On Sep 27, 2012, at 2:18 AM, Paul Norman wrote:
>>> This is not an example that you only find after a long search; it is a
>>> typical cadastre import building.
>>
>> Until you can back up your claim with solid numbers, your claim, more
>> specifically the word"typical", is just FUD.
>> Furthermore it can hurt many hard working french contributors, who for a
>> single city spent dozens of hours integrating the cadaster into OSM.
>
> Time for some numbers then...
>
> Detailed data is available upon request.
Thanks Paul for taking the time to give some numbers. I don't understand also
the technical details but hopefully well enough to provide some feedback that
makes sense :)
Looking at your examples, I can see that some buildings have a geometry that
doesn't seem to be in line with the reality. However, like other persons
mentioned here already, the only way to find out if this is OK is to check with
a survey.
The problem is however real. I know that our french OSM gurus have some checks
for the cadaster import, but I don't know if it catches this kind of potential
errors.
Still, your analysis still doesn't quantify it well enough to entitle it
"typical". 1 day of data is really not enough to be representative. Also, it's
impossible to find automatically if adjacent building ways should be joined or
not ("wall" issue, adjacent but separate buildings…). I am not saying it's not
a problem, and I am not saying it's not typical, I am just saying there isn't
enough proof to say that yet.
> A significant number of cadastre imported buildings consist of multiple
> ways, such as in the example Frederik gave.
Could you summarize it in more simple wording and an exact number ?
For instance:
"10% of the new buildings imported between … and … share some ways with other
buildings that have the same tags."
Also, I didn't understand who you differentiate the cadaster imports from the
rest.
Cheers
Olivier
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