[Xastir] maps: how many are too many?

[Jason KG4WSV]

I've been playing around with some OSM tile mapping in other
applications (tangogps, etc).  I know xastir has some OSM tile
support, but it's meant for online operation.

So, I started playing around.  I'm using an ubuntu VM on my macbook
pro.  2.66GHz i7, 4Gb RAM, 1 processor allocated to VM.

The OSM tile coordinate system is fairly straightforward.  A little
hacking resulted in a script that will download maps for a given
rectangle and zoom level, so I can preload a map cache (for tangogps).
 Grab files for areas where I live, work, and play. Surprisingly, this
only results in about 1.8Gb of data.

Yet more hacking results in a script to generate .geo files for
everything in the tangogps/OSM map cache.

Now then, let's feed 'em to xastir.  In case you're curious, it takes
about 3 or 4 hours to index 250,000 new maps.

Operations that involve "managing" maps - changes in maps selected for
display, zooming, or just opening the map chooser with "expand dirs"
on - can be quite slow.  Like come back in 10 minutes slow.  Once you
get the map view you want, things are surprisingly back to normal.
panning around redraws in normal time, even though at the moment I
have 100,000+ tiles to chose from, plus a set of TIGER shapefiles to
render on top of that. zooming is fine, too, unless I zoom far enough
to change the mapset.

Conclusion: using xastir pre-rendered map tiles for detailed data for
a large area is not practical at this point.  If you change OSM zoom
levels, the penalty is just too high.


Next step, see if I can shoehorn a map rendering engine, web server,
and caching proxy server onto my xastir box and see if that is
feasible.

Or maybe I should just tweak/create some dbfawks so the shapefile
lines and labels are fat enough for me to see 'em while driving.

-Jason
kg4wsv