When to specify a coordinate system for every map layer in Surfer

In Surfer, you only need to specify the coordinate system for the layers and the map if:

1. You are going to be using a different coordinate system for the map than the layers; or
2. If you are adding layers from files in different coordinate systems.

If either case above is true, then the coordinate system for each layer in the map should be specified, and the coordinate system for the map should also be specified.

If all layers use the same coordinate system as the map and you want to export it to a georeferenced file (i.e. KML, GeoTIFF, GeoPDF, etc), then you only need to specify the coordinate system for the map (not the layers).

You can assign the coordinate system of the Map to all layers by selecting the Map in the Contents window, clicking the Coordinate System tab in the Properties window, and clicking the Assign Now button. That will assign the coordinate system of the map to all unreferenced layers in the map. This may be useful if you may want to convert the coordinate system of the map in the future, or potentially add other layers in different coordinate systems.

If all your layers are in the same coordinate system as each other and the map, and you are not going to change the coordinate system for the map or export it to a georeferenced file, then you do not need to specify the coordinate system for the layers or the map.

Updated November 2021