On Fri, 19 Mar 2021 at 07:04, Even Rouault <[email protected]> wrote:
>
> Sebastian,
>
> I can reproduce the 2 error messages you got. There's indeed something in 
> QGIS that tries a terrestrial reprojection and should be fixed, but I don't 
> think this is really critical apart of the annoyance of being spammed about 
> that. Please file a QGIS issue to track this.

There's two parts in particular which cause this warning to be shown,
and indeed make an assumption that lat/lng === EPSG:4326
- The status bar coordinate widget
- The CRS selector "area of use" preview widget

We probably need api for testing "is non earth crs" and "given a
non-earth crs, give me a lat/long crs for the same planetary body" to
resolve these. But as Even has pointed out neither are critical
functionality, and the warning can be ignored.
Nyall


> That said, I managed to do a non-Earth reprojection by adding a custom CRS 
> with the following WKT definition:
>
> GEOGCRS["MARS Geographic",
>
> DATUM["D_MARS",
>
> ELLIPSOID["MARS",3396000,0,
>
> LENGTHUNIT["metre",1,
>
> ID["EPSG",9001]]]],
>
> PRIMEM["Reference meridian",0,
>
> ANGLEUNIT["degree",0.0174532925199433,
>
> ID["EPSG",9122]]],
>
> CS[ellipsoidal,2],
>
> AXIS["longitude",east,
>
> ORDER[1],
>
> ANGLEUNIT["degree",0.0174532925199433,
>
> ID["EPSG",9122]]],
>
> AXIS["latitude",north,
>
> ORDER[2],
>
> ANGLEUNIT["degree",0.0174532925199433,
>
> ID["EPSG",9122]]]]
>
> and selecting it as the project CRS. Using ESRI:104905 (GCS_Mars_2000) seems 
> to also work (I haven't deeply checked but I do get a reprojected raster and 
> geographic coordinates), but you'll get each time the warnings about the 2 
> terrestrial coordinate operations. Hopefully in coming months, I'll be able 
> to ingest the IAU catalog into the PROJ database as well.
>
> Even
>
> Le 18/03/2021 à 21:07, Sebastian Walter a écrit :
>
> Hi,
>
> Since Version 3.X I'm not able to perform transformations on planetary 
> (non-Earth) data (from e.g. Mars or Mercury, example dataset: 
> https://maps.planet.fu-berlin.de/mex4/h1104_0000.ihs.53.tif). The error 
> message is:
>
> No transform is available between SINUSOIDAL MARS and Custom CRS: 
> GEOGCRS["unknown",DATUM["unknown",ELLIPSOID["WGS 8….
> proj_create_operations: Source and target ellipsoid do not belong to the same 
> celestial body
> No transform available between SINUSOIDAL MARS and EPSG:4326
>
> The consequence is that transformations to lat/lon are not possible any more. 
> With the older QGis there was no problem like this. My suspect is the "new" 
> Proj6 database layout, but the above error messages also point to the fact 
> there there is some EPSG:4326 projection hard-coded into Qgis.
>
> Is anybody successfully using Qgis with non-Earth data and proper 
> transformations?
>
> Thanks for any advise...
>
> Sebastian
>
>
>
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