[gdal-dev] Which Proj.4 transforms are available in GDAL?

[Andre Joost]

Am 25.08.2017 um 13:52 schrieb Even Rouault:

>> And also found some that do no agree between GDAL and proj. For
>> example
>>
>> echo 4.897 52.371 | proj +proj=vandg +ellps=WGS84 +units=m
>> 489005.93       6431581.02
>>
>> gdaltransform -s_srs EPSG:4326 -t_srs "+proj=vandg +ellps=WGS84
>> +units=m" 4.897 52.371 488459.293282675 6424391.46347316 0
>
> If you add --debug on, you'll see that GDAL adds a +R_A parameter. I
> haven't dug up into history to know the reason for that. If you add
> +wktext, the original string will be passed unmodified to proj.4
>

https://github.com/OSGeo/proj.4/blob/master/src/PJ_vandg.c only has 
formulas for the spheroid. So it would be better to specify a radius 
directly, instead of an ellipsoid:

echo 4.897 52.371 | proj +proj=vandg +R=6371000
488458.74       6424384.22

gdaltransform -s_srs EPSG:4326 -t_srs "+proj=vandg +R=6371000
4.897 52.371
488458.742715653 6424384.22221862 0

HTH,
André Joost