[Talk-GB] Incorrect use of OS VectorMap District when mapping?

[Barnett, Phillip]

I don't think you can infer OS methodology from comparison of OS and Bing photographs of rivers. Rivers are not static objects - they move laterally over time, unless confined by concrete, in towns etc. In the countryside they will migrate backwards and forwards by possibly many hundreds of metres over a few decades. Compare parish boundaries with Bing imagery, you'll see inexplicable bulges in the line, where they diverge from rivers, and then rejoin downstream.





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-----Original Message-----
From: Michael Collinson [mailto:mike at ayeltd.biz]
Sent: 09 March 2011 11:57
To: 'Talk GB'
Subject: Re: [Talk-GB] Incorrect use of OS VectorMap District when mapping?

At 12:32 10/02/2011, Andy Robinson (blackadder-lists) wrote:
>Henry Gomersall [mailto:heng at cantab.net] wrote:
> >Sent: 10 February 2011 11:07 AM
> >To: Peter Miller
> >Cc: Talk GB
> >Subject: Re: [Talk-GB] Incorrect use of OS VectorMap District when mapping?
> >
> >On Thu, 2011-02-10 at 10:30 +0000, Peter Miller wrote:
> >> On reflection possibly we should use river-bank as that has more
> >> information in it, but recommend that anyone importing does a 'bridge
> >> cleanup' at the same time.
> >
> >This is an area I'm actually really interested in (for rural rivers) and
>keen to
> >contribute. So far I've been put off by exactly this problem. Is a
>reasonable
> >approach to use the OS data for river edges and then fill in the gaps
>(bridges
> >etc) with OSM data?
>
>+1
>
>If the OS vector data is only assumed to be the banks and the additional
>data for flow direction, bridges and other features are added from
>survey/BING etc then we should end up with a very functional dataset.

A late response to this thread, but a word of caution. Comparing Bing
imagery recently for several Yorkshire rivers with folk's riverbanks
derived from OS data indicates that very frequently  the OS are not
tracing the riverbank as the dividing line between water (clear river
channel) and land (grass, scrub) but the top of the riverbank or
where the rough "verge" meets pasture land.

Mike


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