#25498: PostGIS Distance lookups use ST_Distance_Sphere() and not ST_Distance()
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Reporter: iambibhas | Owner: nobody
Type: Bug | Status: new
Component: Documentation | Version: master
Severity: Normal | Resolution:
Keywords: | Triage Stage: Unreviewed
Has patch: 1 | Needs documentation: 0
Needs tests: 0 | Patch needs improvement: 0
Easy pickings: 0 | UI/UX: 0
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Description changed by iambibhas:
Old description:
> Currently
> [https://docs.djangoproject.com/en/1.8/ref/contrib/gis/geoquerysets
> /#distance-gt the doc says] that PostGIS uses `ST_Distance()` for
> distance lookups like `distance_gte` etc. But actually
> `ST_Distance_Sphere()` is used. We need to fix that on the doc.
>
> The doc also says in the beginning -
>
> {{{
>
> ... an optional third element, 'spheroid', may be included to tell
> GeoDjango to use the more accurate spheroid distance calculation
> functions on fields with a geodetic coordinate system (e.g.,
> ST_Distance_Spheroid would be used instead of ST_Distance_Sphere).
>
> }}}
>
> But then `ST_Distance_Sphere` is not mentioned anywhere else.
>
> Here is what currently is happening -
>
> {{{
> current_localities = Locality.objects.filter(centroid__distance_lte=(pnt,
> 1000))
> }}}
>
> results in -
>
> {{{
> (0.005) SELECT "map_locality"."id", "map_locality"."name",
> "map_locality"."slug", "map_locality"."centroid", "map_locality"."radius"
> FROM "map_locality" WHERE ST_Distance_Sphere("map_locality"."centroid",
> ST_GeomFromEWKB('\x0101000020e6100000865ad3bce3685340e9b7af03e7ec2940'::bytea))
> <= 1000 LIMIT 21;
> args=(<django.contrib.gis.db.backends.postgis.adapter.PostGISAdapter
> object at 0x7fdcc9d320d0>, 1000)
> }}}
>
> Attaching a patch with the issue. I can send a PR.
New description:
Currently
[https://docs.djangoproject.com/en/1.8/ref/contrib/gis/geoquerysets
/#distance-gt the doc says] that PostGIS uses `ST_Distance()` for distance
lookups like `distance_gte` etc. But actually `ST_Distance_Sphere()` is
used. We need to fix that on the doc.
The doc also says in the beginning -
... an optional third element, 'spheroid', may be included to tell
GeoDjango to use the more accurate spheroid distance calculation functions
on fields with a geodetic coordinate system (e.g., `ST_Distance_Spheroid`
would be used instead of `ST_Distance_Sphere`).
But then `ST_Distance_Sphere` is not mentioned anywhere else.
Here is what currently is happening -
{{{
current_localities = Locality.objects.filter(centroid__distance_lte=(pnt,
1000))
}}}
results in -
{{{
(0.005) SELECT "map_locality"."id", "map_locality"."name",
"map_locality"."slug", "map_locality"."centroid", "map_locality"."radius"
FROM "map_locality" WHERE ST_Distance_Sphere("map_locality"."centroid",
ST_GeomFromEWKB('\x0101000020e6100000865ad3bce3685340e9b7af03e7ec2940'::bytea))
<= 1000 LIMIT 21;
args=(<django.contrib.gis.db.backends.postgis.adapter.PostGISAdapter
object at 0x7fdcc9d320d0>, 1000)
}}}
Attaching a patch with the issue. I can send a PR.
--
--
Ticket URL: <https://code.djangoproject.com/ticket/25498#comment:2>
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