Take the 2-minute tour ×
Geographic Information Systems Stack Exchange is a question and answer site for cartographers, geographers and GIS professionals. It's 100% free, no registration required.

The GeoJSON spec says "The default CRS is a geographic coordinate reference system, using the WGS84 datum, and with longitude and latitude units of decimal degrees". It doesn't say seem to specify what the units of elevation/altitude/z are for points.

Is there a default unit of altitude for GeoJSON? If not, are there common conventions, or a way to specify units?

share|improve this question
Welcome. It is meters: wiki.geojson.org/RFC-001. Make a search for "z" and look at the second result. –  Andre Silva Jun 14 '13 at 0:02
Interesting that the specification doesn't give any 3d examples. –  Fezter Jun 14 '13 at 0:55
Andre, RFC-001 says "This is historical material. This page has been superseded by RFC-2", and RFC-2 doesn't include that bit about z being in units of meters. –  John Wiseman Jun 14 '13 at 7:11
Not entirely surprising, GeoJSON is designed to be as simple as possible. Things like Z/M values and CRSes are useful, but much less commonly used and covered, though that is likely to change. –  scw Jun 14 '13 at 7:20

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Browse other questions tagged or ask your own question.