On 5 April 2010 14:10, John Robert Peterson <jrp....@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 month? 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 month 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. 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. 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 Way'. 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) 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?) 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" http://i227.photobucket.com/albums/dd132/jamicu/grassvectorofwaterinMiltonKeynes.jpg http://snipurl.com/v9xsq Cheers, Jason Cunningham
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