[Talk-GB] Fwd: Footpath segmentation
Nick.Whitelegg at solent.ac.uk
Mon Dec 31 09:00:50 GMT 2012
I was playing around with the same idea a couple of years ago and developed a utility to segmentise OSM data:
I think it worked reasonably well.
-----Bill Chadwick <bill.chadwick2 at gmail.com> wrote: -----
To: "Talk-GB at openstreetmap.org" <talk-gb at openstreetmap.org>
From: Bill Chadwick <bill.chadwick2 at gmail.com>
Date: 30/12/2012 10:53PM
Subject: [Talk-GB] Fwd: Footpath segmentation
Several UK local authorities have released their Public Right of Way data under a Open Data license
Barry Cornelius has been doing a great job of collating the data sets here
I have been processing these into UTF Grids at Google Zooms 13-15 to use for route creation aiding on my hike/bike/... route planning site here
http://wtp2.appspot.com/wheresthepath.h … &oz=8>=1
Press the Wand button (top left tool bar rightmost) then the Route button (bottom left tool bar, leftmost). You can then click e.g. along the Thames path building the route you want. Off PROW points, e.g. along a road, are included if no PROW is highlighted when you click. The PROW assistance can be toggled on / off at any time. On clicking a PROW it is linked to the existing route by its end nearest to the end of the route. When starting a route with a PROW, the end of the PROW nearest the click is used as the start. You can use use Right-Click to rub out route points from the end of the route. If you pick the wrong path.
Fortunately the released PROW data has a pretty good and consistent segmentation treatment with each path segment, between junctions with other paths and roads, being a separate feature.
As some of the honeypot counties like Cumbria have not (yet) released PROW data, I have been attempting to use OSM path data for those areas.
Unfortunately I find that the OSM path data has a wildly varying segmentation treatment. At Troutbeck, near to Windermere, you will find a very long path that goes all up Troutbeck, over Thornthwaite Crag, Froswick, Ill Bell and Yoke and then to the Garburn Pass.
This path is OSM is way 27577503 in cumbria.osm from http://download.geofabrik.de/openstreet … n/england/ . Such a long path is not very useful for off road routing as it has many junctions with other paths along its length.
I have had to implement a simple segmentation algorithm before using the OSM path data for route aiding. You should be able to see the segmentation as you mouseover the above path on my test page here
I would be interested to hear how council released prow data has / has not been used within OSM to add to or replace existing contributed path data. Hants and Devon have released PROW data but sadly many of the paths in the New Forest and Dartmoor are not PROW (black dashes on the OS 1:50K). It would be good to use a blend of OSM and council data in such areas but I am unsure how to avoid duplicate paths if there are paths in OSM not tagged as PROW.
Of course the best solution to all this would be for OS to release a national path data set as Open Data.
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