[postgis-devel] wktraster ST_ConvexHull

Jorge Arevalo jorgearevalo at gis4free.org
Wed Apr 7 06:43:47 PDT 2010


Hello,

This is a "high-level" conversation. Consider my message as a little
fork :-). I'd like to remark 2 points:

On Tue, Apr 6, 2010 at 6:54 PM, Pierre Racine
<Pierre.Racine at sbf.ulaval.ca> wrote:
>
> One problem I see is that people see the result of ST_Dump as simple polygons when the result of ST_AsPolygon is not necessarily simple polygons. You get simple polygons only when you add the 'CONTIGUOUS' keyword to the function (ST_AsPolygon(raster, integer, 'CONTIGUOUS')).
>

Then, the 'CONTIGUOUS' keyword is used only when you want single
polygons in the output geometry (I suppose this terminology, with
CONTIGUOUS word, comes from any GIS field...). I think this could be a
problem, because GDALPolygonize allways generates standard WKB
polygons. I've used this function for st_aswktpolygon. So, the
function always works as if 'CONTIGUOUS' option is specified. Should
we codify our own polygonize function? We had this discussion some
months ago...


>>Getting to names -- ST_AsWKTPolygon should not start with an ST_ if it is
>>not intended for end user use.
>
> Jorge, could we rename ST_AsWKTPolygon to RasterAsWKTPolygon?
>

Of course. We should avoid "ST" in functions not intended for end-user
use. But, do we all agree on that name? Seems Regina prefer a name
like "ExtractAsWKTPolygons". I personally like this name. Or
"RasterAsWKTPolygons"...


Best regards,
Jorge

> Pierre
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