Extract raster values at points

Question

How can I extract values from a raster by points. I prefer not in Arcgis. I prefer in Qgis or Mapwindow or other open source gis.

Answer 1

QGIS "Point Sampling Tool" should be the plugin you're looking for.

Here's a detailed description of how to use it: http://pvanb.wordpress.com/2010/02/15/sampling-raster-values-at-point-locations-in-qgis/

Answer 2

Hawthorne Beyer's GME tools do this nicely via command line, and allow easy batching with 'for' loops.

isectpntrst(in="path/to/shapefile", raster="path/to/raster", field="fieldname")

GME isectpntrst command reference

Answer 3

In GRASS GIS, you can either query the map in the GUI or use http://grass.osgeo.org/gdp/html_grass64/r.what.html

Answer 4

In PostGIS 2.0 you can do:

SELECT ST_Value(rast, geom) val
FROM yourrastertabe, yourpointtable
WHERE ST_Intersects(rast, geom)

Make sure your raster is tiled very small when you load it (-t 10x10 with the loader).

Answer 5

A quick thought, http://gis-techniques.blogspot.com/2012/10/extract-raster-values-from-points.html has step by step guide to use R Raster package extract raster values from points. Now days R raster package is popular for raster handling in terms of resource, easiness and quick and dirty job done.

Answer 6

If you have access to FME then you can use one of two transformers in FME Workbench.

The RasterCellCoercer ("Decomposes all input numeric raster features into individual points or polygons. One vector feature is output for each cell in the raster.")

The PointOnRasterValueExtractor ("Takes in point features and a single reference raster. The output consists of the band and palette value(s) at the location of each point.")

Answer 7

Quick thought:

1. gdal_polygonize.py - polygonize your raster feature
2. Insert your point features and polygons into PostGIS database
3. Use st_intersects function to pull all elevation values where features intersect