[Talk-us] Tagging Ridges as ways

stevea steveaOSM at softworkers.com
Fri Jul 26 20:52:05 UTC 2013


I have tagged numerous ridges (dozens, at least), always as a way. 
To me, it doesn't make sense for a ridge to be a single node, that 
semantic might be better conveyed with natural=peak.  I include a 
medium-sized mountain range, the Santa Cruz Mountains 
(www.osm.org/browse/way/174808173), almost 120 kilometers long, but 
which I seem to have captured with only 22 nodes.  True, I used 
natural=mountain_range (rather than natural=ridge) on this.  Neither 
natural=ridge nor natural=mountain_range renders in mapnik/Standard 
as anything besides text in the name=* tag.  And that seems about 
right.

The proposed feature natural=massif (a group of mountains) has been 
abandoned as inactive.

Just like any way (a road, a bike path...), use "as many points as it 
takes to accurately convey the line of the way, but don't use too 
many."  Of course, these values are subjective, but there is a 
certain middle ground to the calculus of curve-fitting.  OSM (via its 
human contributors) usually does a good job of finding this middle on 
most ways, but there are exceptions in both directions (i.e. too many 
points, as well as too few).

There are mapping tools (e.g. part of QGIS Desktop) which can help 
you de-node/simplify over-noded ways.  However, often the best way to 
do these is manually with an extra imagery layer that lets you edit 
the way while seeing a relatively sharp contrast of where the 
ridgeline is.  My example of a node every five or six km might be a 
bit sparse, but it works.  Find your happy medium:  often, starting 
with the highest peaks as a skeleton and connecting them with a way 
is a good way to "find the line," then you just keep adding nodes as 
you see fit until it is "accurate enough" for your taste.  There are 
such things as (national) map accuracy standards, but OSM doesn't 
claim to adhere to them.

SteveA
California


><http://wiki.openstreetmap.org/wiki/Tag:natural%3Dridge>http://wiki.openstreetmap.org/wiki/Tag:natural%3Dridge
>
>seems to suggest that the appropriate way to tag a ridge is as a 
>way. Any thoughts on this? I'm looking at 100+ ridges, wondering how 
>to simplify (de-node) yet keep the way roughly following to contours 
>of the feature it's supposed to be labeling.
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