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

[Lester Caine]

Jean-Marc Liotier wrote:
>> Jean-Marc Liotier wrote:
>>> Without the isolated clusters of buildings, how would you know that some
>>> important
>>> roads are missing ?
>> Visiting the village and walking around it?
> Are we now reaching the crux of this discussion ? Do you believe that local
> survey is a requirement for mapping ? I don't and I back my position with all
> the places I have mapped without having visited them - I'm curious about what
> criticism you'll express about the quality of my work.
There is a certain level of accuracy that can be achieved as an armchair mapper 
and there is certainly a lot more detail that can be added world wide using just 
the material currently available. I was very tempted to 'tidy up' one of the 
French areas as an example and I may yet do that, but there is more than enough 
work still to do in my local area. AND only local access allows me to correct 
the mistakes in the 'official' data.

> If the opposition to mapping with the assistance of cadastral data is grounded
> in opposition to the principle of remote mapping, then we have a problem - and
> maybe you should talk to everyone who uses some provider of orbital imagery in
> the source tag.
I'd certainly appreciate it if the editors automatically added 
'source:trace=xxx' where I'm using a particular background layer - heck I forget 
to ADD the tag most of the time!
With regards data, one needs to know the limits of it's accuracy. I know that 
some streetview data is 40 years old. I can even identify the map it originally 
came from, so it has to be a judgement if I use it. The positional accuracy of 
the cadastral data is what I am questioning. Either someone says 'this is our 
reference' and we ignore the differences to other imagery, or it gets tidied up 
and the obvious flaws such as extra diagonal lines are removed. I get the 
impression that this is a process that should be happening but not everybody is 
'complying', so something needs to be done to re-educate those mappers to the 
'assistance' element over the 'just copy raw' activity?

-- 
Lester Caine - G8HFL
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