Surfer grids do not store coordinate system or projection information internally. If the associated projection files (GSR2, PRJ, etc.) are lost, it is not possible for Surfer to determine the proper coordinate system.  Therefore, the lost projection files will not be recreated automatically.

If the projection files have been lost due and you know the source coordinate system for the grid files, you can recreate the projection files using the steps below:

1. Click Grids | Edit | Assign Coordinate System.
2. In the Open Grid dialog, select your grid file and click Open.
3. In the Assign Coordinate System dialog, navigate to the appropriate coordinate system (e.g. Predefined | Projected  Systems | UTM | North America | North  America  NAD83  zone  10N).
4. Click OK.