[OSM-talk] Combining OSM waterbody and elevation data for better map rendering and QA
Christoph Hormann
chris_hormann at gmx.de
Thu Sep 12 12:59:31 UTC 2013
Hello,
I have completed a first version of a tool to modify elevation data by
use of waterbody data from OSM (more precisely currently only the
lakes, not the rivers). Description of the process is on [1], the tool
on [2].
Primary purpose is better display of lakes in 3d renderings but this can
also be useful for relief rendering in 2d maps, i.e. avoiding contours
intersecting lakes and for more accurate elevation profiles of routes.
The problem is of course that the processing takes some time (Europe at
1 arc second resolution about a night) and changes in the waterbody
data would require updates.
As a byproduct the process also puts out lists of possible errors in the
waterbody data - places where the modification of the elevation model
required is so large it cannot be correct. From my first look these
have a fairly good signal to noise ratio, i.e. the majority of them are
actually errors in the OSM data (a large fraction are shadows in
imagery that have been incorrectly interpreted as water like at [3] and
[4]). I put up a simple map to look at these for Europe on [5] but you
can also find the point list on github. In the long term this is not
overly useful as a QA tool without frequent updates of course.
Greetings,
Christoph
[1] http://www.imagico.de/map/dem_water_en.php
[2] https://github.com/imagico/dem_water
[3]
http://tools.geofabrik.de/mc/?lon=23.91222&lat=39.24613&zoom=13&num=2&mt0=mapnik&mt1=bing-satellite
[4]
http://tools.geofabrik.de/mc/?lon=6.02164&lat=60.45423&zoom=13&num=2&mt0=mapnik&mt1=bing-satellite
[5] http://www.imagico.de/map/errormap_en.php
--
Christoph Hormann
http://www.imagico.de/
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