[OSM-dev] Coastline generalization tool and data
Christoph Hormann
chris_hormann at gmx.de
Tue Feb 19 12:04:19 GMT 2013
On Tuesday 19 February 2013, Michal Migurski wrote:
> Christoph, this is so cool. Excellent work!
Thanks.
> I've been hammering away at an OSM generalization effort of my own,
> focused on the global preparation of simplified linework for major
> roads and route relations:
> http://www.openstreetmap.us/~migurski/streets-and-routes/
For generalizing roads I think there are four major components:
1. removing smaller roads where there is no room to show them properly
2. summarize dense networks of roads of similar size
3. move roads to be able to distinctly show them without overlap with
other features or themselves
4. simplify the individual road segments
From your description I have the impression that a major part of your
effort is in 2. although I could not clearly identify cases of
summarization in your examples.
From the samples it seems your technique sometimes produces gaps between
roads which are in fact connected. Apart from that it looks quite
good - for curved roads the simplification seems a bit strong unless
you mean to use some kind of smooth spline rendering.
By the way for the coastlines I also looked into the idea of using
vector skeletons but I soon realized this would be prohibitively slow
on a global scale. From the pure program design point this would still
be an interesting idea.
> I did find one weird part of your data, around Boston where the
> peninsula appears detached from the mainland.
That's another canal tagged as coastline:
http://www.openstreetmap.org/browse/way/22721484
--
Christoph Hormann
http://www.imagico.de/
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