[Live-demo] how much space for data?

Hamish hamish_b at yahoo.com
Wed Sep 2 07:09:27 EDT 2009


Using the OpenStreetMap -> PostGIS database + Mapnik + a tile generating
script from GpsDrive I have prepared local street maps for the SYD area
which I'd like to include on the disc to help folks figure out how to
get around town.

My question is- how much space on the disc would be appropriate for this?
Currently I have provided detailed 1:5000 maps for the CBD, main roads
out as far as the airport, and main highways overview from Wollongong to

If there is the space I'd like to include 1:10k local street maps from
Bondi to the Airport to Lewisham to North Sydney, but it starts to eat up
space rather quickly the further you go out.
So what's my disc space budget? 20mb? 50mb? 100mb?

A more space-efficient & cool display of tech, but potentially fragile
alternative is to store the OSM data directly in a local PostGIS DB and
allow it to render Mapnik maps on the fly, but I'd need someone's help in
cropping down the size of the PostGIS DB +world coastlines from
Australia- wide to just the Sydney area. The uncropped version would be ~
400mb, to make a wild guess, the Sydney area probably accounts for a
quarter of that data. So about the same disc space as I was looking at
for the .png tiles, but more detail+scale options.

I can shrink the PNGs more by converting them to JPEGs or some other
lossy method, but the tiny street names are hard enough to read when you
are bouncing along in a car already. Ah, compromises, compromises...

Current prefab tile settings:
 - bounding box is minlon,minlat,maxlon,maxlat
   (the tiles round outwards a bit from the coords given)
 - zoom level is the same as Google Maps/OSM Tiles/MicroSoft Maps all use

# 1:44k
gpsdrive_mapnik_gentiles --bbox "150.84,-34.0,151.3,-33.7" --scale 13

# 1:20k
gpsdrive_mapnik_gentiles --bbox "151.12,-33.95,151.26,-33.83" --scale 14

# 1:10k and 1:5k
gpsdrive_mapnik_gentiles --bbox "151.187,-33.89,151.226,-33.84" --scale 15-16


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