To assign NoData to a post map outside of a polygon:
- Select your map.
- Click Home | Add to Map | Layer | Base from Data.
- Select the data file used to create your post map, and click Open.
- Set the data row and column properties in the Base from XY Data dialog, then click OK.
- In the Contents window, click on the Base(vector) layer.
- If your area of interest or polygon is rectangular:
- Click Home | Selection | Select All | Block Select.
- Click and drag your mouse around the group of points on the map that you are interested in.
- Click Home | Selection | Select All | Invert Selection.
- Press DELETE on the keyboard to delete all selected points (outside the area of interest).
- If your area of interest is not rectangular:
- In the Contents window, click the pin icon next to the Base layer to limit selection to that layer.
- Click on the base layer in the Plot window.
- Click and drag your mouse around groups of points on the map which are outside of the polygon to mass-select them
- Press DELETE on your keyboard to delete them.
- Repeat steps 7.3 & 7.4 until only the points you're interested in remain. Alternatively, hold SHIFT while completing step 7.3 to select multiple groups of points before deleting.
- In the Contents window, ensure the Base layer containing your points is selected.
- Click File | Export.
- In the Export dialog, check the box next to Selected objects only.
- Change the Save as type to DAT XYZ (*.dat, *.txt, *.xyz), give your file a name, and click Save.
- In the Export Options dialog, on the Scaling page set the Scaling source to your Map.
- Click OK to create the DAT file.
- Click the File | Open in Worksheet command to open the DAT file in Surfer's worksheet.
- Select Column C and click Data | Data | Text to Number.
- Click File | Save to save the DAT file.
If you would like to add your vote to our suggestion file for a way to blank a post map outside of a polygon, contact firstname.lastname@example.org.
- Remove all points outside a polygon in a Surfer Post map or Base map
- Interactively edit/remove points from a data set or post map in Surfer
Updated December 20, 2021
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