2018-04-23 15:05 GMT+02:00 Rahkonen Jukka (MML) <
[email protected]>:
> Hi,
>
>
>
> That structure is most usable for constructing overviews from different
> data sources, not by subsampling higher resolution data. Nice trick for
> making one virtual topomap with different rendering rules for different
> scales.
>
>
>
> I can see that there is something that supports GDAL virtual rasters in
> https://github.com/geosolutions-it/imageio-ext/tree/master/plugin/gdal/
> gdalvrt. On the other hand, it is possible to collect overviews from
> different sources by using GDAL VRT format http://www.gdal.org/gdal_
> vrttut.html#gdal_vrttut_overviews and http://osgeo-org.1560.x6.
> nabble.com/gdal-dev-Scale-dependent-VRT-for-overviews-td4966814.html.
>
>
>
> So perhaps GeoServer can support the structure that you have but
> developers just don’t know it yet.
>
>
>
We do this because it speeds up generating overviews quite a bit (taking an
overview to generate an overview instead of sampling the whole tiff - this
used to be an issue with gdal, not sure if it still is), and makes
mapserver a little less resource hungry, because the .ovr files get smaller
each round (each next one is about 25% of the previous).
gdaladdo -ro <some other options> some.tiff 2
gdaladdo -ro <some other options> some.tiff.ovr 2
gdaladdo -ro <some other options> some.tiff.ovr.ovr 2
gdaladdo -ro <some other options> some.tiff.ovr.ovr.ovr 2
gdaladdo -ro <some other options> some.tiff.ovr.ovr.ovr 2 4 8 16 32 64
Building on gdal mapserver picks this up fine, but this particular case
requires geoserver.
I'll just kick off a new gdaladdo for now.
Thanks, Mark
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