[PROJ] Coordinates in Lat/Lon or Lon/Lat

[Kristian Evers]

Alain,

See the FAQ [0] for an answer to your question about axis ordering. In short, everything works as intended but for historical reasons it seems a bit weird.

/Kristian

[0] https://proj.org/faq.html#why-is-the-axis-ordering-in-proj-not-consistent

From: PROJ <proj-bounces at lists.osgeo.org> On Behalf Of Alain Orsoni
Sent: 14. april 2023 08:29
To: PROJ at lists.osgeo.org
Subject: [PROJ] Coordinates in Lat/Lon or Lon/Lat

Hello,

Basic question but necessary for me :

We use PROJ Version 8.2.1
Exemple : I convert from Longitude=10 Latitude=70 from 4326 to UPS stereo North Pole (5041)

projinfo -s EPSG:4326 -t EPSG:5041 -o PROJ
Gives output :

+proj=pipeline
  +step +proj=axisswap +order=2,1
  +step +proj=unitconvert +xy_in=deg +xy_out=rad
  +step +proj=stere +lat_0=90 +lon_0=0 +k=0.994 +x_0=2000000 +y_0=2000000
        +ellps=WGS84


But
echo "10 70 0" | cs2cs EPSG:4326 EPSG:5041


Gives output : 11976062.58             -1630989.83 0.00
The good result given by EPSG.IO is  : 2389386.90                                  -208322.83 0.00
I get the good result with : echo « 70 10 0" | cs2cs EPSG:4326 EPSG:5041

So it seems that the syntax. cs2cs EPSG:4326 EPSG:5041  doesn’t apply the step axisswap

Can someone confirm this behavior ?

Second question :
In C++ API the proj_create_crs_to_crs() associated to  proj_normalize_for_visualization() allows to avoid this problem.
But we use also PROJ in shell scripts. It seems to me that some geodetic_crs expect lat-lon entry and some other Lon-lat.
Is there a way in the SQL database (proj.db) to find this information?

Thanks for any answer.

Alain



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