[OSM-talk] Proposal for import guidelines

THEVENON Julien julien_thevenon at yahoo.fr
Wed Sep 26 12:07:30 BST 2012


>>>> De : Lester Caine <lester at lsces.co.uk>

>>>> That has been a previous request :) The google translation is a little strange.
OK I was not aware about that



>>>> And if we can automate that process it would help you?
The add of source tag is already automatic


>>>> I'm just repeating things that were being quoted earlier, but I would 
like to have a look at the data myself to see if we are talking about 
the same things. Accessing the French data is difficult for a non French speaker :(
Ok. So by exemple to see official data goto on www.cadastre.gouv.fr
In "Commune" field type Saint Galmier
In "Departement" liste choose "42 - LOIRE"
Then click on "rechercher" button

In "Ville commune" list choose "Saint Galmier 42330"  ( I know this is painfull.... )
Click on "Rechercher" ( bottom right )
Click on "Vue d ensemble de la commune".
Normally you should have a pop up window that display cadastre data. You can zoom/unzoom on it using left panel to make details like river, building, streets appear.
This is for the official data.

The corresponding processed data that you can find on http://cadastre.openstreetmap.fr/data/ are those data downloaded in PDF format processed by a C++ script that analyse geometrical forms and colours to extract buildings, railways, rivers and produced separated OSM files.
You have one directory per french department ( in the case of Saint Galmier this is number 42 named LOIRE ) containing all the OSM files of cities belonging to this department. In my example case the data corresponding to what you have seen on cadastre.gouv.fr are located in these files:
http://cadastre.openstreetmap.fr/data/042/I1222-SAINT-GALMIER-city-limit.osm
http://cadastre.openstreetmap.fr/data/042/I1222-SAINT-GALMIER-rails.osm
http://cadastre.openstreetmap.fr/data/042/I1222-SAINT-GALMIER-water.osm
http://cadastre.openstreetmap.fr/data/042/I1222-SAINT-GALMIER.tar.bz2

The french wiki cadastre page provide a big warning aout poor quality of water data and the fact that we need to perform some verifications and cleanup of all these data ( building, railways, river etc ) has the analyse is not perfect.


>>>> I can't access the government data as an overlay? The English 
translation is a little light, but I suspect this only give hard copy 
output? IS the raw data available in a manor that we can access directly in a josm or something similar?

You can have cadastre has overlay in JOSM using french cadastre plugin.
If you want to perform the test on Saint Galmier you will have to install the plugin in JOSM, restart JOSM. Change the projection to "Lambert 9 zones" and choose Lambert CC zone "5", restart JOSM.

In cadastre preferences ( just behind plugin part of preferences dialog window ) choose vector Grab Multplier "100m" thanks to the radio button.
Then in JOSM "Cadastre" Menu choose "Cadastre grab"
In the dialog box type "SAINT-GLAMIER" in Commune field. In department list choose "42 - loire". Click on OK and normally you should slowly have a new overlay representing french cadastre data. Notice that their are coming in picture format.

I'm not sure about if this is possible to do the same with Merkaartor


>>>> The cadastre.openstreetmap.fr seems to a similar problem? I can select a Department and then in some cases Ville, but nothing seems to happen?
Please refer to explainations at the beginning of my email and let me know if you are still facing issues


>>>> There is obviously good data available, and all I'm asking is some help 
in viewing it. In the same manor as data is being made usable elsewhere 
;)
>>>> The UK's OS data is available as 'layers' we can work with, and it 
would be nice to see the French data similarly available.
>>>> We have to 
process the raw OS data into a raw format that is correctly 
geo-referenced, and that raw data is available, so I would anticipate 
that the French data has had similar processing?
>>>> Is that raw data 
available anywhere? Having got the raw layer(s) we NOW need to process 
them into a 'staging' layer which can be used to integrate later updates - all of which should be made available as raw layers - but the staging layer would be the one that flags what has or has not been merged. 

>>>> So 
I'm not sure if cadastre.openstreetmap.fr is your 'raw data' layer, in 
which case there should be a 'version select' or your staging layer?

The georeferencing is already there for vectorised data of cadastre ( for raster cadastre data this is much more complex than the example I provide to you and we hae no automatic tools at all to 'integrate' them).
We have currently no historic versionning.
For the other points I`m not sure to understand what you mean so I hope that the explaination on how to access to official cadastre data and processed data will make things more clear....

Cheers
Julien
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