[Talk-GB] Adding missing roads using Facebook detections

[SK53]

Dear All,

Coming late to this as I have little time for any email at present.

I would suggest in the current circumstances that this activity should be
halted:


   1.  As others have said the vast majority of public roads in Great
   Britain (and most likely Northern Ireland too) are already mapped.
   2.  The latest release of OS OpenData Roads has good quality geometries
   and it is relatively simple to find missing roads with it (see below).
   3.  Missing roads available from the Facebook project via the special ID
   editors have such a high rate of false positives (I haven't found the time
   to precisely quantify it but I would estimate 90-95% for the Rushcliffe
   District in Nottinghamshire). This in itself ought to be sufficient reason
   to halt/delay on its own.
   4.  Imagery used for the identifications may well be less up-to-date
   than OS OpenData
   5.  Classification of roads often requires good local knowledge. The
   ability to improve a very small number of areas in comparison is not
   outweighed by the potential to introduce many incorrect routes across rural
   areas which, in particular, may impact some logistics planning.
   6.  Active OSM contributors have much less time to check any data added
   and flag up issues. Accordingly incorrect data may stay on OSM for a
   considerable period of time.

In order to identify and add missing urban roads I suggest one or more of
the following:


   -  Use CodePoint Open to identify postcodes more than a certain distance
   from the OSM road network. Probably needs OSM road network (e.g., for a
   Local Authority or larger area) and CPO either in a PostGIS database or as
   layers in QGIS. The relevant query is st_shortestline(cpo_point, osm_road)
   > n metres. It needs optimisation to get good performance, but is probably
   fine for a single LA.
   - Download a OpenRoads. I think it comes packaged as 100 km sq tiles
   (e.g., SK). This is a reasonable volume of data to work with in QGIS. It
   can be clipped to a given LA, although you may need two or more squares for
   some. Download OSM highways (minus tracks, bridleways, steps, footways &
   cycleways, or filter them out after download), either using Overpass (best)
   or a full pbf file from Geofabrik. Re-project to OSGB 27700, buffer by
   anywhere between 10 and 20 metres and then use the Vector difference tool
   in QGIS to find all roads in the OpenRoad dataset which are not overlaid by
   the buffered OSM data (this latter step is not absolutely necessary because
   overlaying the buffered OSM roads allows a quick visualisation of the
   missing data. OpenRoads data can be read by JOSM directly using the
   OpenData plugin which will perform a correct reprojection for OSM purposes.
   Roads to be added can be selected and added to a new layer. The default
   fields, other than name and ref, from OpenRoads are largely not useful for
   OSM, nor do they map cleanly onto OSM tags, so tags need to be added,
   original fields deleted etc., before data is added to OSM. (The OpenRoads
   data is also very good for missing road names).

Regards,

Jerry

On Fri, 27 Mar 2020 at 12:18, Richard Fairhurst <richard at systemed.net>
wrote:

> Jothirnadh Guthula wrote:
> > With a team of mappers @Amazon we are planning to improve
> > missing roads in UK using Facebook detections as a source. Please
> > let us know if you have any ongoing projects using this data source.
> > While adding missing roads, we will be adding all the associated
> > access tags as per available on-ground resources.
>
> I'd urge extreme caution on this, particularly in rural areas, for two
> reasons.
>
> Firstly, as Martin says, there are virtually no public roads unmapped in
> the
> UK. New construction aside, I think in the last five years, I've spotted
> two, both in Powys.
>
> Secondly, UK access rights are unique and complex, and can only be
> discerned
> either by survey or by consulting Definitive Statements where these exist.
> You should not be adding access tags, nor adding highway types that imply
> access rights (for example, highway=unclassified implies general public
> access to all vehicle types), unless you've surveyed the location or
> consulted a Definitive Statement.
>
> For an example of the issues, please see this changeset discussion:
>
>     https://www.openstreetmap.org/changeset/71668172
>
> In this case an Amazon Logistics mapper added motor_vehicle=yes which was
> inaccurate. In this particular case I was lucky to find an openly licensed
> photo to demonstrate the real access rights on that way.
>
> If you're exclusively mapping new housing estates in urban areas, though,
> go
> for it. :)
>
> Richard
>
>
>
> --
> Sent from: http://gis.19327.n8.nabble.com/Great-Britain-f5372682.html
>
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