[OSM-dev] Coastline generalization tool and data

[Michal Migurski]

On Feb 19, 2013, at 4:04 AM, Christoph Hormann wrote:

> On Tuesday 19 February 2013, Michal Migurski wrote:
> 
>> 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.

It's mostly 4, actually. The individual road segments are being simplified and merged.


> 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.

No rendering at all. The intent of this work is to provide labeling hints, so you'd still render the regular roads from OSM and use this dataset to place labels over them. We did this for the US when I worked on the Stamen Terrain map, visible here:
	http://maps.stamen.com/terrain/#13/37.7786/-122.4408


>> 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


So a re-tag would fix this? How long does the data take to re-run?

-mike.

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