On mardi 30 avril 2019 15:17:30 CEST Erik Ravhed wrote:

> Hi all,

>

> I have a question regarding EPSG:3034 and its axis ordering. According

> to

https://www.epsg-registry.org the order of the axes should be ordered

> as northing easting. Looking at the proj4 definition it is defined as

> the following:

>

> +proj=lcc +lat_1=35 +lat_2=65 +lat_0=52 +lon_0=10 +x_0=4000000 +y_0=2800000

> +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

>

> Looking at this definition I don't see how I can determine that

> EPSG:3034 should be treated as a northing easting. Shouldn't |+axis=neu|

> be a part of the proj4 definition?

>

Presumably, but proj strings will remain like that forever at that point of

history, since axis order of projectedCRS was never a concern in PROJ < 6 era,

and a lot of users of those code still wanted easting, northing order whatever

EPSG said.

PROJ 6 is now fully axis aware, so when doing a transformation from ETRS89

lat/long to EPSG:3034, you get:

$ src/projinfo -s EPSG:4258 -t EPSG:3034 -o PROJ

PROJ string:

+proj=pipeline +step +proj=axisswap +order=2,1 +step +proj=unitconvert

+xy_in=deg +xy_out=rad +step +proj=lcc +lat_0=52 +lon_0=10 +lat_1=35 +lat_2=65

+x_0=4000000 +y_0=2800000 +ellps=GRS80 +step +proj=axisswap +order=2,1

So you have a first axisswap operation to go from input lat,long to internal

long,lat, then the map projection, and then another axisswap operation to go

from te internal easting,northing to final northing,easting

Even

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