[OSM-talk] contours on main map

[Steve Hill]

On Thu, 8 May 2008, Robin Paulson wrote:

> alternatively, are there any world wide maps out there with contours
> and osm data, that update regularly?

The cycle map and the piste map both have contours for selected areas.
I'm generally doing monthly updates to the piste map data.  As far as I 
know, no one is serving contours for the whole planet - there are a couple 
of reasons:

1. The SRTM3 dataset for the whole planet is pretty huge once it has been 
processed into contour lines and put into PostGIS (probably about half a 
terabyte).
2. It isn't as simple as just rendering the same contour lines everywhere 
- for example, the piste map uses much wider spaced contour lines than the 
cycle map because the terrain is (generally) more mountainous.  To make a 
global contour map you would need to make the renderer vary the number of 
contour lines used depending on how mountainous the terrain is.

Also, whilst having the ability to turn on contour lines would be useful, 
I certainly wouldn't recommend having them on by default since the tiles 
are usually quite large compared to the average contourless tile (so a 
bigger bandwidth bill, more disk space needed for the tile cache, slower 
navigation around the map, etc).

  - Steve
    xmpp:steve at nexusuk.org   sip:steve at nexusuk.org   http://www.nexusuk.org/

      Servatis a periculum, servatis a maleficum - Whisper, Evanescence