ST_Area bug?

[Mike Taves]

Note this is a tricky polygon in Antarctica:
http://www.gcmap.com/mapui?P=79.736894381S+0.780387531W-79.736894381S+170.375361283E-79.692508368S+170.375361283E-79.692508368S+0.780387531W-79.736894381S+0.780387531W&MS=wls&DU=km

The area is 899078042.2 m2 as verified using:
https://geographiclib.sourceforge.io/cgi-bin/Planimeter?type=polygon&rhumb=geodesic&radius=6378137&flattening=1%2F298.257223563&input=-79.736894381+-0.780387531%0D%0A-79.736894381+170.375361283%0D%0A-79.692508368+170.375361283%0D%0A-79.692508368+-0.780387531%0D%0A-79.736894381+-0.780387531&option=Submit

PostGIS uses GeoGraphicLib's method
(https://doi.org/10.1007/s00190-012-0578-z) which has high accuracy.
The bug is likely with other resources.


On Wed, 26 Mar 2025 at 05:58, Alexander Trufanov <trufanovan at gmail.com> wrote:
>
> Hello,
>
> I've a following area calculation:
>
> select ST_Area(
> ST_GeometryFromText('POLYGON ((-0.780387531 -79.736894381,
> 170.375361283 -79.736894381,
> 170.375361283 -79.692508368,
> -0.780387531 -79.692508368,
> -0.780387531 -79.736894381))', 4326)::geography) /1000000
>
> which returns ~900 km^2
>
> while ST_Perimeter() for the same geography is ~4600km
> and If I open ST_AsGeoJson() of this geometry in google earth pro and some websites I'm getting ~ 16700 km^2.
> It seems it's a correct result and ST_Area() result is wrong.
>
> Is this a known problem?
>
> My versions:
> PostgreSQL 15.10 (Debian 15.10-astra.se1) on x86_64-pc-linux-gnu, compiled by gcc (Astra 12.2.0-14.astra3+b1) 12.2.0, 64-bit
> POSTGIS="3.3.2 68f4434" [EXTENSION] PGSQL="150" GEOS="3.11.1-CAPI-1.17.1" PROJ="9.1.1" GDAL="GDAL 3.6.2, released 2023/01/02" LIBXML="2.9.14" LIBJSON="0.16" LIBPROTOBUF="1.4.1" WAGYU="0.5.0 (Internal)" RASTER
>
> --
> With best regards,
> Truf