[PROJ] Transforming between ITRF realizations

[Markus Metz]

On Fri, May 3, 2019 at 8:58 PM Even Rouault <even.rouault at spatialys.com>
wrote:
>
> On vendredi 3 mai 2019 13:01:01 CEST Alan Snow wrote:
[...]
>
> The +init=ITRF2000:ITRF93 definition uses a +proj=helmert operation which
> operates in the cartesian/geocentric coordinate space. So you need to
convert
> from geographic to geocentric coordinates first.
>
> $ echo "-117.61748, 59.4967, 329.396" | src/cct -d 7 +proj=pipeline \
>   +step +proj=unitconvert +xy_in=deg +xy_out=rad \
>   +step +proj=cart +ellps=GRS80 \
>   +step +init=ITRF2000:ITRF93 \
>   +step +inv +proj=cart +ellps=GRS80 \
>   +step +proj=unitconvert +xy_in=rad +xy_out=deg

that means we (developers) need to check with proj_angular_input() if such
a unit conversion is needed? AFAIU, units are now degrees as in EPSG:4326,
and in this case a conversion to radians is no longer required, as in
proj-4.

Markus M
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