[PROJ] Help needed for a cs2cs pipeline with shift grids

[Nicolas Bellaiche]

Hi there, 

I try to make a conversion using shiftgrids from IGNF: NTFP to IGNF:ETRS89LCC. By default, it seems that it uses the helmert approximation between the 2 crs and i cannot figure out how to use the grid fr_ign_ntf_r93. 

So far i've found how to create a pipeline that works with cct, but i'd like to have a code that represents the crs and be able to go to different destination crs with the cs2cs application. Any idea? 

(helmert approx + no geoid with the standard codes) 


echo 0 56 0 | ./cs2cs + from IGNF:NTFP +to IGNF:ETRS89LCC 

result : 3474788.21 2655358.23 0.00 




(correct pipeline) 

echo 0 56.000000 0 | PROJ_DEBUG=3 ./cct +proj=pipeline +step +proj=unitconvert +xy_in=grad +xy_out=rad +step +inv +proj=longlat +ellps=clrk80ign +pm=paris +step +proj=hgridshift +grids=fr_ign_ntf_r93.tif +step +inv +proj=vgridshift +grids=RAF09.gtx +step +proj=lcc +lat_0=52 +lon_0=10 +lat_1=35 +lat_2=65 +x_0=4000000 +y_0=2800000 +ellps=GRS80 




result : 3474789.9972 2655359.2908 43.6421 inf 




reference from THE official IGN/SGN dataset: 

3474789.997 2655359.291 43.642 







Thanks a lot for your help, 




Nicolas Bellaiche 

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