[OSM-talk] Name finder: Where Am I?

David Earl david at frankieandshadow.com
Tue Aug 14 20:53:26 BST 2007

Have you ever been zoomed right in to the map and not sure where you 
are? Now name finder can tell you.

Just click on the "Where Am I" button in the name finder at
and it shows you the location of the centre of the map in context.

As well as the familiar sentence at the top, the main thing is the 
contextual map "target" on the left. It shows up to six nearby places.

The challenge of doing this is two-fold:

Firstly choosing which places out of the sometimes hundreds of 
possibilities. There's a weighting system which scores places according 
to their status (city high, hamlet low), how far away they are, and 
especially whether they are the closest  place of increasing importance 
(so you'll always get the nearest place, whatever it is, but you are 
unlikely to get hamlets further away than towns unless there is nothing 
else to show.

Secondly, positioning the text on the mini-map so it doesn't all clash 
in a horrible mess or go outside the target. At the moment, it adjusts 
the text, but doesn't take account of the blob that represents the 
place. I could do that too, but at the expense of distributing the text 
further away from its location.

It's all written as Ajax Javascript (calling on the namefnder for the 
place details, so it would be easy to incorporate elsewhere).


Experimentally, the current version now recognises UK postcodes and 
tries to look them up. It does this without using a geolocator database 
- it goes to Google to search for the postcode and then tries to extract 
an address from the results, which it then sends to the name finder as 
if you had typed it.

It's surprising quite how many postcodes get a hit this way, but of 
course not all do. I need to do some further work on the address pattern 
matching especially for addresses that don't have numbers in them - you 
may get some peculiar "not found" messages because of this. Of course, 
the street or whatever it determines has to then be on the map to be 
located by name finder,but if it isn't you'll at least see the address I 
thought I was looking for.


I have also now checked in the source code, mainly for safety's sake, 
into the Sites directory of svn, after some tidying up and updating 
comments etc. So if you want to see how it works, it is all there now to 



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