How can I add custom CRS with +proj=mercxx to QGIS 2.2.0 Valmiera?

Question

i've builded a custom proj.4 library, tested it by command line (proj and cs2cs) and with postgres/postgis. All works fine.

Now i'm trying to make the same with Qgis 2.2.0. I've replaced the original proj.dll, cs2sc.exe, geod.exe, nad2bin.exe, proj.exe with my customs, in my /OSGeo4W/bin folder.

in Qgis: "settings/custom CRS" + "Add new CRS" in the "parameters" i've copied the same string as for other tests as '+proj=mercxx +ellps=intl +units=m +datum=WGS84 +no_defs' (without quotes)

in 'name' field i've wrote...almost everthing my keyboard can write... even the default 'new CSR' the result is always the same when i hit "OK" : "the proj4 definition of 'mercxx' is not valid.

Answer 1

QGIS complains because mercxx is not defined in proj4. Have you defined it, in your custom lib?

Calling proj -lp list all available projections.

user@osgeolive:~$ proj -lp | grep merc
etmerc : Extended Transverse Mercator
merc : Mercator
omerc : Oblique Mercator
somerc : Swiss. Obl. Mercator
gstmerc : Gauss-Schreiber Transverse Mercator (aka Gauss-Laborde Reunion)
tmerc : Transverse Mercator
user@osgeolive:~$

There is no mercxx projection available (in vanilla proj4).

Answer 2

It seems you have not catched all parts of proj. Have you looked into the /OSGEO4W/lib folder as well?

If that does not help, you might have to look up the source code, or ask on the qgis-dev mailing list.