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

[Vincent de Chateau-Thierry]

Hi,

Le 27/09/2012 02:18, Paul Norman a écrit :

>
> Now, the analysis of geometry.
>
> One measure of how broken down into parts buildings are is to take the
> buildings, turn them into polygons, combine them into one multipolygon with
> ST_Union and then count the number of parts with ST_Dump and compare it with
> the original number of buildings. This does not consider buildings made from
> multipolygons (e.g. those with an inner hole). I get the following data
>
> Changeset  Joined  Original
> 13175035     3661      6341
> 13175649      503      1240
> 13176058      521       951
> 13176212      219       341
> 13176769      922      1510
> 13177032     1515      2782
> 13177569     2216      4291
> 13180264      536       830
> 13180628     1449      2230
> 13181698        2         2
> 13183198      506       883
> 13184921      286       462
> 13185567      255       438
> 13185645     1135      2373
> Total       13726     24674
>

I am not sure to understand the right way how you deal with multiple 
buildings sharing ways (= sharing walls IRL) and having each a different 
house number.
For instance how many "joined" buildings would give your analysis here :
http://www.openstreetmap.org/?mlat=48.86494&mlon=2.33&zoom=18&layers=M
= the block between Rue d'Alger and Rue du 29 juillet ?

vincent