# Rasdaman GDAL driver

Rasdaman is a raster database middleware offering an SQL-style query language on multi-dimensional arrays of unlimited size, stored in a relational database. See www.rasdaman.org for the open-source code, documentation, etc. Currently rasdaman is under consideration for OSGeo incubation.

In our driver implementation, GDAL connects to rasdaman by defining a query template which is instantiated with the concrete subsetting box upon every access. This allows to deliver 2-D cutouts from n-D data sets (such as hyperspectral satellite time series, multi-variable climate simulation data, ocean model data, etc.). In particular, virtual imagery can be offered which is derived on demand from ground truth data. Some more technical details are given below.

The connect string syntax follows the WKT Raster pattern and goes like this:
rasdaman: query='select a[$x_lo:$x_hi,$y_lo:$y_hi] from MyImages as a' [tileXSize=1024] [tileYSize=1024] [host='localhost'] [port=7001] [database='RASBASE'] [user='rasguest'] [password='rasguest']

The rasdaman query language (rasql) string in this case only performs subsetting. Upon image access by GDAL, the $ parameters are substituted by the concrete bounding box computed from the input tile coordinates.

However, the query provided can include any kind of processing, as long as it returns something 2-D. For example, this determines the average of red and near-infrared pixels from the oldest image time series:
query='select ( a.red+a.nir ) /2 [$x_lo:$x_hi,$y_lo:$y_hi, 0 ] from SatStack as a'

Currently there is no support for reading or writing georeferencing information.

See Also:

- Rasdaman Project