[Talk-GB] Ordnance Survey

Andy Robinson (blackadder-lists) ajrlists at googlemail.com
Mon Apr 5 20:31:59 BST 2010

Jason Cunningham wrote:
>Sent: 05 April 2010 7:53 PM
>To: talk-gb at openstreetmap.org
>Subject: Re: [Talk-GB] Ordnance Survey
>On 5 April 2010 14:10, John Robert Peterson <jrp.crs at gmail.com> wrote:
>	Put differently -- can anyone think of any specific reason why we
>	can't start tracing?
>	Thanks,
>	JR
>JR, you might spend hours tracing Streetview images only to find someone
>replaces it with 'VectorMap District' vector data in a couple of weeks. Why
>trace the road when the vector data behind streetview will be released next

Different products and covering the ground in different ways. Don't assume
what you see on StreetView is in 'VectorMap District because the trial data
they have released suggests not.

>I've had my first look through the various datasets this afternoon and I'm
>really pleased. I agree with those who say we need to wait before tracing,
>because we'll probably be using 'VectorMap District" which is released next

VMD may be useful for targeted importing but Streetview is probably going to
be better for general stuff. For instance, VMD doesn't appear to have minor
streets named, eg residential streets.

>Each of the products released by OS contains data which may be of use to
>OSM. We now need to look at the data within each product, decide what we
>want to use, and how the data enters OSM.
>The dominant source of data looks like being the data 'VectorMap District'
>product, because its vector data and accurate. But there will be data in
>Streetview not available in VectorMap District which will need tracing.

Define accurate. I'd expect the position of most roads and major features to
be at least as good as we have now but is it up to date. Just because it's
the OS doesn't automatically mean its better than what we have in OSM

>At this moment I do not support a straight import of any data from
>'VectorMap District' because much of the data is already present in OSM.
>I'd suggest something along the lines of converting the 'VectorMap
>Discrict' data for each 2km grid square and making it available as a
>download that can be used as a layer in JOSM. The corresponding area in OSM
>can be downloaded into JOSM and the two 'brought together' if needed. Which
>I guess may mean deleting a lot of existing OSM data because OS have mapped
>more accurately in many situations.

Its going to need a lot of care this, It could be a great aid to someone who
is mapping on the ground. It would save editing time. But if its done
remotely we may be no better off than the situation with Yahoo! imagery. If
VMD doesn't have naming attributes on all objects, and the trial data
suggests it doesn't, then it may not be of as much use as we think. 

>I've had a look at the vector data provided for Milton Keynes and it's
>clear we will need to discuss the individual layers available. Hopefully on
>the wiki?
>For example the 'water area' contains far more detail than I ever hoped to
>see, and its a very important layer for many "map users". It inclusion
>really stands out when you consider the missing fence lines and 'Rights of
>OS appear map the 'areas' of waterways over 1m wide, something OSM has not
>been able to do with GPSr's and Yahoo imagery. (Waterways under 1m are
>shown as lines by OS)

Yes, I can see that water features is one area the OS vector data could be a
big improvement for OSM currently.

>Looking at the waterways layer (and woodland layer) provides examples of
>why we couldn't directly import it. Whenever there is a bridge over the
>waterway the water way stops existing. Similarly the existence of a path
>causes woodland not to exist over the path, so instead of one large
>woodland, it's broken up into several small woodlands. (Maybe this is one
>of the issues OS will address before the release of 'VectorMap District'
>next month?)

Don't hold your breath!

>For example I used the example vector data for Milton Keynes to look at the
>water layer. Below the first link show you can see example of the very
>accurate vector data within 'VectorMap District'.
>Its a stream running through Milton Keynes and less than two metres wide.
>But the layer is broken up because the stream is not considered to exist
>under bridges! The bridges/paths can be seen in the second link to "Where's
>the path"

One very good example of using OS data as a reference resource and not
wholly relying upon it for direct import.



>Jason Cunningham
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