[Talk-GB] National Cycle Network discrepancies between Sustrans and OSM data

[Ian Dent]

I’ve been on a campaign to get the accuracy of the Sustrans National 
Cycle Network improved for quite a while now and have made some progress 
in engaging with Sustrans.

I’ve found that the NCN plotted on OpenStreetMap differs in a number of 
places from that in the Sustrans mapping.

I’ve created a coarse visualisation of the differences – see 
https://dent.org.uk/sustrans/sustrans-ncn-inconsistences/ - which, by 
focusing on the thick red and blue areas shows which areas to 
investigate in detail. Note this is a snapshot at Feb 23 and won’t 
reflect any changes in OSM or Sustrans data until I update it. Also note 
it is intended to show where to focus and some of the smaller focus 
areas may be errors in how I’ve done the mapping.

I know the Derbyshire NCN fairly well and have found that most of the 
discrepancies are due to errors in the Sustrans data rather than OSM and 
suspect this may be the case across the country.

Sustrans have gone through a process of removing some of their routes 
and “reclassifying” others (i.e. not being responsible for them in the 
future). I’ve excluded these removed and reclassified sections from the 
map and the comparison with the OSM even though a lot of the routes 
still appear in OSM as they still have signage on the ground. I’m taking 
advice on what to do about removed and reclassified routes and will post 
a separate note on this subject later.

I’m keen that Sustrans internally review the discrepancies and make 
changes to their mapping when it is in error. I’ve had some success in 
discussions but it is a slow process! There is discussion about 
involving the Sustrans volunteer force who are very geographically 
spread and will have local knowledge.

I’m also keen to understand how best to communicate the discrepancy 
areas to people within the OSM community with local knowledge and who 
can, where the OSM is in error, make the necessary OSM changes.

Discrepancies are for various reasons including:

  *

    mismatches on how the route is mapped (the map shows differences of
    10 metres or more).

  *

    Routes that Sustrans have classed as regional but OSM as national
    (or vice versa). e.g. NCN 30 south of Lowestoft, NCN 568 on The Wirral

  *

    New Sustrans routes that haven’t yet reached OSM – e.g. NCN 28 east
    of Plymouth

  *

    Routes that Sustrans classes as “links” but OSM has as NCN – e.g.
    NCN 28 near Dartmouth. I think these are generally Sustrans errors.

  *

    Routes that OSM have included as NCN but which are not part of the
    Sustrans network. e.g. NCN 627 north of Sheffield, NCN 422 near
    Wokingham

  *

    Some ferries are included as routes in OSM – e.g. NCN 2 near Plymouth

Sustrans data for the NCN can be found at 
https://data-sustrans-uk.opendata.arcgis.com/ (Open Government Licence). 
Note that a lot of this isn’t accurate so don’t take it as gospel – on 
the ground survey is needed.

I’ll continue to work with Sustrans to try and get their errors 
improved. I’d appreciate advice on how to get the OSM community to 
consider the discrepancies and fix any OSM errors found (local knowledge 
needed).

Thanks to those who’ve already discussed this with me – particularly the 
recent East Midlands OSM meeting.

Ian
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