[Talk-GB] Fwd: Footpath segmentation

Bill Chadwick bill.chadwick2 at gmail.com
Sun Dec 30 22:52:19 GMT 2012


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

http://www.rowmaps.com/kmls/

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&gt=1<http://wtp2.appspot.com/wheresthepath.htm?lat=51.71242566072326&lon=-1.3943651810922883&gz=15&oz=8&gt=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/ .
<http://download.geofabrik.de/openstreetmap/europe/great_britain/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

http://ukprow.appspot.com/map/prow_test.htm

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.

Bill Chadwick
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