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Use of Rights of Way Data in OpenStreetMap

Introduction

With the exception of Inner London Boroughs and the Isles of Scilly, all UK county councils, metropolitan borough councils, and unitary authorities are required by law to maintain a "Definitive Map" and a "Definitive Statement" describing the Public Rights of Way in their area. More recently, several councils have seen the benefit of producing an electronic or online map of their Public Rights of Way. This involves digitising their paper-based maps in order to produce an electronic data-set containing details of the routes and taken and the status of each one.

These official documents and data-sets can potentially be very useful to OSM mappers to help them verify and complete Rights of Way mapping. Details of requesting copies of, and the right to re-use, these documents can be found on my Advice for Requesting Rights of Way Documents from UK Councils page. This pages addresses the questions of what information can be used in OSM, and how it might be most appropriately used.

Documents / Data Available

Using any data is legally permitted if and only if it is available under a suitable licence. Whether it is 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 and Statement form the legal record of Rights of Way. They are "Definitive" in that if a route is included there it is legally Right of Way, even if there is a mistake. So apart from discrepancies between the two documents, they do not contain errors by definition. (Though they can be incomplete, i.e. there could be Rights of Way that are not 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 This dataset is usually not the legal record, and could contain transcription errors or be out of date.

Legally Permitted Use

In terms of legally permitted usage in OSM, the Definitive Maps are off-limits because OS claims copyright over derived maps. However, OS does not 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 https://osm.mathmos.net/osm/prow/open-data/.

Desirable Use

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 would say this generally is not a good idea, as you would not be able to include any of the physical characteristics of the route, and would not know if/how it crossed any field boundaries, ditches, streams etc. Just because a route is a Right of Way, does not mean it is 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 licensed 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 would 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