Just to mention that I did try the gdal driver for PGRaster and it is working. I can't tell the speed, and like mentionnend Simon it depends of many things. But I did succeed to render (query and write to disk as an ascii file with prj file) a 100x100 pixels 32b float, single band using gdal_translate in the latest release version.
Etienne On Mon, Jan 31, 2011 at 10:46 AM, Pierre Racine <[email protected] > wrote: > Sunny, > > > > There are two planned options for serving raster from PostGIS raster: > > > > The first (1) is to just register the raster as out-of db raster. Only the > georeferences of each tile/raster is stored in the database along with the > path to the raster itself in the filesystem (you can add any other attribute > as additional columns). PostGIS raster in this case act like a quick SQL > raster catalog. Actual raster data (pixel values) are not stored in the > database. They are store as JPEG or TIFF in the filesystem. It is up to the > application to fetch them where they are. In this case their should be no > performance lost comparing with any existing raster server solution storing > raster coverage in the filesystem. This options still need > testing/improvement. For example, the loader (raster2pgsql.py) is not able, > right now, to split big raster into multiple JPEG tiles when you use the –k > option. It does it only when you store the tiles in-db. > > > > The second (2) option is to store everything in the DB. The raster is then > stored in the PostGIS raster format and need to be converted to JPEG before > being sent to web client (desktop applications do not have to rely on this > conversion as can implement native support for the PostGIS raster WKB format > or rely on GDAL). There are two ways to convert PostGIS raster to JPEG or > whatever: the first one (2.1) is to rely on the PostGIS raster GDAL driver > used by the application (this is how we got almost free support in > MapServer). The second one (2.2) is to ask the database to convert PostGIS > rasters to JPEG or whatever format with SQL functions like ST_AsJPEG(rast) > or ST_AsTIFF(rast) so that the application receive a JPEG or TIFF binary > stream. These function are planned but not yet implemented. This option > should be a bit slower than the first as raster are converted on the fly. > > > > Option (1), storing out-of-db, targets applications needing VERY faster > retrieval not requering raster edit or analysis and not implemented to read > native PostGIS or GDAL raster. > > > > Option (2), in-db storage, targets applications needing raster edit or > analysis and able to read native PostGIS or GDAL raster. > > > > Options 1 and 2.2 assume that raster tiles can be sent to the web > application without having to be blended with other layers. Application > (like MapServer) that has to read and blend rasters with other layers before > sending them should rely on 2.1 (GDAL). I think this last option has the > better future. It is however not very well tested right now and the GDAL > driver just got reimplemented in december. We might have to tweak it at some > point to get the kind of performance expected by web applications. > > > > I suggest you give a try to MapServer (Regina & Leo explain how to > configure it in PostGIS in Action) and, if it is not fast enough, see with > Jorge what we can do. > > > > To answer your other questions: raster loading in PostGIS raster is quite > fast even if it still need improvement like not passing through a large > intermediate SQL file. > > > > Could you elaborate a bit more on the multiband issue? I’m not very > familiar with tile caching tech anymore. > > > > Pierre > > > > > > *From:* [email protected] [mailto: > [email protected]] *On Behalf Of *Sunny Teo > *Sent:* 29 janvier 2011 21:25 > *To:* PostGIS Users Discussion > *Subject:* Re: [postgis-users] PostGIS Raster Performance > > > > Hi Regina, > > > > Thanks for the lead on this. > > > > It opens up the light and the room for discussion. Well, as far as I know, > Oracle Georaster is not good for serving purpose and on top of it, that > takes awful amount of time to load the data into Oracle. I assume that its > not the case with PG Raster. > > > > The other issue is, even if one dont want to do store the multiband (say 8 > band) imagery into the PG Raster for the Speed issue, can we target to link > up the Cache into this? If GWC or Tile Cache jpg/png tiles can be kept here > and then publish... it will be nice. Again, the issue will be speed ... or > some may argue the fact the it defeats the purpose of Cache which is suppose > to be non "ram" required serving. > > > > my only wish, that one day we should be able to easily load the images into > PG Raster and publish into a web application and get a performance/speed as > good as any image servers. > > > > btw, it was a news to me that GeoServer dont support PG Raster yet... I > hope they are working on it now... > > > > > > Thank you; > > Sunny > > > > > > On Sun, Jan 30, 2011 at 6:30 AM, Paragon Corporation <[email protected]> wrote: > > Sunny, > > > > Good question. I suspect it will be worse at least at the moment (just as > PostGIS was worse when it first came out than reading from shapefile). How > much worse I'm not sure. If you try and see speed issues, we can tackle > them, but it hasn't really been our main focus. > > > > I suspect no one has tested it extensively as far as dishing out large > datasets. The primary focus of PostGIS Raster is for analysis and then > secondary is the rendering. That is not to say it will work badly or we > don't care about rendering speed, just that the GDAL drivers etc. needed by > Mapserver probably still have a few wrinkles which would make it suboptimal > for that kind of work. The more people use it and find issues, the faster > issues will be addressed since we would have data points to go by. > > > > As far as GeoServer goes, I recall reading a thread where Chris Holmes said > he would work on a PostGIS Raster support for GeoServer, but not sure where > that is down the pipe, but to my knowledge, GeoServer does not YET support > PostGIS raster. > > > > Hope that helps, > > Regina > > > ------------------------------ > > *From:* [email protected] [mailto: > [email protected]] *On Behalf Of *Sunny Teo > *Sent:* Saturday, January 29, 2011 3:44 AM > *To:* [email protected] > *Subject:* [postgis-users] PostGIS Raster Performance > > List, > > > > Can anyone comment on the "Performance" of the PostGIS Rater or WKTRaster ? > > > > If you were to serve this onto a web application, how effective are they? > Well, I'm talking of very large datasets like 10GB each and 100 of them. How > does it compare with serving the images as files directly.. from a GeoTIFF, > ECW, Sid, etc. (obviously using Geoserver/Mapserver or some specialized > image serving solution) > > > > Been searching all over the web for the answers, but no luck. > > > > Hope to get some insights from the users. > > > > > > > > Thank you; > > Sunny. > > > _______________________________________________ > 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 > >
_______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
