[PROJ] ballpark transformation ITRF2014 -> CH1903+

[Even Rouault]

Le 29/04/2021 à 15:22, Greg Troxel a écrit :
> Javier Jimenez Shaw <j1 at jimenezshaw.com> writes:
>
>> I could not expect that such transformation was not published.
>> Now I see that WGS84(G1762) to ETRS89 goes through WGS84, with an accuracy
>> of 3m. Looks like Europe is isolated from the World (in a datum accurate
>> transformation sense ;)
> It seems to be quite published (by an author whose name will be quite
> familiar to followers of ITRF).  It seems that it is merely not
> expressed in the EPSG database.
>
>    http://etrs89.ensg.ign.fr/pub/EUREF-TN-1.pdf

Actually the data from table 1, 2 and 3 of this paper is in EPSG. But 
you need to invoke the precise ETRFxx frame, not just the generic ETRS89

$ projinfo -s ETRF89 -t ITRF89 -o PROJ -q
+proj=pipeline
   +step +proj=axisswap +order=2,1
   +step +proj=unitconvert +xy_in=deg +xy_out=rad
   +step +proj=cart +ellps=GRS80
   +step +inv +proj=helmert +x=0 +y=0 +z=0 +rx=0 +ry=0 +rz=0 +s=0 +dx=0 
+dy=0
         +dz=0 +drx=0.00011 +dry=0.00057 +drz=-0.00071 +ds=0 +t_epoch=1989
         +convention=position_vector
   +step +inv +proj=cart +ellps=GRS80
   +step +proj=unitconvert +xy_in=rad +xy_out=deg
   +step +proj=axisswap +order=2,1

$ projinfo -s ETRF2014 -t ITRF2014 -o PROJ -q
+proj=pipeline
   +step +proj=axisswap +order=2,1
   +step +proj=unitconvert +xy_in=deg +xy_out=rad
   +step +proj=cart +ellps=GRS80
   +step +inv +proj=helmert +x=0 +y=0 +z=0 +rx=0.001785 +ry=0.011151 
+rz=-0.01617
         +s=0 +dx=0 +dy=0 +dz=0 +drx=8.5e-05 +dry=0.000531 +drz=-0.00077 
+ds=0
         +t_epoch=2010 +convention=position_vector
   +step +inv +proj=cart +ellps=GRS80
   +step +proj=unitconvert +xy_in=rad +xy_out=deg
   +step +proj=axisswap +order=2,1

$ projinfo -s ETRF89 -t ITRF2014 -o PROJ -q
+proj=pipeline
   +step +proj=axisswap +order=2,1
   +step +proj=unitconvert +xy_in=deg +xy_out=rad
   +step +proj=cart +ellps=GRS80
   +step +inv +proj=helmert +x=0 +y=0 +z=0 +rx=0 +ry=0 +rz=0 +s=0 +dx=0 
+dy=0
         +dz=0 +drx=0.00011 +dry=0.00057 +drz=-0.00071 +ds=0 +t_epoch=1989
         +convention=position_vector
   +step +proj=helmert +x=-0.0304 +y=-0.0355 +z=0.1308 +rx=0 +ry=0 
+rz=-0.00026
         +s=-0.00819 +dx=-0.0001 +dy=0.0005 +dz=0.0033 +drx=0 +dry=0 
+drz=-2e-05
         +ds=-0.00012 +t_epoch=2010 +convention=position_vector
   +step +inv +proj=cart +ellps=GRS80
   +step +proj=unitconvert +xy_in=rad +xy_out=deg
   +step +proj=axisswap +order=2,1


>
> Also there's the minor issue that ETRS89 is a system not a frame and
> there are many ETRFnn and ETRFnnnn frames.  So ETRS89 appears to be one
> of those pesky datum ensembles, from a pedantic view.
>
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