Again, geoserver will rescale to your zoom levels < 0.5 m/pxl. I would
take a small subset of your tiles (neighbors, of course) and make a test
Another important hint. What is your target platform ?. If your
platform supports native JAI as described here
http://docs.geoserver.org/latest/en/user/webadmin/server/JAI.html
you are lucky. AFIAK, this is the case for Windows/Linux.
Another idea. If you use gdal_merge to create on big geotiff picture
with inner tiling, you can use
http://www.gdal.org/gdaladdo.html to add your pyramids to the geotiff.
The prepared geotiff should work out of the box with geoserver.
Cheers
Zitat von Alain Camus <a...@ngi.be>:
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
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