PostGIS Raster : Extending PostgreSQL for The Support of ... - CoDE

sdo_geor.importFrom(geor, ’blocksize=(256,256)’, ’TIFF’, ’file’, ’srtm_new.tif’);
UPDATE spain_images SET image = geor WHERE image_id = 1;
END;
The same operation is repeated for every image file. If these images form a non-continuous coverage,
two new tables are needed for each image file.
Loading Using PostGIS Raster
When loading raster data by using GDAL driver, the loader creates all that are necessary to store
the raster data into a SQL file. It consists of creating the needed tables, the indexes (if it is specified)
and inserting raster data into the tables. A single or a set of raster images can be loaded all only once.
Example:
python raster2pgsql.py -r path\*.tif -t srtm_tiled -s 4326 -k 50x50 -I -M
-o srtm.sql
Next step is to execute the srtm.sql file using psql:
psql -d postgis_db -f srtm.sql -U user -W
3.2.6 Intersecting Raster and Vector Layers
Intersecting in Oracle GeoRaster
It is impossible to intersect directly raster and vector data in Oracle GeoRaster. Instead, what user
can do is to select a sampling window to clip an area of the raster and get raster data over this area.
The sampling windows must be rectangular or the round windows cannot be used (As described in
SDO_GEOR.generateStatistics documentation 2 ). So the MBR is used as solution.
In the following example, the sampling windows are the geometry objects stored in sampling_win table.
The request will calculate the intersection between the sampling windows and the spatial extent of
the GeoRaster objects [15]:
DECLARE
cellCoordinate mdsys.sdo_geometry;
ret varchar2(256);
gr sdo_georaster;
BEGIN
-- Intersect spatial extent of the rasters with the sampling windows
(SELECT t.id, t.geom, r.image_id as rid
FROM spain_images r, sampling_win t
WHERE sdo_geom.sdo_intersection(r.image.spatialExtent, t.geom, 0.005) is not null)
END;
Intersecting in PostGIS Raster
PostGIS Raster uses st_intersection() and st_intersects() functions, that operate directly
on raster and vector data, to calculate the intersection. Before doing the intersection, the
st_intersects() will check which portion of raster is intesected by vector. So the st_intersection()
intersects vector with raster by vectorizing only the necessary part of the raster [8]:
CREATE TABLE vector_srtm_inter AS
SELECT id, (gv).geom AS the_geom, (gv).val
FROM ( SELECT id, ST_Intersection(rast, the_geom) AS gv
FROM srtm_tiled, vector_data
WHERE ST_Intersects(rast, the_geom)
) inter;
2 http://docs.oracle.com/cd/B28359_01/appdev.111/b28398/geor_ref.htm#CHEDCICI.
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