FAQ

Which file formats does PROJ support?

The command line applications that come with PROJ only support text input and output (apart from proj which accepts a simple binary data stream as well). proj, cs2cs and cct expects text files with one coordinate per line with each coordinate dimension in a separate column.

Note

If your data is stored in a common geodata file format chances are that you can use GDAL as a frontend to PROJ and transform your data with the ogr2ogr application.

Can I transform from abc to xyz?

Probably. PROJ supports transformations between most coordinate reference systems registered in the EPSG registry, as well as a number of other coordinate reference systems. The best way to find out is to test it with the projinfo application. Here’s an example checking if there’s a transformation between ETRS89/UTM32N (EPSG:25832) and ETRS89/DKTM1 (EPSG:4093):

$ ./projinfo -s EPSG:25832 -t EPSG:4093 -o PROJ
Candidate operations found: 1
-------------------------------------
Operation n°1:

unknown id, Inverse of UTM zone 32N + DKTM1, 0 m, World

PROJ string:
+proj=pipeline +step +inv +proj=utm +zone=32 +ellps=GRS80
+step +proj=tmerc +lat_0=0 +lon_0=9 +k=0.99998 +x_0=200000 +y_0=-5000000 +ellps=GRS80

See the projinfo documentation for more info on how to use it.

Coordinate reference system xyz is not in the EPSG registry, what do I do?

Generally PROJ will accept coordinate reference system descriptions in the form of WKT, WKT2 and PROJ strings. If you are able to describe your desired CRS in either of those formats there’s a good chance that PROJ will be able to make sense of it.

If it is important to you that a given CRS is added to the EPSG registry, you should contact your local geodetic authority and ask them to submit the CRS for inclusion in the registry.

I found a bug in PROJ, how do I get it fixed?

Please report bugs that you find to the issue tracker on GitHub. Here’s how.

If you know how to program you can also try to fix it yourself. You are welcome to ask for guidance on one of the communication channels used by the project.

How do I contribute to PROJ?

Any contributions from the PROJ community is welcome. See Contributing for more details.

How do I calculate distances/directions on the surface of the earth?

These are called geodesic calculations. There is a page about it here: Geodesic calculations.

What is the best format for describing coordinate reference systems?

A coordinate reference system (CRS) can in PROJ be described in several ways: As PROJ strings, Well-Known Text (WKT) and as spatial reference ID’s (such as EPSG codes). Generally, WKT or SRID’s are preferred over PROJ strings as they can contain more information about a given CRS. Conversions between WKT and PROJ strings will in most cases cause a loss of information, potentially leading to erroneous transformations.

For compatibility reasons PROJ supports several WKT dialects (see projinfo -o). If possible WKT2 should be used.