13

I have a tiff raster in my PostGIS 2.0 database. I want to get the value of the raster at a specified lat/lon point.

I have:

  • postgresql-9.1
  • postgis-2.0-svn with raster support
  • a raster imported into PostGIS its SRID is 3035
11

You can transform the lat/lon point to raster CRS on the fly using ST_Transform(). Combined, the query looks like this:

ST_Value(your_raster, ST_Transform(ST_SetSRID(ST_MakePoint(lon,lat),4326),3035))
5

The function ST_value:

http://postgis.net/docs/RT_ST_Value.html

returns a raster value given a point in either x,y or lat,lon.

  • it works, but in this page the examples forces you to input your query in EPSG:3035, and i want to query in lat lon points.. – avances123 Sep 24 '11 at 15:49
4

While ST_Value works, you still need to spatially join to the point as well:

SELECT ST_Value(your_raster.rast, ST_Transform(ST_SetSRID(ST_MakePoint(lon,lat),4326),3035))
FROM your_raster
WHERE ST_Intersects(your_raster.rast, ST_SetSRID(ST_MakePoint(lon,lat),4326),3035))

Or with a table:

SELECT ST_Value(your_raster.rast, ST_Transform(ST_SetSRID(ST_MakePoint(your_table.lon,your_table.lat),4326),3035))
FROM your_raster
JOIN your_table ON ST_Intersects(your_raster.rast, ST_SetSRID(ST_MakePoint(your_table.lon,your_table.lat),4326),3035))

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