[Talk-gb-westmidlands] [Talk-GB] Warwickshire footpaths - prow ref

[Robert Whittaker (OSM lists)]

On 7 July 2018 at 13:17, Rob Nickerson <rob.j.nickerson at gmail.com> wrote:
> I'm not sure if I will add the prow_ref as I'm not so sure it has much value
> given that they are not signed on the ground. I also don't know what code to
> add. Nick has it showing the Parish name/code, then a space, then the ref. I
> think this is just a copy from Barry's rowmaps datasets. In the Warwickshire
> data Barry has, it is a parish code (e.g. 214). This gives values such as
> "214 SS92/1".
>
> A quick check of the prow map that Warwickshire CC put online (scanned map),
> they only show the "SS92" part.
>
> In my WCC data (which I think is an earlier version that they released prior
> to Robert W forcing them to make it OGL), the parishes are listed by names.
> As an example, for one way I have these key=value pairs:
>
> ID_NO=SS92
> Type=BR
> DIST_BOR=Stratford-upon-Avon District
> Parish=Long Compton

Having looked at the Warwickshire IDs when I was adding them to my
tool, the initial letters correspond to former government districts,
and the paths are then numbered uniquely within each one. Parishes do
not feature in the numbering scheme, so I would regard the parish
information in the GIS data as being an attribute of the path (or a
section of the path) rather then being part of its ID. Accordingly I
would recommend that you use the prow_ref=SS92 format, without any
redundant parish information. (The prefix letters denoting the area --
SS corresponds to the former Shipstone-on-Stour Rural District for
example -- take the place of the parish name or code used in other
counties.)

A relatively small number of Rights of Way have letter suffixes (this
applies across other counties too). These correspond to separate
Rights of Way, and typically come about when an original Right of Way
is modified or diverted, and it's more convenient to retain an
association with the original number than to use a completely new one.
So please include an suffix letters in the prow_ref tag.

You'll also sometimes see /1, /2 etc suffixes added in GIS data.
Typically these are not part of the official PRoW numbering, but are
added by the GIS software to allow each PRoW to be split into
segments where-ever another PRoW connects to it. Since these aren't
part of the official numbering, I would not add them to the prow_ref
tag.

Counties seem to vary in whether they allow the same numbered route to
have multiple statuses. Some do not, in which case if part of a path
got upgraded or downgraded, then they'd need to assign a different
number (or suffix) to the different parts. Other Counties appear to.
But then I think it's ok in OSM to just have the same prow_ref=* value
with different designation=* values on different sections. (My tool
doesn't quite handle the latter situation correctly. The maps are
correct, but the table only lists one type for each number. I need to
alter the primary key in a database able to fix this -- which will
need some thought.)

As far as Warwickshire is concerned, my tool at
http://robert.mathmos.net/osm/prow/progress/warks/ looks for prow_ref
tags of the form '[area id][num][suffix]' using the regular expression
/^()([A-Z][A-Z]?)()([1-9][0-9]*)([A-Za-z]?)$/, so values like "SS92"
or "SS112b". Even if the reference number is not signed on the ground,
I think it's definitely worthwhile adding, as it then makes it much
easier for tools to check the completeness of Rights of Way mapping
and highlight any errors or discrepancies. See e.g.
http://robert.mathmos.net/osm/prow/progress/warks/stratford-on-avon/stratford-upon-avon-municipal-borough/

Robert.

-- 
Robert Whittaker