[PROJ] Migrating to PROJ-9

[Even Rouault]

Ah, and you should avoid using the "+init=" prefix. This is a deprecated 
legacy syntax that doesn't enforce axis order of the CRS definition 
(without practical consequence for IGNF: CRS since they use "GIS 
friendly" axis order)

To help debugging this, please provide the output of:

PROJ_DEBUG=3 projinfo -s IGNF:LAMB93 -t IGNF:RGF93 -o PROJ

On my system I get:

pj_open_lib(proj.ini): call 
fopen(/home/even/proj/install-proj-master/share/proj/proj.ini) - succeeded
pj_open_lib(proj.db): call 
fopen(/home/even/proj/install-proj-master/share/proj/proj.db) - succeeded
Candidate operations found: 1
-------------------------------------
Operation No. 1:

unknown id, Inverse of LAMBERT-93 + Conversion from RGF93 geographiques 
(dms) to RGF93 cartesiennes geocentriques, 0 m, World

PROJ string:
+proj=pipeline
   +step +inv +proj=lcc +lat_0=46.5 +lon_0=3 +lat_1=44 +lat_2=49 +x_0=700000
         +y_0=6600000 +ellps=GRS80
   +step +proj=cart +ellps=GRS80

Le 26/05/2023 à 21:46, Even Rouault a écrit :
>
> Hi,
>
> I get the expected 4070327.25 166078.93 4891298.61 result with proj 
> 6.0.0, 7.2.1, 9.2.0 and master
>
> There's no grid involved in this operation, just inverse LCC 
> projection on the RGF93 datum
>
> I also tried to reproduce your issue if the PROJ < 6 IGNF file is 
> found in the PROJ resource path(s) (non nominal situation - this file 
> is not needed any more, and will generally lead to suboptimal results. 
> Its content is included in the proj.db file), but even with that I get 
> the expected result. So no idea why you get wrong results
>
> Even
>
>
> Le 26/05/2023 à 20:54, Nicolas Bellaiche a écrit :
>> Hi all,
>>
>> I'm migrating my C++ code from PROJ4 to PROJ9 and I meet a worrying 
>> issue with the computation. Some of my regress tests don't pass so 
>> I've tested with cs2cs and gets the same difference:
>>
>> PROJ4
>>
>> echo652760.73700000 <callto:652760.73700000>7033791.24300000 43 
>> <callto:7033791.24300000 43>.64200000 | cs2cs +init=IGNF:LAMB93 +to 
>> +init=IGNF:RGF93:
>>
>> 4070327.25166078.93 4891298.61 <callto:166078.93 4891298.61>
>>
>>
>> PROJ7 or PROJ9
>>
>> echo652760.73700000 <callto:652760.73700000>7033791.24300000 43 
>> <callto:7033791.24300000 43>.64200000 | cs2cs +init=IGNF:LAMB93 +to 
>> +init=IGNF:RGF93:
>>
>> 4070355.05166080.07 4891332.24 <callto:166080.07 4891332.24>
>>
>>
>>
>>
>> I suspect that PROJ7 and PROJ9 don't read properly the geoid file but 
>> I'm not sure. Someone can help me tracking and fixing this problem?
>>
>> Thanks,
>>
>> Nicolas Bellaiche
>> Institut Géographique National France
>>
>> _______________________________________________
>> PROJ mailing list
>> PROJ at lists.osgeo.org
>> https://lists.osgeo.org/mailman/listinfo/proj
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>
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My software is free, but my time generally not.
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