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

[James Derrick]

Hi Ian,

On 25/02/2023 20:45, Ian Dent wrote:
>
> 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.
>
Looks like an excellent piece of GIS comparison work, and as a regular 
cycle mapper in Northumberland, useful.


Q: Do you see this as an aid to local mappers for direct survey/ OSM 
edit / engagement with Sustrans, or are you looking to collect 
discrepancies for wider discussion please?


A quick look at the comparison across Northumberland suggests:

* Most of the flagged discrepancies are down to low-polygon mapping such 
as on corners or "wiggly routes". OSM looks more correct.
   e.g. Blyth South Beach dunes - although it's full of dog walkers, so 
use the Links Road path!

* There are some minor changes due to new features - e.g. Cambois has a 
new roundabout, which OSM includes but NCN1 doesn't.

* There are some differences where I've personally surveyed on two 
wheels, and the route doesn't match the signs (e.g. Blyth, Ridley Park).

* Minor oddities that look like armchair simplification without ground 
survey by a local ranger (e.g. North Seaton underpass - why cycle down a 
ramp, then up steps, when you just go around?).


That leaves a few areas for checks:

* Alwinton has a **very** different route - don't know which is better / 
more correct.

* Shields Ferry is odd - 72 diverges from 1 & 10. Think this bit is 
uphill then back down, so historic with a better direct route created 
later? (there is some NCN art here)

* Blyth King Street - The King Street road route disadvantages cyclists 
(busy junctions, crossings, no priority), so the cycleway along Maddison 
Street is better.

* Duridge Bar Country Park - the "pretty" route via the park has lots of 
walkers, so I cycle up the coast path. It's interesting that OSM has the 
"pretty" route.

* Amble centre - OSM bypasses the busy town centre, which is quicker and 
safer but has less pasties.

* Seahouses looks like an optional loop, with a mapped bypass.


Thanks and Happy Mapping,


James
-- 
James Derrick
     lists at jamesderrick.org, Cramlington, England
     I wouldn't be a volunteer if you paid me...
     https://www.openstreetmap.org/user/James%20Derrick