Hi Christian, Thanks for your reply. OK, so I don't need my custom zoom levels.
But I have one question remaining : two of the zoom levels that will be requested are smaller than the resolution of the original data (0.166667 and 0.333333 are smaller than the original 0.5). So I would need to increase (instead of decrease) the number of pixels to create the lowest pyramid level. Or is it useless considering the way geoserver handles pyramid data ? Alain ----- Mail original ----- De: "christian mueller" <christian.muel...@nvoe.at> À: "Alain Camus" <a...@ngi.be> Cc: gdal-dev@lists.osgeo.org Envoyé: Lundi 22 Août 2011 14:04:03 Objet: Re: [gdal-dev] How would I build a custom pyramid ? Zitat von Alain Camus <a...@ngi.be>: > > Hello list, > > I have a set of tiles at resolution 0.5 m/pxl. Based on this data, > I'd like to create a pyramid that has zoom levels 0.166667, > 0.333333, 0.666667 and 1.66667 (the data will only be viewed in > geoserver at these levels, so I guess it will be faster if I prepare > the data at these levels). Geoserver will rescale your raster data depending on the envelope in world coordinates and the pixel dimensions. It es very unlikely that a request needs one of your precalculated resolutions. Pyramids lower the amount of calculations giving you a better response time. Within geoserver, pyramids are hidden. you see only one layer, the logic chooses the best fitting pyramid level and does the required calculations. I would try a gdal_retile job with 10 pyramids and look at the result in geoserver. A zoom level of 2 means that 4 pixels are reduced to 1 pixel. The 10th pyramid reduces a 1024x1024 pixel area to one pixel. Cheers Christian > > I think gdal_retile only allows multiplying the zoom levels by 2. > Thus I think I will need those steps : > > > 1. gdal_translate to get the lowest zoom level (0.5 --> 0.166667) > 2. gdal_retile to give these tiles the good size in pixels, > mosaic them and to create the next two levels (0.333333 and 0.666667 ) > 3. gdal_translate again to get the highest zoom level (1.66667 , > which is not the double of the previous one) starting from the > 0.666667 tiles . > 4. gdal_retile again to give these tiles the good size in pixels > and mosaic them > 5. manually adapt the pyramid config files > > At 0.5 m/pxl, I have 8000 geotiffs each 4000 x 4000 pxls, so I think > it'll take a lot of time, especially steps 1 and 2. > > Would you have an advice to speed up the process or decrease the > number of steps ? > > Alain > > > > > ---------------------------------------------------------------- This message was sent using IMP, the Internet Messaging Program. _______________________________________________ gdal-dev mailing list gdal-dev@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/gdal-dev