ST_Area returns negative values

[chaosmail]

Hi guys,

When computing the Area of a single Polygon as MultiPolygon, the resulting area is negative.

SELECT
  ST_Area(ST_MultiPolygon(array(0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0)))
FROM src LIMIT 1;

>OK
> -1.0
> Time taken: 3.583 seconds, Fetched: 1 row(s)

When using a Polygon, it is working properly.

SELECT
  ST_Area(ST_Polygon(0.0, 0.0, 1.0, 0.0, 1.0, 1.0, 0.0, 1.0))
FROM src LIMIT 1;
> OK
> 1.0
> Time taken: 0.845 seconds, Fetched: 1 row(s)

Best, Christoph

[randallwhitman]

Thanks for reporting this - will need looking into. Also, I have reproduced the reported output.

[randallwhitman]

Contrast:

select ST_Area(ST_MultiPolygon('multipolygon(((0.0 0.0, 1.0 0.0, 1.0 1.0, 0.0 1.0, 0.0 0.0)))')); 1.0 select ST_Area(ST_MultiPolygon(array(0.0, 0.0, 0.0, 1.0, 1.0, 1.0, 1.0, 0.0))); 1.0

[randallwhitman]

In ST_Polygon, we obviate ordering/orientation issues constructing from number pairs, by generating WKT. We could do the same in ST_MultiPolygon. comments @climbage ?

[climbage]

Seems reasonable

[randallwhitman]

Also, ST_MultiPolygon erroneously sets y=x for the first point listed.

select ST_AsText(ST_MultiPolygon(array(0.0, 1.0, 1.0, 1.0, 1.0, 0.0))); MULTIPOLYGON (((0 0, 1 0, 1 1, 0 0)))