[Qgis-user] Qgis-user Digest, Vol 100, Issue 29

[Julian Schall]

Hi Jukka, Jonathan and Etienne,

the last days I had time to test a bit with what you recommended to me.
Thank you very much so far, your advices where very helpful and conductive
to deeper understanding in this topic.
What have I done:
First I tried to calculate what levels for the pyramids I need, but at the
end I still was not quite sure because the answers of you led to different
results. Anyway me feeling is that I need levels about 35 and higher.
In addition I didn't wanted to change the .jpgs into .tiffs for some
reasons.
First approach: gdaladdo -r NEAREST -ro --config JPEG_QUALITY_OVERVIEW 75
--config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR --config
INTERLEAVE_OVERVIEW PIXEL "U:\\xy.vrt" 35 40 45 50 55 60 64 
gave me an Error after days of computing.
Second test: gdaladdo -r NEAREST -ro --config JPEG_QUALITY_OVERVIEW 75
--config COMPRESS_OVERVIEW JPEG --config PHOTOMETRIC_OVERVIEW YCBCR --config
INTERLEAVE_OVERVIEW PIXEL "U:\\xy.vrt" 8 16 32 64
gave me an error after a night of computing.
Third test: gdaladdo -r NEAREST -ro "U:\\GIS\\Dienstleister\\Runkel\\Thema
Rasterdaten ins QGIS\\ortho2010_mitStatistik_neuer Pfad_JS.vrt" 32 64
was sucessfull. The .ovr is about 500MB big. That's moderate and I think in
comparison to the catalogue without pyramids my impression is that reduced
resolution is on scales about 1:25.000 and smaller.

Now I'm gonna try it again for levels 32 and 64 but this time with the
option high compression.

Regards,

Julian