[Talk-GB] Council Footpath data

[Robert Whittaker (OSM lists)]

On 24 May 2018 at 14:33, Nick Whitelegg <nick.whitelegg at solent.ac.uk> wrote:
> Following on from the recent topic regarding 1900 historical footpath data,
> I'd like to clarify exactly what we can and can't do currently with the
> council RoWs if possible.
>
> a) Copy designation status from council data to OSM?
>
> b) Trace an entire RoW from the council data onto OSM?

Using any data is ok legally if and only if it's available under a
suitable licence. Whether it's desirable to use it depends on its
accuracy and completeness. For rights of way, there are generally
three types of data/information available from councils that we might
want to use:

* The Definitive Map -- usually lines showing the Rights of Way drawn
on top of an Ordnance Survey (OS) base map.
* The Definitive Statement -- a narrative description of each Right of Way
* Electronic GIS data containing the routes of each Right of Way.

The Definitive Map and Statement form the legal record of Rights of
Way. They're "Definitive" in that if a route is included there it is
legally Right of Way, even if there's a mistake. So apart from
discrepancies between the two documents, they don't contain errors by
definition. (Though they can be incomplete, i.e. there could be Rights
of Way that aren't recorded in them.) The GIS data (that most councils
have created) is based on digitising the routes from the Definitive
Map. This dataset is usually not the legal record, and could contain
transcription errors or be out of date.

In terms of permitted usage in OSM, the Definitive Maps are off-limits
because OS claims copyright over derived maps. However, OS doesn't
claim any rights in the Definitive Statement, and OS does allow
councils to release the GIS data (without the underlying base maps)
even though it was derived from OS mapping originally. Therefore, if a
council can be persuaded to supply and suitably licence the Definitive
Statement and GIS data, then it can be used in OSM. The licence needs
to be compatible with the ODbL. The standard Open Government Licence
v3 (OGL3) meets this requirement, but be wary of councils still
releasing stuff under the now-obsolete OS OpenData Licence that was
not compatible with the ODbL. I have a (very incomplete table of which
councils have released what under appropriate licences at
http://robert.mathmos.net/osm/prow/progress/open-data -- any help to
update this would be appreciated.)

In terms desirable usage in OSM, I would generally assume that the GIS
data is an accurate representation of the Definitive Map, particularly
if it is consistent with the Definitive Statement. Therefore you could
in principle use it to armchair map Rights of Way from scratch.
However, I'd say this generally isn't a good idea, as you'd not be
able to include any of the physical characteristics of the route, and
wouldn't know if/how it crossed any field boundaries, ditches, streams
etc. Just because a route is a Right of Way, doesn't mean it's
physically usable on the ground. On the other hand, if a route is
already mapped as a highway of some sort (or can be so mapped from
licenced aerial imagery), and aligns with a route in the GIS data or
as described in the Definitive Statement, I would encourage people to
add appropriate designation=*, prow_ref=*, and access tags. If the
route on the ground differs from the Definitive Line, then I'd
recommend mapping both as separate ways: one as the physical
path/track that exists for people to use, and one as the legal line of
the right of way. My thoughts on appropriate tagging can be found at
https://wiki.openstreetmap.org/wiki/User:Rjw62/PRoW_Table

In case anyone hasn't seen it, I've got a tool for comparing councils'
GIS data to OSM mapping at
http://robert.mathmos.net/osm/prow/progress/ . The matching is based
on tagging OSM ways with designation=* and prow_ref=* (so it doesn't
explicitly look for non-tagged highways that might line up with RoWs
in the council data) and it doesn't check the matched routes line up
apart from a check on the overall length and bounding box of each RoW.
There are only 8 authorities listed there at the moment. At the time
those were the only ones that I knoew of that had released their GIS
data under the OGL. I know a few more have since, but I haven't got
round to adding them. If anyone would like any new authorities added
that have released their data under the OGL, then please get in touch.

Robert.

-- 
Robert Whittaker