[mkgmap-dev] [PATCH] POI Address Support, Country Region Autofill

Fri Feb 6 06:56:55 GMT 2009

Mark Burton schrieb:
> One thing though, the region names are wrong for a large proportion of the
> towns/villages/hamlets. Some are right, but a lot are wrong. How do you decide
> where the regions are?
>   

The algorithm works like this.

1. Step: Go through all cities an check if they have useful country 
region info

The best case is if the tags is_in:country and is_in:county are present 
thats easy.
Some cities have is_in information that can be used. I check for three 
different formats:

County, State, Country, Continent
County, State, Country
Continent, Country, State, County, ...

In "openGeoDb countries" this info is pretty reliable since it was 
imported from a external db into osm. Other countries have very sparse 
is_in info.

All this cities that have such info will end up in "city" list. All 
which lack such information in "location" list.

2. Step: Go through the "location" list and check if the is_in info has 
some relations to the cities we have info about.

Especially hamlets often have no full is_in information. They only have 
one entry in is_in that points to the city they belong to. I will check 
if I can find the name of this city in the "City" list. If there are 
more with the same name I use the closest one. If I can't find the exact 
name I use fuzzy name search. Thats a workaround for german umlaute 
since sometimes there are used in the tags and sometimes there are 
written as ue ae oe. I had a phonetic search in there but it was too fuzzy.

3. Step: Do the same like in step 2 once again. This is used to support 
at least one level of recursion in is_in relations.

If there is still no info found I use brute force and use the 
information from the next city. Has to be used for countries with poor 
is_in tagging.

I think I should add this description to the source code ...

Thanks
Berni.