I have two digital elevation models. One’s datum is in WGS84, and the other datum is WGS84 UTM 15N. I am using both for geologic mapping.

  1. What’s the difference between the two datum?
  2. Is it okay for me to use both DEMs in conjunction even though they are using different datum’s (will it introduce an errors in my measurements?)?
  • 1
    You're comparing two different things. Datum != Projection, and GeographicCoordRef != ProjectedCoordRef.
    – Vince
    Oct 5, 2022 at 1:20
  • 6
    They both use the same datum - WGS84. One DEM is in a unprojected, geographic coordinate reference system (CRS) that uses decimal degrees as its horizontal units, the other is in a projected (UTM) CRS and uses metres as the horizontal units. Whether you can use them at the same time depends on what you are trying to do. If just for visualisation, yes, because your GIS can reproject on the fly. If you're doing any kind of calculations, e.g. slope, you should project the DEM with the geographic CRS.
    – user2856
    Oct 5, 2022 at 4:18
  • Thank you so much. Do you have any references that might be helpful in explaining this more? Anything is appreciated Oct 5, 2022 at 12:33

1 Answer 1


Both dataset have the same datum but the difference is only WGS84 have longitude and latitude as measurement units whereas WGS84 UTM 15N is projected coordinate system and measurement units for Projected coordinate system are in meters/km/mile etc.

Not the answer you're looking for? Browse other questions tagged or ask your own question.