[postgis-users] TR: strange behavior of ST_Area(geography)

[IIDA Tetsushi]

thank you, Olivier.

sorry, i forgot to describe my environment.
----------------------------------------------------------------
 PostgreSQL 9.6.3 on x86_64-pc-linux-gnu, compiled by gcc (Debian
4.9.2-10) 4.9.2, 64-bit
 POSTGIS="2.3.2 r15302" GEOS="3.4.2-CAPI-1.8.2 r3921" PROJ="Rel.
4.8.0, 6 March 2012" GDAL="GDAL 1.10.1,
 released 2013/08/26" LIBXML="2.9.1" LIBJSON="0.11.99" RASTER

(docker image "mdillon/postgis")


2017-10-15 21:34 GMT+09:00 Olivier Leprêtre <o.lepretre at gmail.com>:
> 9.6 and
> "POSTGIS="2.3.2 r15302" GEOS="3.6.1-CAPI-1.10.1 r4317" PROJ="Rel. 4.9.1, 04 March 2015" GDAL="GDAL 2.1.3, released 2017/20/01" LIBXML="2.7.8" LIBJSON="0.12" TOPOLOGY RASTER"
>
> -----Message d'origine-----
> De : Olivier Leprêtre [mailto:o.lepretre at gmail.com]
> Envoyé : dimanche 15 octobre 2017 14:33
> À : 'PostGIS Users Discussion'
> Objet : RE: [postgis-users] strange behavior of ST_Area(geography)
>
> I tested your query with 9.6 all tests return true.
>
> Olivier
>
> -----Message d'origine-----
> De : postgis-users [mailto:postgis-users-bounces at lists.osgeo.org] De la part de IIDA Tetsushi Envoyé : dimanche 15 octobre 2017 13:42 À : postgis-users at lists.osgeo.org Objet : [postgis-users] strange behavior of ST_Area(geography)
>
> Hi,
>
> These polygons have the same shape but orientation.
>
> --- my query -----
> WITH poly AS (
>  SELECT
>   ST_SetSRID(ST_GeomFromText(
>    'POLYGON((138.002 37.001, 138.003 37.0010, 138.003 37.0013, 138.002 37.001))'
>    ),4326) g1,
>   ST_SetSRID(ST_GeomFromText(
>    'POLYGON((138.002 37.001, 138.003 37.0013, 138.003 37.0010, 138.002 37.001))'
>    ),4326) g2
> )
> SELECT ST_Equals(g1,g2),
>  ST_Area(g1)                     = ST_Area(g2) AS eq_area,
>  ST_Area(g1::geography)          = ST_Area(g2::geography) AS geog1,
>  ST_Area(g1::geography, false)   = ST_Area(g2::geography, false) AS geog2,
>  ST_Area(g1::geography)          = ST_Area(ST_Reverse(g2)::geography) AS geog3,
>  ST_Area(ST_Transform(g1,32654)) = ST_Area(ST_Transform(g2,32654)) AS geom  FROM poly;
>
> ----- output -----
>
>  st_equals | eq_area | geog1 | geog2 | geog3 | geom
> -----------+---------+-------+-------+-------+------
>  t         | t       | f     | t     | t     | t
>
>
> I expected all these tests return true.
> Is this behavior by spec?
>
> Thanks
>
> --
> hogeman
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-- 
Iida, Tetsushi
飯田　哲士