[OSM-talk] road classes
Richard Fairhurst
richard at systemeD.net
Fri May 26 15:54:48 BST 2006
Lars wrote:
> Are Collins Bartholomew maps in these scales in general considered
> useful and accurate? Or do they often make unexpected omissions?
I only know about the UK maps at this scale, I'm afraid, but:
There are certainly some mistakes: it's just taken me 60 seconds
scrolling around the UK to find two. (A road south of Lichfield is
mistakenly classed as A38, and the declassified B4544 in Aston
Clinton, Bucks, is still labelled as such.)
The positional accuracy can be way out, far, far beyond what
generalisation might demand. I used the same Bartholomew dataset for
the mapping at Waterscape.com, which has (OS-derived) canal lines
superimposed, and it's sometimes embarrassing how much the
superimposed lines don't tally with the canal lines on the Bartholomew
rasters. (To be fair, this level of positional accuracy is not
remotely a concern for the target users of such a map.)
But omissions? I'm struggling to find any. On average, I'd say the
Bartholomew maps at that scale make a better job of selecting which
roads to include, and which not, than the Google Maps at a comparable
scale.
cheers
Richard
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