[postgis-users] PostGIS WKT Raster

Pierre Racine Pierre.Racine at sbf.ulaval.ca
Mon Jul 14 12:43:20 PDT 2008

Paul Ramsey hasn't yet said my design was:

-a "meme" (http://blog.cleverelephant.ca/2008/06/x-my-l.html), 
-a "waste of time" (http://postgis.refractions.net/pipermail/postgis-devel/2007-July/002653.html) 
-"useless" (http://postgis.refractions.net/pipermail/postgis-users/2007-May/015578.html)
-that it was "pointless" (http://postgis.refractions.net/pipermail/postgis-users/2007-October/017250.html) 
-or that I was a "fool" (http://postgis.refractions.net/pipermail/postgis-users/2007-October/017239.html)

So I conclude it's a good design!!! :-) 

He asked for a good design some time ago for raster in the database (http://postgis.refractions.net/pipermail/postgis-users/2006-October/013628.html)

Where is the clever elephant?


>-----Message d'origine-----
>De : postgis-users-bounces at postgis.refractions.net 
>[mailto:postgis-users-bounces at postgis.refractions.net] De la 
>part de Pierre Racine
>Envoyé : 7 juillet 2008 11:30
>À : postgis-users at postgis.refractions.net
>Cc : warmerdam at pobox.com; nicolas.gignac at msp.gouv.qc.ca; 
>smarshall at wsi.com
>Objet : [postgis-users] PostGIS WKT Raster
>Hi raster people,
>I'm starting a 2-3 year project to develop a web-based application to
>automate certain GIS tasks commonly needed in ecological research. The
>tool will support queries over VERY large extent based on a Canada-wide
>assemblages of raster and vector data layers. The queries will 
>involve intersecting those layers with buffers defined around points or
>We would like to implement this system with PostGIS, but it currently
>does not to support raster data. We could convert all our data to a
>single format (raster or vector) and use other tools, however PostGIS
>seems to us the best and most powerful vector analysis tool available
>and we would prefer to use it. We would like to develop a unified
>toolkit so that the application mostly need not worry about 
>whether base
>layers are in vector or raster format. We are then strong proponents of
>having raster functionality in PostGIS. I have reviewed every thread on
>this list on the subject. I have analysed them and I have compiled them
>in the wiki
>The argument goes like this: The geodatabase paradigm has been a major
>recent enhancement in GIS technology, I feel that the seamless
>integration of raster and vector analysis should be one of the next.
>Spatial analysis is emerging, beside the making and publishing of maps,
>as one of the main desktop and web-GIS applications. Rastor/vector
>seamless integration is already done for display (in most GIS and with
>MapServer or ArcIMS on the web) but definitely not for 
>analysis. Desktop
>analysts must still learn to use two distinct toolsets within most
>(all?) GIS packages: one toolset for raster and another for 
>vector data.
>Would not it be easier to build and use applications if we had a unique
>data query and analysis toolset independent of the data model? I don't
>know any tool having this approach right now. A PostGIS foundation that
>addressed this problem would offer better directions to application
>developers than the dichotomic one proposed by ESRI since their
>beginning. It would provide the necessary abstraction to develop GIS
>with ONE set of analysis tools. I feel this is one good reason to
>integrate raster in PostGIS. There is "GIS" in the word "PostGIS".
>PostGIS should then provide a COMPLETE GIS data foundation (read
>"base"!) for geoapplication developers. I think Steve Marshall's design
>is a good step in this direction
>At the same time, we would have a chance to reconsider the raster model
>as a coverage instead of a series of images. Spatial databases got rid
>of map sheets by allowing complete vector coverages to be stored as
>single table (e.g. the entire United States) This approach should works
>for raster data as well. Isn't this the approach taken by ArcSDE?
>In summary, I think we must stop thinking about PostGIS as a 
>mere vector
>data repository to support mapping applications. This is the way most
>objectors to raster integration seem to view it. We must think about
>PostGIS as a powerfull indexed data analysis tool. Seamless
>raster/vector analysis in the database could lead to a major
>simplification of geoapplications.
>I prepared a PowerPoint presentation with a complete specification of
>raster in PostGIS and an analysis of what should be the result of
>overlay operation between raster and vector layers. You can download
>this PPT at: http://www.cef-cfr.ca/uploads/Membres/WKTRasterPostGIS.ppt
>Please have a look at it, feel free to answer questions I ask and
>Here are the main propositions of this design:
>-Like a vector feature, rasters are stored as a subtype of "geometry"(a
>new WKB/WKT geometry type called RASTER instead of POINT or POLYGON)
>-There is no distinction between a raster and a tile. A tile 
>is a raster
>and a table of rasters can be seen as a tile coverage. Hence, contrary
>to Oracle GeoRaster, only one table is needed to store a coverage and
>there is only one type.
>-It support raster in the database AND raster out of the database. This
>mailing list has shown that both approaches have their pros and cons.
>Let's not impose one approach over the other.
>-It supports: multi-band, pyramids and variable nodata value, raster
>size, pixel size and pixel type for each row.
>-It supports import/export from/to Tiff and JPEG.
>But moreover seamless raster/vector integration is materialized by
>theses propositions:
>-A lot of existing vector-only functions are adapted to work 
>with raster
>-Most new raster functions are also implemented to work with vector.
>Only basic raster derivation functions are proposed.
>-Most vector/vector existing functions are adapted to work seamlessly
>with raster/vector or raster/raster
>I also want to ask:
>-What is the status of PGRaster? Is any development now underway?
>We have some resources to devote to this project over the next 
>few years
>and are very interested in forming collaborations to move this work
>Pierre Racine
>GIS/Programmer Analyst
>University Laval
>postgis-users mailing list
>postgis-users at postgis.refractions.net

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