[OSM-talk] All you've ever wanted to know about the french cadastre

[Lester Caine]

Joakim Fors wrote:
>> Not having access to the cadastre layer I can't comment on the differences between what has been traced and the source data, but I can SEE a distinct positional difference between the bing layer and the OSM buildings. If there was a general offset, then I would accept that there was simply a referencing error, but the buildings were offset in different directions across the areas I looked at. I also have buildings that do not yet appear on Bing ... no problem with that, but the ones that appear on both SHOULD be in the same place? You have already said that the cadastre data can't be trusted for detail?
>> >
> A lot of times Bing imagery is distorted in different directions in a small area. Quite easy to see in some places where you have access to very precise ortho imagery or vector data to compare with. For example in Lund where we get ortho imagery from the municpality; Here the Bing layer is distorted in different directions just a few blocks apart… not to mention that the Bing imagery is quite a few years older. Same with some vector data that muncipalities in the region have provided to OSM where it is easy to see that Bing imagery is quite inaccurate.

Sorry but I do not see any problem with the bing imagery in the area I 
identified. I moved up to 'Prayssas' being the first identifiable location I 
found, and I find it very strange that someone has imported a lot of buildings 
without any reference to roads to access them. I could understand if these 
buildings were then used to add the missing roads, but I've found no problem 
with the location of imagery against other sources in the UK so you would have 
to provide some pretty good evidence that the imagery around 'Prayssas' is 
distorted! I am used to the way building heights affect the ground plan, but if 
anything, the buildings are offset OVER the missing roads. The church looks 
nice, but google streetview only seems to cover the outer ring road :(

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Lester Caine - G8HFL
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