You can choose lat/long as either your source or target coordinate system in the Surfer worksheet using Data | Coordinate System | New Projected Coordinates, or you can assign lat/long as the coordinate system for a data file using Data | Coordinate System | Assign Coordinate System. To select lat/long, expand Geographic (lat/lon) in the Assign Coordinate System dialog and select the appropriate datum.
- In the Surfer worksheet, click Data | Coordinate System | New Projected Coordinates.
- In the New Projected Coordinates dialog, click the (...) button next to either Source Coordinate System or Target Coordinate System (whichever you want to specify at lat/long).
- In the Assign Coordinate System dialog, open the Predefined | Geographic (lat/lon) category.
- Many different datums are listed under this category. Select the datum your lat/long coordinates use. Most simple lat/long coordinates use World Geodetic System 1984 (aka. WGS84) as the datum.
- Click OK and the lat/long coordinate system is entered, in this case as the Target Coordinate System.
Updated November 10, 2017