[MapProxy] Generate complete cache from one scale
Rahkonen Jukka (MML)
jukka.rahkonen at maanmittauslaitos.fi
Tue Aug 25 23:49:55 PDT 2015
I work with aerial images also and I have been thinking about this as well. I am already doing principally the same thing on the WMS side when I generate the overviews for the images with gdaladdo.
I have been thinking sometimes that modifying gdaladdo to save external overviews into MBTiles/rasterlite/GeoPackage format might work but the I thought that the tiled source layer should be combined together somehow with a huge GDAL VRT which does not feel optimal. However, it might be worth having a look on how gdaladdo works because simply merging and resampling tiles in a groups of four could give artifacts at the boundaries of the new tiles. And at least average resampling would be necessary for getting better quality overviews.
Perhaps there could even be a top-quality mode for resampling from higher level tiles. If the native resolution is Z-15 it would be used for the first overviews Z-14 and Z-13, and Z-12 would be resampled from Z-14 and so on. Add some advanced resampling methods and a possibility to use filters like sharpen or unsharp mask in the resampling chain and it could well be possible to get better looking overviews from MapProxy than what the original source WMS is delivering.
Oliver Tonnhofer wrote:
> On 21.08.2015, at 11:38, dirk.thalheim at bkg.bund.de wrote:
> I have a source which provides raster data (aerial images) only for a single scale. Is it possible to configure mapproxy in that way, that a complete cache could be generated from that source?
> In theory it would be enough to cache the source scale and after that recursively generate all lower scale caches by resizing the previous cache. My first approach would be to configure a recursive cache configuration. But this seems to me like a huge configuration and I’m not pretty sure how to combine the single caches in a single one for production. Or is there a simpler way?
No, there is no easy way to handle this right now. But it would be a great feature for MapProxy. It would also help for services that only provide maps for higher scale, but not for low scales (overview).
Oliver Tonnhofer | Omniscale GmbH & Co KG | http://omniscale.com
OpenStreetMap WMS and tile services | http://maps.omniscale.com
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