[Talk-us] Over-digitized imports?

Alan Mintz Alan_Mintz+OSM at Earthlink.Net
Tue Aug 24 09:14:19 BST 2010


At 2010-08-19 20:24, Alan Mintz wrote:
>I'm mapping in this area: 
>http://www.openstreetmap.org/?lat=34.08242&lon=-118.639&zoom=17
>
>Along the north side of the tertiary road (whose name is not rendered, but 
>is Saddle Peak Road) is a state park polygon (Topanga State Park) imported 
>from CASIL. In this small segment, the road is approximated with less than 
>70 nodes, while the park polygon segment alongside uses over 1200. I've 
>noticed similar "beauty" in other data from this source and others (like 
>the Bakersfield data mentioned recently on the list).
>
>Should imports make an effort to "un-smooth" such data to some extent, for 
>the benefit of editing and rendering performance, storage, etc?

As a test case, I used JOSM's "Simplify Way" on the ways that make up 
Topanga State Park. After playing around a bit, in advanced preferences, I 
set simplify-way.max-error to 0.2, which still modeled curves to maybe 
single-digit meter errors, yet removed 73% of the nodes (from 9103 to 2466).

The ways are:
38458997
38459009
38459010
38459013
45753168
45753173
45753175

I'm not embarking on a mission to simplify all ways - just taking the 
(short time) to do this when I'm mapping an area anyway and see it could be 
of benefit.

--
Alan Mintz <Alan_Mintz+OSM at Earthlink.net>




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