You can import a GeoTIFF into Surfer in UTM units and convert the coordinates of the map to display Lat/Long. To do this:
- Click Home | New Map | Base | Base.
- Select the GeoTIFF file and click Open. The base map is created and the coordinates are referenced according to the image referencing saved internally in the TIF.
- Select Base in the Contents window and click the Coordinate System tab in the Properties window. If the referencing also included coordinate system information, it is automatically entered here.
- If there is no coordinate system information entered here, click the Set button, navigate to Predefined | Projected Systems | UTM then select the appropriate datum or region and the appropriate zone. Click OK.
- Select Map in the Contents window and click the Coordinate System tab in the Properties window.
- Click the Change button.
- Select the appropriate Lat/Long coordinate system you want (usually Predefined | Geographic (lat/lon) | <your preferred datum>) and click OK. Now the image base map is converted to lat/long for display in the plot window.
- If you want a new GeoTIFF referenced in lat/long, turn off the axes by unchecking them in the Contents window and then click File | Export and export to a TIF file, saving the spatial reference information internally.
Updated October 31, 2018