Reverse Geocoding

[Cord Thomas]

Stephen's process is pretty much the algorithm i am using in my address
matching project

Cord

Stephen Woodbridge wrote:

> I have a product that does this, see:
>
>    http://imaptools.com/demos1/?tab=4
>
> The algorithm is not too complicated.
> 1) locate a list of line segments based on a lat/long
> 2) find which line segments are closest to the lat/long
> 3) drop a normal to the closest line segment
> 4) compute the ratio of the length from start of line to the projected
> point compared to the total line length
> 5) determine if the lat/long is on the right or left side of the line
> 6) compute the house number from the range of house numbers on the right
> or left and the ratio position of the projected point.
>
> -Steve W.
>
> Camden Daily wrote:
>
>> To the best of my knowledge, mapserver doesn't do any geocoding at
>> all.  The only package I've been able to find that can do it is the
>> Geo::Coder::US perl module from CPAN.  The module has an import()
>> function that can be used to generate a database for geocoding from
>> TIGER/Line data files, and a geocode() function that can then geocode
>> a given address.  I've managed to build my own database and get my
>> PHP/Mapscript to interface with the perl module for geocoding, but
>> reverse would be much trickier.
>>
>> If you don't care much too much about accuracy, it would seem that the
>> same alogorithm used to geocode could be reversed with a little work.
>> If you've got good Perl skills, I'd suggest looking at the source for
>> Geo::Coder:US.
>>


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