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

[Lester Caine]

Christian Quest wrote:
> So cross check with Bing
> must be done afterwards, exactly like when using vector data.
> That's why I consider manual tracing as a waste of time, and not high
> quality compared to using extracted building from vector data.

Christian
I've now seen your source data, and that is showing buildings as 'blocks'. In 
the PDF file are those blocks drawn individually when there are are more than 
one building side by side? Or are the vectors simply the outline of the whole block?

I'm sure that over time improved quality data will evolve, but the current 
vector data that many of us have access to is not ideal. Personally the problems 
I am finding is where we have semi detached houses drawn as a single block, and 
splitting that into two blocks is a pain on potlatch ... I've not tried on JOSM 
yet. But a tool on my 'wish list' is one I can use to select vector lines from a 
'staging layer' and combining them to a closed way to which I can then add extra 
tags. This I think is the best way to use this 'poor quality' vector data and 
convert it to better quality data? I can also see a 'split' tool, where the 
imported vectors are for a 'semi' or 'terrace' and you want to split each out to 
separate buildings.

http://www.openstreetmap.org/?lat=52.048913&lon=-1.85734&zoom=18 will show my 
own experience with all of this. What is not visible is the Opendata streetview 
layer, and just how bad the vector data is with respect to the current status. 
'New' buildings are actually not too bad, but none of the extensions on the 
houses on Smallbrook Road are present on the OS layer, which seems to be stuck 
with 40+ year old data. Some how I expect the same sort of discrepancies in most 
data, and so I would not use the OS data in the same manor you are using the 
French data, although with my historic hat on it WOULD be nice to retain the 
history of the additions of these extensions over time. Importing buildings from 
the Opendata streetview layer would fill up the UK map, but we do not know what 
date the buildings relate to and then updating and we still need to split and 
add address data ...

-- 
Lester Caine - G8HFL
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