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

Figure 3.3: Physical storage of GeoRaster data [3].
value and data values for each band) with its georeference (pixel type, upper left pixel center, rotation
and spatial reference system identifier (SRID)).
A single raster attribute may be composed of many bands having a common size, pixel size and
georeference. The storage used for raster bands is band sequential (BSQ) in which each band has its
pixel type and its nodata value.
One table with a column of type raster is called raster coverage. One table row with a column of
type raster is called tile. Thus there are no differences between rasters and tiles. A tile is a raster and
a raster is a tile in which each tile has all that are necessary to do basic raster operations.
Figure 3.4: Physical storage of PostGIS Raster data.
Another important advantage of PostGIS Raster over Oracle GeoRaster is the georeferencing
approach [14]. As Oracle GeoRaster uses a one-georeference-by-layer georeference schema instead of
one-georeference-by-raster one, so non-continuous raster data cannot be stored in the same raster data
table. That means that Oracle GeoRaster requires one raster data table for each raster file loaded
when these raster files are from irregular raster coverage. In contrast, PostGIS Raster allows only one
table for all kinds of raster coverages, regular or not.
In addition to this traditional storing method (storing in-database raster), PostGIS Raster enables
user to simply register basic metadata (path to the actual file, pixeltype, with, height, georeference)
of images stored in the file system, without having to load their data values into the database. This is
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