[PROJ] Coordinate transformations between different WGS84 reference frames

[Even Rouault]

Luís,

so you're transforming from WGS 84 (G730) to WGS 84 (G1762). I highly 
doubt that any PROJ version produced anything than a null transformation 
for that, given there's no known (in EPSG database) direct 
transformation between those 2 realizations.

That said, digging a bit, in EPSG, there's :

- a null transformation between WGS 84 (G730) and ITRF92 . Accuracy 0.2m

- a non-null time-dependent Helmert transformation between ITRF92 and 
ITRF2008. Accuracy 0.01 m

- a null transformation between ITRF2008 and WGS 84 (G1762). Accuracy 0.01m

So if you do:

$ echo 20 10 0 2022.6 | cs2cs -d 8  "WGS 84 (G730)" ITRF92 | cs2cs -d 8 
ITRF92 ITRF2008 | cs2cs -d 8 ITRF2008  "WGS 84 (G1762)"

20.00000101    9.99999995 -0.00107558 2022.6

(in practice you can keep omit the first and last cs2cs invokation)

As raised in many threads, PROJ could in theory be enhanced to infer 
that itself, but it would be computationally and programmatically 
complex to do so.

Even

Le 04/08/2022 à 17:13, Luí s Moreira de Sousa via PROJ a écrit :
> Dear all,
>
> This message reports to Proj 8.2.1. I am trying to reproduce an 
> exercise I conducted some years ago with Proj 6 (maybe 7) transforming 
> coordinates between different realisations of the WGS84 ensemble. I am 
> using this formulation:
>
> $ cs2cs EPSG:9053 EPSG:9057
> 20 10
> 20dN 10dE 0.000
>
> My recollection was cs2cs producing visible differences in the order 
> metres. With the current version the output is unchanged transforming 
> between these geodesic CRS. Do I need to use an additional parameter? 
> Or am I missing something else?
>
> Thank you.
>
> -- 
> Luís
>
> _______________________________________________
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> PROJ at lists.osgeo.org
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