[OSM-dev] Holes in contours

[Steve Hill]

On Tue, 16 Sep 2008, Gregory wrote:

> I noticed the Cycle map has a small hole on that link, here it is zoomed
> in:

Small holes in the SRTM data are common - they are usually caused by the 
radar being obscured by a mountain, since the radar data wasn't collected 
from directly above.  The SRT missions took radar readings from the Space 
Shuttle's orbit, so it gets progressively more holey at higher latitudes 
as the angle of the radar beam becomes less perpendicular to the ground.

The problem I am trying to solve is that the piste map seems to have much 
larger areas in Canada where there is no data, which do not match up with 
similar areas on the cycle map.  Since both the piste map and the cycle 
map are using the same SRTM3 data set, this shouldn't happen, and 
presumably is caused by a difference in the toolchain used.  As far as I 
know, both the piste map and cycle map are using the same toolchain, so I 
guess the problem will be down to a version specific bug in one of the 
tools.

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

      Servatis a periculum, servatis a maleficum - Whisper, Evanescence