[PostGIS] #5671: Bug in ST_Area function with use_spheroid=false
PostGIS
trac at osgeo.org
Mon Feb 19 06:13:54 PST 2024
#5671: Bug in ST_Area function with use_spheroid=false
----------------------+-----------------------------------
Reporter: azakh | Owner: pramsey
Type: defect | Status: new
Priority: medium | Milestone:
Component: postgis | Version: 3.3.x
Resolution: | Keywords: ST_Area, use_spheroid
----------------------+-----------------------------------
Description changed by azakh:
Old description:
> ST_Area fails to calculate the area of the geography polygon with one
> inner ring, with `use_spheroid=false`:
>
> {{{
> SELECT ST_Area(
> 'POLYGON(
> (
> -111.772 33.307,
> -111.772 33.304,
> -111.783 33.304,
> -111.783 33.307,
> -111.772 33.307
> ),
> (
> -111.781442 33.304825,
> -111.776964 33.3048,
> -111.773047 33.304778,
> -111.773177 33.306408,
> -111.781442 33.304825
> )
> )
> '::geography, false);
> }}}
>
> The result is:
> {{{
> ERROR: lwgeom_area_spher(oid) returned area < 0.0
> }}}
>
> `use_spheroid=true` version works and gives `270218.45392724127`, but I
> would expect the on-the-sphere version also to work.
>
> The polygon seems to be correct, though it has almost flat angle at the
> `(-111.776964 33.3048)` vertex. Let's call the vertex **X**.
>
> If **X** is removed then `ST_Area` is `270337.25718276866`.
>
> If we retain **X** but make a cyclic shift of the inner ring: **AXBCA**
> => **XBCAX**, then the function succeeds but gives `91737.85992092389`
> which is quite different from the correct value.
>
> Let's give small amends to the **X** latitude with **AXBCA** vertex
> order: \\ **X** => `(-111.776964 (33.3048 + amend))`.
>
> {{{
> Amend | ST_Area
> -------------------------------
> -1.0e-05 | 269904.2853637372
> -1.0e-06 | 270298.26808849035
> -1.0e-07 | 270628.6930016738
> -1.0e-08 | 269541.18027120724
> -1.0e-09 | 315257.7589488026
> -1.0e-10 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
> -1.0e-11 | 262120.12981526955
> -1.0e-12 | 41142.8857341336
> -1.0e-13 | 144916.06439020386
> -1.0e-14 | 41142.8857341336
> -1.0e-15 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
> 1.0e-15 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
> 1.0e-14 | 159848.6351422007
> 1.5e-14 | 113982.3188750676
> 5.0e-14 | 243067.1526449226
> 7.5e-14 | 95027.49039558775
> 1.0e-13 | 41142.8857341336
> 5.0e-13 | 159848.59909125822
> 7.5e-13 | 320241.96397413884
> 1.0e-10 | 131857.65595877985
> 2.5e-10 | 185479.48530059034
> 1.0e-12 | 91867.01242231275
> 2.5e-12 | 165036.9786292576
> 5.0e-12 | 204984.361034764
> 7.5e-12 | 35520.7773073109
> 1.0e-11 | 116531.9857301203
> 2.5e-11 | 64257.524312080175
> 5.0e-11 | 253059.59064874944
> 5.0e-10 | 261657.84858001219
> 7.5e-10 | 260622.88009819158
> 1.0e-09 | 265687.2263686325
> 1.0e-08 | 270029.18385391496
> 1.0e-07 | 270240.35224941676
> 1.0e-06 | 270325.2882698695
> 1.0e-05 | 270771.5448612002
> }}}
>
> Monotonous area growth is expected but oscillating behaviour alternating
> with ERRORs is observed.
New description:
ST_Area fails to calculate the area of the geography polygon with one
inner ring, with `use_spheroid=false`:
{{{
SELECT ST_Area(
'POLYGON(
(
-111.772 33.307,
-111.772 33.304,
-111.783 33.304,
-111.783 33.307,
-111.772 33.307
),
(
-111.781442 33.304825,
-111.776964 33.3048,
-111.773047 33.304778,
-111.773177 33.306408,
-111.781442 33.304825
)
)
'::geography, false);
}}}
The result is:
{{{
ERROR: lwgeom_area_spher(oid) returned area < 0.0
}}}
`use_spheroid=true` version works and gives `270218.45392724127`, but I
would expect the on-the-sphere version also to work.
The polygon seems to be correct, though it has almost flat angle at the
`(-111.776964 33.3048)` vertex. Let's call the vertex **X**.
If **X** is removed then `ST_Area` is `270337.25718276866`.
If we retain **X** but make a cyclic shift of the inner ring: **AXBCA** =>
**XBCAX**, then the function succeeds but gives `91737.85992092389` which
is quite different from the correct value.
Let's give small amends to the **X** latitude with **AXBCA** vertex order:
\\ **X** => `(-111.776964 (33.3048 + amend))`.
{{{
Amend | ST_Area
-------------------------------
-1.0e-05 | 269904.2853637372
-1.0e-06 | 270298.26808849035
-1.0e-07 | 270628.6930016738
-1.0e-08 | 269541.18027120724
-1.0e-09 | 315257.7589488026
-1.0e-10 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
-1.0e-11 | 262120.12981526955
-1.0e-12 | 41142.8857341336
-1.0e-13 | 144916.06439020386
-1.0e-14 | 41142.8857341336
-1.0e-15 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
0.0e000 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
1.0e-15 | ERROR: lwgeom_area_spher(oid) returned area < 0.0
1.0e-14 | 159848.6351422007
1.5e-14 | 113982.3188750676
5.0e-14 | 243067.1526449226
7.5e-14 | 95027.49039558775
1.0e-13 | 41142.8857341336
5.0e-13 | 159848.59909125822
7.5e-13 | 320241.96397413884
1.0e-12 | 91867.01242231275
2.5e-12 | 165036.9786292576
5.0e-12 | 204984.361034764
7.5e-12 | 35520.7773073109
1.0e-11 | 116531.9857301203
2.5e-11 | 64257.524312080175
5.0e-11 | 253059.59064874944
1.0e-10 | 131857.65595877985
5.0e-10 | 261657.88463095468
1.0e-09 | 265687.2263686325
1.0e-08 | 270029.18385391496
1.0e-07 | 270240.35224941676
1.0e-06 | 270325.2882698695
1.0e-05 | 270771.5448612002
}}}
Monotonous area growth is expected but oscillating behaviour alternating
with ERRORs is observed.
--
--
Ticket URL: <https://trac.osgeo.org/postgis/ticket/5671#comment:1>
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