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Unexpected CRS inequality #3725

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djhoese opened this issue May 11, 2023 · 1 comment · Fixed by #3727
Closed

Unexpected CRS inequality #3725

djhoese opened this issue May 11, 2023 · 1 comment · Fixed by #3727
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@rouault
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@djhoese
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djhoese commented May 11, 2023

Example of problem

#include <proj.h>
#include <stdio.h>

int main(void) {
    PJ_CONTEXT* context = proj_context_create();
    PJ* pj1 = proj_create(
        context,
        "+proj=geos +lon_0=0 +h=35786400 +a=6378137.0 +rf=298.257223563 +units=m +sweep=y +no_defs +type=crs"
    );
    PJ* pj2 = proj_create(
        context,
        "+proj=geos +lon_0=0 +h=35786400 +ellps=WGS84 +units=m +sweep=y +no_defs +type=crs"
    );
    printf("%d\n", proj_is_equivalent_to_with_ctx(
        context, pj1, pj2, PJ_COMP_EQUIVALENT
    ));
    return 0;
}

Problem description

I'm using pyproj and end up comparing two CRS objects. One is created from a and rf parameters taken from a satellite instrument data file (pj1 above). The other is taken from a configuration for the expected/documented/ideal version of this CRS (pj2 above). The instrument/data file is documented as being on an WGS84 ellipsoid (my understanding at least). I expected that these two sets of parameters would be equivalent. I haven't had the time yet to determine if they were in older versions of PROJ.

pyproj4/pyproj#1284

Expected Output

1 meaning the CRSes are equivalent.

Environment Information

  • PROJ version (proj): Rel. 9.1.1, December 1st, 2022
  • Operation System Information: PopOS/Ubuntu

Installation method

  • conda via conda-forge package
@djhoese djhoese added the bug label May 11, 2023
@rouault rouault self-assigned this May 11, 2023
rouault added a commit to rouault/PROJ that referenced this issue May 11, 2023
@rouault
CRS instanciation from PROJ.4 string: set 'Unknown based on XXXX elli…
964d4da 
…psoid' datum name...

...when instanciating from known +a,+rf

and change WGS84 -> WGS 84 and GRS80 -> GRS 1980 to use EPSG names
when building from +ellps=WGS84/GRS80 (fixes OSGeo#3725)

Now we get
```
$ bin/projinfo  "+proj=geos +lon_0=0 +h=35786400 +ellps=WGS84 +units=m +sweep=y +no_defs +type=crs"
PROJ.4 string:
+proj=geos +lon_0=0 +h=35786400 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs +type=crs

WKT2:2019 string:
PROJCRS["unknown",
    BASEGEOGCRS["unknown",
        DATUM["Unknown based on WGS 84 ellipsoid",
            ELLIPSOID["WGS 84",6378137,298.257223563,
                LENGTHUNIT["metre",1],
                ID["EPSG",7030]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8901]]],
    CONVERSION["unknown",
        METHOD["Geostationary Satellite (Sweep Y)"],
        PARAMETER["Longitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Satellite Height",35786400,
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        PARAMETER["False easting",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["(E)",east,
            ORDER[1],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        AXIS["(N)",north,
            ORDER[2],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]]]

$ bin/projinfo  "+proj=geos +lon_0=0 +h=35786400 +a=6378137.0 +rf=298.257223563 +units=m +sweep=y +no_defs +type=crs"
PROJ.4 string:
+proj=geos +lon_0=0 +h=35786400 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs +type=crs

WKT2:2019 string:
PROJCRS["unknown",
    BASEGEOGCRS["unknown",
        DATUM["Unknown based on WGS 84 ellipsoid",
            ELLIPSOID["WGS 84",6378137,298.257223563,
                LENGTHUNIT["metre",1,
                    ID["EPSG",9001]]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8901]]],
    CONVERSION["unknown",
        METHOD["Geostationary Satellite (Sweep Y)"],
        PARAMETER["Longitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Satellite Height",35786400,
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        PARAMETER["False easting",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["(E)",east,
            ORDER[1],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        AXIS["(N)",north,
            ORDER[2],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]]]
```
@rouault rouault mentioned this issue May 11, 2023
Merged
@djhoese
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djhoese commented May 12, 2023

For the record, this seems to work as expected in PROJ 9.0.x but not 9.1.x.

rouault added a commit that referenced this issue May 12, 2023
@rouault @github-actions
CRS instanciation from PROJ.4 string: set 'Unknown based on XXXX elli…
94db72e 
…psoid' datum name...

...when instanciating from known +a,+rf

and change WGS84 -> WGS 84 and GRS80 -> GRS 1980 to use EPSG names
when building from +ellps=WGS84/GRS80 (fixes #3725)

Now we get
```
$ bin/projinfo  "+proj=geos +lon_0=0 +h=35786400 +ellps=WGS84 +units=m +sweep=y +no_defs +type=crs"
PROJ.4 string:
+proj=geos +lon_0=0 +h=35786400 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs +type=crs

WKT2:2019 string:
PROJCRS["unknown",
    BASEGEOGCRS["unknown",
        DATUM["Unknown based on WGS 84 ellipsoid",
            ELLIPSOID["WGS 84",6378137,298.257223563,
                LENGTHUNIT["metre",1],
                ID["EPSG",7030]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8901]]],
    CONVERSION["unknown",
        METHOD["Geostationary Satellite (Sweep Y)"],
        PARAMETER["Longitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Satellite Height",35786400,
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        PARAMETER["False easting",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["(E)",east,
            ORDER[1],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        AXIS["(N)",north,
            ORDER[2],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]]]

$ bin/projinfo  "+proj=geos +lon_0=0 +h=35786400 +a=6378137.0 +rf=298.257223563 +units=m +sweep=y +no_defs +type=crs"
PROJ.4 string:
+proj=geos +lon_0=0 +h=35786400 +x_0=0 +y_0=0 +ellps=WGS84 +units=m +no_defs +type=crs

WKT2:2019 string:
PROJCRS["unknown",
    BASEGEOGCRS["unknown",
        DATUM["Unknown based on WGS 84 ellipsoid",
            ELLIPSOID["WGS 84",6378137,298.257223563,
                LENGTHUNIT["metre",1,
                    ID["EPSG",9001]]]],
        PRIMEM["Greenwich",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8901]]],
    CONVERSION["unknown",
        METHOD["Geostationary Satellite (Sweep Y)"],
        PARAMETER["Longitude of natural origin",0,
            ANGLEUNIT["degree",0.0174532925199433],
            ID["EPSG",8802]],
        PARAMETER["Satellite Height",35786400,
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        PARAMETER["False easting",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8806]],
        PARAMETER["False northing",0,
            LENGTHUNIT["metre",1],
            ID["EPSG",8807]]],
    CS[Cartesian,2],
        AXIS["(E)",east,
            ORDER[1],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]],
        AXIS["(N)",north,
            ORDER[2],
            LENGTHUNIT["metre",1,
                ID["EPSG",9001]]]]
```
@djhoese djhoese mentioned this issue Sep 1, 2023
Closed
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