[OSM-talk] Contour lines

Steve Hill steve at nexusuk.org
Tue Apr 13 09:59:47 BST 2010

On Tue, 13 Apr 2010, Gregory wrote:

> What makes you think the Yahoo! imagery and/or the contour lines shown on
> the Cycle Map(these  contours are from SRTM data, not OSM) are more up to
> date or more accurate/precise than the existing water body drawn in OSM?

Indeed.  Also, ISTR the cycle map fakes up realistic looking contours for 
void-filling doesn't it?

I don't think the SRTM contours are accurate enough to use for tracing 
bodies of water - you need to walk the perimeter with a GPS or use aeriel 
photos.  SRTM data _may_ be useful for guestimating flowing water courses 
that can't be otherwise surveyed, but for this I think you'd really want 
to be computing stuff off the raw DEM rather than manually adding 
features using the (already quite heavilly processed) contour lines.


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

      Servatis a periculum, servatis a maleficum - Whisper, Evanescence

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