[Talk-GB] UK Quarterly Projects

Andy Townsend ajt1047 at gmail.com
Mon Mar 14 21:09:36 UTC 2016


On 14/03/2016 20:50, Rob Nickerson wrote:
> My concern with rivers is that we don't have tools to measure progress 
> - taginfo gives a count of nodes/ways/relations whereas we'd want 
> total length of features per region (in miles/km).

I'd agree that tracking progress with that one would be tricky. I've 
mapped lots of rivers and streams from a combination of survey, imagery 
and OS OpenData, and while we've got something approaching the "length" 
of major rivers and streams, what we've got in some areas is largely 
ex-NPE, and in many cases some distance from the actual waterway on the 
ground.

GPS traces (unless there are lots) and Bing imagery can of course be 
misplaced, but OS OpenData is normally pretty good (actually better than 
the OS vector data that people have imported in a couple of areas) 
although it can be wrong when watercourses have changed, and the top end 
of small Welsh streams is often a bit "wishful thinking" in OSSV - where 
in reality there's just a boggy mess the OS sometimes has well-defined 
streams.

The other problem with the waterways we've got in OSM is that many are 
just either "stream" or "river" - with things that I'd normally map as 
drains and ditches just in as "stream".  Obviously changing a tag 
post-survey is pretty straightforward, but it's something else to bear 
in mind.

There is a real benefit of having OSSV streams, ditches and drains in 
though - it's often clear that a watercourse hasn't moved for years, and 
it can then be used to help align imagery and GPS traces.

Cheers,

Andy (SomeoneElse)





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