[Talk-ca] GeoTiff in JOSM

Paul Norman penorman at mac.com
Fri Sep 9 06:07:45 BST 2011

xjjk has put up his scripts at

gdal2tiles-mp.py is the multi-threaded version
Rename-TMS-layout-to-Google-Layout.py	 creates a script that renames

For your 6 hour run, what resampling did you use, how big was the source
GeoTIFF (with or without overviews) and what was the highest zoom range

> From: Tyler Gunn [mailto:tyler at egunn.com]
> Subject: Re: [Talk-ca] GeoTiff in JOSM
> > I believe you can also have JOSM get files directly from your hard
> > drive, but I'm not sure the syntax  to do so on the Mac.
> I did a render with gdal2tiles and was able to get it working fine in
> Merkaator.  Something about the tile number origin being opposite in
> > Maptiler is essentially a graphical front-end to gdal2tiles. Xjjk's
> > version is the command line version modified. My iMac broke awhile
> > back so I'm not sure how easy/hard GDAL is to set up with python
> bindings on OS X.
> Ah, okay.  I'll have to drop Xjik a line and see if I can get a copy
> of the modified command line file.   It seems there WAS a version of
> gdal2tiles tat was optimized for multi-core, but the author seems to be
> charging for it.
> There is a pre-made gdal install package for OSX, so it was extremely
> easy to get up.  Click and install.
> > You'll still be limited by your CPU :P
> On a single core my 1.9GB image took around 6 hours.  So not too bad but
> faster would be nice.
> > What I did for testing was work on a small section downloaded
> > separately and benchmarked with different image scaling methods. The
> > three worth considering are nearest, antialias, and lanczos. Nearest
> > is fastest, preserves sharp edges but has the worst quality. Antialias
> > is decently fast, decent quality. Lanczos is the best quality,
> > preserves edges but is extremely slow.
> I'll have to try modifying the render settings and see how it goes.
> I'll probably want to get the parallelized version first though.
> THanks!
> Tyler

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