Some answers:
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Sebastian Gellrich via PROJ kirjoitti 2023-11-03 17:32:
Hello PROJ9 Community,
I have 2 questions about transformations. First of all, I do not know
one hundred percent about transformations.
I use a library I built myself for all possible Android platforms.
Now I am testing the library a little and have encountered the
following problems:
1.
I get a list of all CRS (PJ_TYPE_CRS) with
proj_get_crs_info_list_from_database(...).
For testing purposes, I then create a projection with all CRSs using
proj_create_crs_to_crs(...), which I then normalize with
proj_normalize_for_visualization(...).
My source is always WGS84 (EPSG:4326).
With some projections I get the error "No inverse operation"
(PROJ_ERR_OTHER_NO_INVERSE_OP) after calling
proj_get_crs_info_list_from_database.
What does this mean? Can I somehow create this projection differently?
Example: EPSG:2218
"No inverse operation" means that the projection is just defined
forward. So, you cannot use that projection inverse and the library does
not have any way to calculate inverse. The inverse is not defined. So,
most likely you should remove all such projections from your procedure
or list?
With some CRS of type PJ_TYPE_VERTICAL_CRS I get the error code
"Unknown error (code 4096)".
Here the error code tells me even less what the problem is.
Examples: EPSG:5620
EPSG:6357 (here I also received the log
message "pipeline: Pipeline: Mismatched units between step 3 and 4"
from Proj9)
I don't know what that is. Might be related to previous or similar.
2.
When transforming to type PJ_TYPE_VERTICAL_CRS, the axes seem to be
swapped in the result.
That is much possible in many cases. I assume you just have to live with
it or do some fix in your own coding?!
I used the same WGS84 coordinate for all tests (x=14, y=52, z=100 =>
Germany, Brandenburg).
The transformed coordinates were all x=52 and y=14. Is this
intentional?
Some transformed coordinates also contained only Infinity.
Thanks in advance for your help.
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Regards: Janne
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