Just finished my first town

Posted by pieleric on 13 February 2011 in English (English)

I've just finished mapping my first town in OpenStreetMap, and coincidently it's also the first town where I lived: Crépy-en-Valois. Completed it using mainly the "cadastre" from the French authorities, and the Bing imagery, and the memories I have from spending 15 years there (turned out to be extremely useful).

Of course a place is never fully mapped, but here is can be found:
* all the streets
* all the streets names
* the shape of every building

I finished by naming the streets, and to ensure the quality, I compared the list of street names found on internet (from the phone directory) to the list in OpenStreetMap. I converted the directory data into a text file with one name per street alphabetically sorted.

To get the list of streets in OSM, the nominatim service seemed the most appropriate but I seemed not to answer this type of query. So eventually I settled with a very basic command:

curl -g ",49.2131958007812,2.93606853485107,49.2601203918457"

| grep =\"name | sort -u | sed -re "s/.*v=\"(.*)\".*/\1/;s/'/'/" > names-osm.txt

As long as there aren't many amenities, it works fine. Then using a diff tool (I used Meld), you can see which street is still missing, or where there are spelling mistakes. It turned out to be really useful. In addition to knowing there are 212 streets in such a small town, it even allowed me to notice small streets I had forgotten to map, and some streets whose name are not on the cadastre!

Location: Chemin des Docks, Crépy-en-Valois, Senlis, Oise, Nord-Pas-de-Calais and Picardy, Metropolitan France, 60800, France

Comment from Strash on 13 February 2011 at 14:42

I don't know (and I don't think so) if it's legal on OSM licence to use the Phone Directory (which isn't distributed with a free licence) even if it's just to compare to find missing streets.
Be very careful, you Must only use free data source in order be in accordance with OSM licence.

On the other side, good job for your work. I also did my home town as my first town in OSM (Castres, Tarn), and it was a really good experience. You learn a lot about the town you thought knowing by heart.

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Comment from chillly on 13 February 2011 at 16:04

Using the telephone directory data is not good. We need to be very careful about our sources of data. If you want to know the street names, why not walk / cycle around and write them down or photograph the signs? That way you will also find all of the extra things that are missing from the imports and anything that has changed since the data was last created. OSM may have Street in its title but it is about so much more than just roads.

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Comment from pieleric on 13 February 2011 at 20:04

Just to be clearer, I didn't copy the phone directory data into the map, I used principally the names which are in the cadastre (that the French authorities confirmed it was ok to use as a source for OSM). I'm using directory data only to get a second list, made independently, to follow the progress and ensure the quality. Actually the phone data I found is very low quality. It contains many spelling mistakes, missing words (like first name of people), and wrong street types (like "Street" instead of "Avenue"), so it would be impossible to use it directly.

When doing the comparison, whenever there is a discrepancy I try to validate the name by looking for it in the municipal newspaper, or asking some locals (eg: my parents).

I absolutely agree that doing it gives you a strong will for an actual tour around the place. I've already planned to go for a bike trip next time I visit my parents to see all these various places which I don't know enough to draw them yet!

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Comment from Roman Fischer on 14 February 2011 at 12:09

Good work! I really like to see more towns/villages with buildings because I think it looks so much more "alive". :)


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Comment from Rovastar on 14 February 2011 at 21:16

Good job, ignore the paranoid here about using other sources. As long as you don't copy directly is it ok AFAIC.

Comparing stuff offline I can never see a problem as if you find anomalies and check by hand. Ask people, walk street, other legal sources, etc

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