[postgis-tickets] [PostGIS] #4932: Possible Bug with geography ST_Intersects / ST_Distance

[PostGIS]

#4932: Possible Bug with geography ST_Intersects / ST_Distance
----------------------+---------------------------
  Reporter:  robe     |      Owner:  pramsey
      Type:  defect   |     Status:  new
  Priority:  medium   |  Milestone:  PostGIS 3.1.3
 Component:  postgis  |    Version:  master
Resolution:           |   Keywords:
----------------------+---------------------------
Description changed by robe:

Old description:

> Nek on PostGIS noted the documentation for geography ST_Intersects is
> wrong.
>
> https://postgis.net/docs/ST_Intersects.html
>
> In the docs it says this should return true
>

> {{{
> SELECT ST_Intersects(
>                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
> 72.4568)'::geography,
>                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
>                 );
> }}}
>
> But it returns false.  I just checked on my PostGIS 3.2 build and it
> indeed returns false.
>
> However ST_Distance returns 0
>
> {{{
> SELECT ST_Distance(
>                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
> 72.4568)'::geography,
>                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
>                 );
> }}}
>
> Even _ST_DistanceTreet returns 0
>

> {{{
> SELECT _ST_DistanceTree(
>                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
> 72.4568)'::geography,
>                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
>                 );
> }}}
>
> However _ST_DistanceUncached returns a small number, so perhaps that is
> what ST_Intersects is using
>

> {{{
> SELECT _ST_DistanceUncached(
>                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
> 72.4568)'::geography,
>                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
>                 );
> }}}
>
> returns - 1.4148932702941524e-09
>
> same answer with PostGIS 3.1.2

New description:

 Nek on PostGIS noted the documentation for geography ST_Intersects is
 wrong.

 https://postgis.net/docs/ST_Intersects.html

 In the docs it says this should return true


 {{{
 SELECT ST_Intersects(
                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
 72.4568)'::geography,
                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
                 );
 }}}

 But it returns false.  I just checked on my PostGIS 3.2 build and it
 indeed returns false.

 However ST_Distance returns 0

 {{{
 SELECT ST_Distance(
                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
 72.4568)'::geography,
                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
                 );
 }}}

 Even _ST_DistanceTree returns 0


 {{{
 SELECT _ST_DistanceTree(
                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
 72.4568)'::geography,
                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
                 );
 }}}

 However _ST_DistanceUncached returns a small number, so perhaps that is
 what ST_Intersects is using


 {{{
 SELECT _ST_DistanceUncached(
                 'SRID=4326;LINESTRING(-43.23456 72.4567,-43.23456
 72.4568)'::geography,
                 'SRID=4326;POINT(-43.23456 72.4567772)'::geography
                 );
 }}}

 returns - 1.4148932702941524e-09

 same answer with PostGIS 3.1.2

--

-- 
Ticket URL: <https://trac.osgeo.org/postgis/ticket/4932#comment:1>
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