[PROJ] Transformations in ITRF2020

[Javier Jimenez Shaw]

Aren't they using CHTRS95 ?
https://epsg.org/crs_4933/CHTRS95.html

On Wed, 18 Sept 2024 at 11:53, Lesparre, Jochem <Jochem.Lesparre at kadaster.nl>
wrote:

>
>
> > Looking at the pipelines, the steps would be ITRF2020 -> ETRF2020 ->
> ETRS89 -> CH1903+
>
>
>
> I am pretty sure Switzerland uses ETRF2000 as ETRS89 realisation, not
> ETRF2020. So, the correct transformation would be:
>
>
>
> ITRF2020 -> ETRF2000 -> ETRS89 -> CH1903+
>
>
>
> The difference between ETRF2000 and ETRF2020 is about 7 cm. ETRF2000 is
> recommended for use by national mapping agencies.
>
>
>
> Jochem
>
>
>
>
>
> *From:* PROJ <proj-bounces at lists.osgeo.org> *On Behalf Of *Javier Jimenez
> Shaw via PROJ
> *Sent:* dinsdag 27 augustus 2024 19:30
> *To:* proj <PROJ at lists.osgeo.org>
> *Subject:* [PROJ] Transformations in ITRF2020
>
>
>
> Hi
>
>
>
> I am now facing transformations with ITRF2020 with time(yes, because
> Skylark, but I guess more NTRIPs are going to do (or already doing) the
> same)
>
>
>
> The point is when the destination CRS does not have a direct
> transformation from ITRF2020 (or almost).
>
>
>
> For instance, EPSG:4150, CH1903+ (the geographic of LV95, in Switzerland)
> is only connected to ETRS89. See that CH1903+ is in the European tectonic
> plate, as ETRS89
>
>
>
> A direct transformation is completely ballpark
>
>
>
> echo 42 6 0 2024.6 | ./cs2cs EPSG:9989 EPSG:4150 -d 9 --3d
> 42.000000000 6.000000000 0.000000000 2024.6
>
>
>
> However, from ITRF2020 to ETRS89 there is some change due to the time (the
> European plate moving at 2.5 cm/a since 2015):
>
> echo 42 6 0 2024.6 | ./cs2cs EPSG:9989 EPSG:4937 -d 9 --3d
> 41.999994981 5.999991317 -0.001861237 2024.6
>
>
>
> and from ETRS89 to CH1903+ due to the datum offset:
> echo 42 6 0 2024.6 | ./cs2cs EPSG:4937 EPSG:4150 -d 9 --3d
> 42.000742733 6.000670188 -60.682799297 2024.6
>
>
>
> Looking at the pipelines, the steps would be ITRF2020 -> ETRF2020 ->
> ETRS89 -> CH1903+
>
> (btw, only since PROJ 9.4.1, when ETRF2020 was added)
>
>
>
> I understand that the only way to get the proper transformation is
> chaining these two manually. Via ETRS89 ... because I know it. Right?
>
>
>
> Well, the future does not look so promising to me: in EPSG I only see
> transformations from ITRF2020 to ETRF family, NAD83(2011) family and
> NAD83(CSRS)v8. That is Europe, USA and Canada. That's all, folks.
>
>
>
> Thanks,
>
> .___ ._ ..._ .. . ._.  .___ .. __ . _. . __..  ... .... ._ .__
>
> Javier Jimenez Shaw
>
> Mercator str 42.
>
> Null-Island
>
>
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