[talk-au] Running stats against GPX files ...

John Smith delta_foxtrot at yahoo.com
Wed Jun 24 03:59:59 BST 2009


--- On Tue, 23/6/09, Sam Couter <sam at couter.id.au> wrote:
> It's true that XML is very verbose. However all that
> verbosity
> compresses extremely well, so it's not really a significant
> problem.

If you'd had said the cost of hdd space was approaching zero I'd have agreed with you.

When I was playing around with using gpsbabel to remove redundent points I found that compressing the output from my app and compressing the output from gpsbabel the gpsbabel file was bigger with only 1/3 the number of points.

Uncompressed the file with more points was double the size, but I still can't get over the fact that it was smaller when compressed.

Also with my previous answer, you can get away with only 14 bytes per point rather than 17, 3 bytes for time, 4 for lat, 4 for lon, 2 for time, 1 for hdop. Although if reset tracks that go over 65,000 seconds back to zero you could get away with only 13 bytes. No idea if this would compress well or not.

However 9000 points uncompressed with 13 bytes per point would give you about 115kBytes, the 9000 point gpx file I compressed came out at 35kBytes.

This link is to a trace with over 9000 points.

http://www.openstreetmap.org/user/Bigtincan%20Android%20App%20Account/traces/415786


      




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