferApp.Path+"\samples\","Open Grid File",0)
	Set Grid2 = Grid.LoadFile(gridfilepath,False)
'Sets the BlankValue of the grid. All nodes with a Z value exactly equal to the BlankValue will be considered blanked by Surfer.
	Grid.BlankValue = -32767
'Saves the grid to a new name
	gridfilepath = Left(gridfilepath,InStrRev(gridfilepath,".")-1) + "_BlankValue.grd
	Grid.SaveFile(gridfilepath, srfGridFmtS7)
	Debug.Print "File saved as ";gridfilepath
'Creates a contour map of new grid
	Shapes.AddContourMap(gridfilepath)
End Sub

Updated November 2021