[postgis-users] Postgis Raster determine exact hull

[Marcin Mionskowski]

Hi,
Try to reclassify the raster first so that all "non NA" values are equal
(e.g. 1), then do ST_DumpAsPolygons.
Regards,
Marcin

pon., 10 sty 2022 o 21:27 Richard Huesken <richard.huesken at gmail.com>
napisał(a):

> hi,
>
> I'm using postgis 3.1 and I'm looking for the best way to obtain the exact
> hull of a raster (excluding the nodata points). The st_minconvexhull uses
> the MBR of the raster coverage, and is therefore quite fast. The result is
> however not as accurate as I require.
>
> I constructed some sql that uses st_pixelaspolygons and then does a
> st_union. However, My typical raster has 256x256 points, and with several
> 100s of rasters this is quite slow.
>
> Are there more clever (and faster!) ways to get the exact hull of a raster?
>
> Thanks in advance,
>
> Richard.
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