Bonjour M. Rouault, 




Voilà ce que j'obtiens: 




PROJ9: 




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







pj_open_lib(proj.ini): call 
fopen(/Users/nbellaiche/dev/sd-externs/macosx-clang/proj-9.1.1/nad/proj.ini) - 
succeeded 

pj_open_lib(proj.db): call 
fopen(/Users/nbellaiche/dev/sd-externs/macosx-clang/proj-9.1.1/nad/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 







Release % echo 652760.73700000 7033791.24300000 43.64200000 | cs2cs 
+init=IGNF:LAMB93 +to +init=IGNF:RGF93 

4070355.05 166080.07 4891332.24 







Release % echo $PROJ_DATA 

/Users/nbellaiche/dev/sd-externs/macosx-clang/proj-9.1.1/nad 






Release % echo $PROJ_LIB 

/Users/nbellaiche/dev/sd-externs/macosx-clang/proj-9.1.1/nad 







je ne vois pas de différence. Je n'ai pas le début d'une idée de comment 
identifier le problème... 




N. 







De: "Even Rouault" <[email protected]> 
À: "proj" <[email protected]> 
Envoyé: Vendredi 26 Mai 2023 21:50:27 
Objet: Re: [PROJ] Migrating to PROJ-9 



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 : 

BQ_BEGIN

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 

echo 652760.73700000 7033791.24300000 43 .64200000 | cs2cs +init=IGNF:LAMB93 
+to +init=IGNF:RGF93: 

4070327.25 166078.93 4891298.61 




PROJ7 or PROJ9 

echo 652760.73700000 7033791.24300000 43 .64200000 | cs2cs +init=IGNF:LAMB93 
+to +init=IGNF:RGF93: 

4070355.05 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 

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free, but my time generally not. 

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