[postgis-users] spatial indices on two geometry or rast columns

[Vishal Mehta]

Hi all,

I have some vector layers in  a postgis database in EPSG 4326. Spatial indices have been built using GIST on the same (EPSG 4326) geometries on a geometry column called geom.

I'd like to transform these layers to UTM (EPSG 32643). I was thinking of creating a new geometry column for each table and

ALTER TABLE wards ADD column geom_utm geometry;

UPDATE wards SET geom_utm = ST_TRANSFORM(geom,32643);

Should I, (and can I) create another gist index on the transformed geometry?

The same qn applies on a raster table I have called srtm_table - should I and can I add

-          a new 'rast' column called rast_utm with transformed SRID in similar fashion above, and then add a gist index on the rast_utm column?

CREATE INDEX "srtm_table_rast_gist_idx" ON "public"."srtm_table" USING GIST (st_convexhull(rast_utm));

Thanks,
Vishal

Vishal K. Mehta<http://sei-us.org/about/staff_person/19>, Ph.D.
Staff Scientist,
Stockholm Environment Institute-US
400 F St, Davis, CA 95616
http://sei-us.org/



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