[postgis-tickets] [PostGIS] #4215: Drop usage of GDALPolygonize in DT_DumpAsPolygons

[PostGIS]

#4215: Drop usage of GDALPolygonize in DT_DumpAsPolygons
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  Reporter:  komzpa  |      Owner:  Bborie Park
      Type:  defect  |     Status:  new
  Priority:  medium  |  Milestone:  PostGIS 2.4.6
 Component:  raster  |    Version:  2.4.x
Resolution:          |   Keywords:
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Description changed by komzpa:

Old description:

> http://brian-mcgill-4.ums.maine.edu/postgis_zonal.pdf :
>
> {{{
> However this function is
> inadequate for the current purpose – it merges pixels with the same value
> into larger polygons. In
> principle this should still be acceptable but the actual implementation
> (in a poorly documented
> “feature”) does this by converting every value to an integer. So pixels
> with a temperature of
> 13.49 and 12.51 are merged incorrectly (and the value stored is 13 which
> is also incorrect) }}}
>
> Looking at code we have branching on whether GDAL>F<Polygonize is
> available, and that looks hardcoded to "no". We're supporting GDAL 1.10+
> and GDALFpolygonize is available since 1.9.0, so branching can be
> removed.

New description:

 http://brian-mcgill-4.ums.maine.edu/postgis_zonal.pdf :

 {{{
 However this function is
 inadequate for the current purpose – it merges pixels with the same value
 into larger polygons. In
 principle this should still be acceptable but the actual implementation
 (in a poorly documented
 “feature”) does this by converting every value to an integer. So pixels
 with a temperature of
 13.49 and 12.51 are merged incorrectly (and the value stored is 13 which
 is also incorrect)
 }}}

 Looking at code we have branching on whether GDAL>F<Polygonize is
 available, and that looks hardcoded to "no". We're supporting GDAL 1.10+
 and GDALFpolygonize is available since 1.9.0, so branching can be removed.

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Ticket URL: <https://trac.osgeo.org/postgis/ticket/4215#comment:1>
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