[postgis-users] Generating areas from point datasets with PostGIS

[pcreso at pcreso.com]

Hi,

Any comments or advice appreciated...

I have a table (155m points) of circumpolar depth points.

>From this I want to use POstGIS to generate polygons based on depths.

There are about 700,000 points in the Ross Sea region, each has a depth (or altitude) associated with it. The points are 1/2nm apart (GEBCO 2008 data)

I figure the following approach will work to generate reasonable polygons for areas in the Ross Sea shallower than 550m:

select astext(geomunion(envelope(buffer(geom,1.0/230.0))))
                from srtm_ant
                where depth <0
                  and depth >-500
                  and geom && setsrid(geometryfromtext('POLYGON((155 -80,155 -60,200 -60,200 -80,155 -80))'),4326);


The && WKT coords define the Ross Sea region, 1/2nm is 1/120 degree so a buffer of 1/230 degree should ensure the envelopes of the buffered points all overlap.


Does anyone have any suggestions/advice regarding this?

Better or faster approaches, etc.


Thanks,

  Brent Wood