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? Pierre >-----Message d'origine----- >De : [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] De la >part de Pierre Racine >Envoyé : 7 juillet 2008 11:30 >À : [email protected] >Cc : [EMAIL PROTECTED]; [EMAIL PROTECTED]; >[EMAIL PROTECTED] >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 >typically >involve intersecting those layers with buffers defined around points or >transects. > >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 >(http://postgis.refractions.net/support/wiki/index.php?RasterNotes). > >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 >(http://postgis.refractions.net/pipermail/postgis-users/2006-De >cember/01 >4059.html). > >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 >comment. > >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 >also. >-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 >forward. > >Pierre Racine >GIS/Programmer Analyst >University Laval >http://www.cef-cfr.ca/index.php?n=Membres.PierreRacine >_______________________________________________ >postgis-users mailing list >[email protected] >http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
