Hi all,
I'm seeing some very strange performance from gdal2tiles on a
particular grid, so I'm wondering if someone has an insight into why
this is happening.
The problem is that when I tile the grid at zoom level 7, I get much
better performance than with other zoomlevels, including lower ones (!).
The grid is this (zipped PNG, ~2.7Mb):
http://dl.dropbox.com/u/53500018/ontarioOrigSizeTrimReprojected.zip
So, let's say I run this command:
gdal2tiles.bat -w google -s EPSG:4326 -z 1-7 -v
C:\temp\ontarioOrigSizeTrimReprojected.png
C:\temp\outputTiles
This takes about 16 seconds on my machine.
But if I replace the last line to be zoom level 1:
gdal2tiles.bat -w google -s EPSG:4326 -z 1-1 -v
C:\temp\ontarioOrigSizeTrimReprojected.png
C:\temp\outputTiles
This takes 32 seconds, or about double the time of tiling zoomlevels
1-7. Note also that I've experimented with other maximum zoomlevels
(5,6,8,9,10,11) and they all run slower than 7.
So, does anyone know Why does this strange behaviour happen on zoom
level 7? And is there any way to optimize the input to gdal2tiles for
better performance?
Regards,
Mladen
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