[Talk-GB] How to work with Government Open Data (e.g. Boundaries, Rights of Way)

[rob.j.nickerson at gmail.com]

Hi Nick,

I agree that we don't want to take Hants data at face value and load this  
into OSM where a path is already mapped. I have added my answers below:

Q1. Hampshire marked footpath and OSM footpath run very close to each other  
(deviating by only a few meters max). No obvious marking on Bing Aerial
Q2. As with Q1, but Bing Aerial shows clear path (neither OSM or Hampshire  
line up with this path perfectly).

A1. Use OSM path and tag with designation
A2. As A1 (optionally align path to Bing, GPS survey would help here).

- - -
Q3. OSM path crosses diagonally over a field (roughly following the path  
visible on Bing). Hampshire's data indicates a kink in the route so that in  
the middle of the field the gap reaches about 20-30 meters.
Q4. OSM path crosses over 2 fields (following Bing path and cutting through  
a gap in hedgerow). Path is a straight line at an angle 'x' from the road.  
Hampshire's data shows the path runs straight, but at angle 'y'. Max  
deviation 50m. What about a smaller deviation of only 15m?
Q5. As 4 above but the Hampshire path appears to cross the hedgerow where  
there is no visible gap on Bings imagery.

A3-5. Research using other sources (ground survey, NLS scanned OS maps,  
etc). If no path found where Hants suggests there should be one, tag the  
OSM path instead (add a note). If there is a path where Hants puts it, then  
this should be mapped -> This could result in 2 paths being mapped, but  
would be correct if there are 2 paths on the ground.

- - -
Q6. Hampshire have a path marked that is not in OSM. Bing shows there is  
something there.
Q7. As 6 but no marking on Bing. No obvious obstructions
Q8. As 7 but there is an potential obstruction (eg woodland with no clear  
path - although this would be hard to see on Bing)
Q9. As 8 but there is an obvious obstruction (eg building).

A6-9. Trace the path from bing for Q6 (add a fixme tag). Q7-9 really could  
do with a ground survey.

- - -
To test these rules I had a go at mapping BOAT "Martin. 15". Neither OSM or  
Hants data lined up well with the Bing aerial (even with a simple offset).  
In this example there is a clear modern track. Two sections of the modern  
track appear to deviate from the historic route (I looked on the NLS maps  
to get a better idea of the historic route and cross referenced this with  
Bing aerial). The right hand section is still clearly visible on Bing,  
suggesting it is still used. The left hand section follows what looks to be  
a tree lined route. This suggests that I have identified the  
correct 'historic' route, but the trees make it hard to tell if the route  
is still passable.

I mapped the whole of the 'modern' track as highway=track. The 2 other  
sections, I mapped as highway=path and added a fixme comment to suggest  
resurvey. I then added the designation=byway_open_to_all_traffic tag to the  
route that follows the 'historic' path. I was reasonable happy doing this  
because if the left hand section route is impassable there is a clear  
alternative. Let me know your thoughts on this.

Visualisation of edit history:  
http://osmhv.openstreetmap.de/changeset.jsp?id=11915562#lon=-1.93345046;lat=50.9691551;zoom=15;layer=Mpnk

- - -
Do you think it is worth adding a wiki page (eg "Missing Rights of  
Way/Hampshire CC") where we can keep track of any 'big' issues with the  
intention to pass this data back to Hants? This could include a list of  
Ways in OSM that we feel may be a Missing RoW and a list of OSM ways that  
deviate substantially from the route Hants have in their database.

Kind Regards,
RobJN

ps I'm not going to do many of the RoWs in Hampshire as I can't get down  
there to survey them. However, I am keen that we get a good 'best practice'  
in place so that we can use this to help persuade other councils to release  
their data (eg Work with us to improve your data), and to prevent differing  
approaches across the country.




On , Nick Whitelegg <Nick.Whitelegg at solent.ac.uk> wrote:

> What I wouldn't personally like is a mess where the Hampshire ROW line  
> *and* the line on the ground are *both* in OSM. This would make the data  
> messy and confusing to work with.

> In cases like this maybe the ROW has, to all intents and purposes,  
> shifted and the Hampshire data is out-of-date.

> Personally I would prefer that the Hants ROW data is *only* used to add  
> *new, unmapped paths* to OSM and not to adjust existing paths - unless  
> the existing path was mapped with some degree of uncertainty.

> Nick

> -----Rob Nickerson wrote: -----To: talk-gb at openstreetmap.org
> From: Rob Nickerson
> Date: 15/06/2012 06:18PM
> Subject: Re: [Talk-GB] How to work with Government Open Data (eg  
> Boundaries, Rights of Way)


> Yeah, I think it might me a slow process but if there is a clear problem  
> then may still be worth writing in to start the ball rolling.

> By keeping RoW and paths separate what do you mean? Add a way with a  
> designation=public_footpath (for example) without the highway tag?


> RobJN

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