[postgis-users] Rasters

[Randy George]

I am wondering about having imagery analysis functionality built into the
database? I think that a layer between the database and the viewer would be
where those functions would work best. For example GeoServer,
http://geoserver.sourceforge.net/html/index.php, can act as a WFS/WMS server
layer connected to PostGIS as one of its possible datastores. 

 

            I noticed some interesting alpha work going on over at the
GeoTools/GeoServer project. One of the capabilities in the works is adding
StreamingRenderer/GridCoverageRenderer which allows reprojection of imagery
as a WMS query.

 

            There is a screen shot here:
http://udig.refractions.net/confluence/display/UDIG/Screenshots in the
second row "Example of rendering from GeoServer reprojected in CRS
EPSG:42103 (WGS84 / LCC USA)" which shows an example of  reprojected WMS
query under a WFS query.

 

            This is a long way from the type of MapCalc operations you are
talking about but the same layered approach would be better than trying to
make PostGIS something more than it should be. The imagery could be stored
either in the file system or in a database - PostGIS . MapCalc functions
would be part of the server layer which could point to either type of
datastore . output view format selection could be part of the query allowing
multiple viewers to connect to the results either offline or online.

Views could be merged with WFS filter queries on top. So PostGIS tables with
geometry footprints and uri pointers to geotiff  imagery would work for
satellite Iconos imagery (1Gb) while some type of blob bytea[] fields could
be used for smaller images, like weather loop images (40Kb)
(http://www.web-maps.com/Hurricane/  ) Either approach could have Census
TIGER data shown over the top (way cool).

 

            I believe the OGC Grid Coverage Service specification
http://www.opengeospatial.org/specs/?page=specs is the place to look at how
analysis services could be set up in an open standard way. 

 

Randy

 

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