On 09/03/11 11:57, Michael Collinson wrote:
At 12:32 10/02/2011, Andy Robinson (blackadder-lists) wrote:
Henry Gomersall [mailto:[email protected]] 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.
A further word of caution: Bing and all other imagery only shows a
snapshot of the way things are, often many years ago, and in an
indeterminate state of water level. Some rivers have tidal influences,
some rivers have very different levels in flood or drought. Sometimes
where the rough "verge" meets pasture land is the highest point the
water reaches regularly, but still only occasionally.
--
Cheers, Chris
user: chillly
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