Address Matching & Sides of Streets

[imap at chesapeake.net]

Sean,

You can build coding rules for such things, but they are not
100%.  What I do is try to derive a parity (Odd/Even) code by
assigning Odd/Even or Both.

What I do is evaluate both from-to of both left and right side
segment and make the assignment.  If

Left From 100 to 198 = Even
Right From 101 to 199 = Odd
or
Left From 100 to 199 = Both

That rule does not always yield a correct match, but most of
the time, that works.  For example you may have one side or the 
other missing a range for the left or right side.  Sometime you will have
secondary address attributes.. that is dependant on the data
you are working with.  Consider the case of a highrise building,
firm, general delivery, post office boxes and rural/contract routes.

You cannot be guaranteed any real truth for soft or imputed matches,
so is is suggested that you score match candidates with a weight.
All of the component of a input record match are given a confidence
factor depending on what is actually matched.   
The address line is parsed and standardized into it components:

[House Number] [Street Prefix] [Street Name] [Directional Suffix] [Type]

This is just a single permutation, but just and example of how
you might assigned to weight House Number and Street Name, whereas the
direction prefixes, suffix and type carry less weight.   If you derive
a match for a record and only match the Street Name (there is no 
address ranges attributes coded)...  that record still is assigned a weight
and considered a candidate.  In those cases, it is best to resolve a 
ZIP+4 or Census Block centroid to geocode from.  The candidate with the
highest weight is *probably* the best answer, but you need to validate
the City/State or Postal code as well.  In datasets that have large
tiles, (like county), you will see situations where 123 Main St
occurs multiple time within the tile, so you have to make sure the
you at least validate City/State and postal code as well.



Regards,

Chris Stuber (mapsurfer)
Silicon Mapping Solutions, Inc
410-257-3187




Sean O'Hagan wrote:
> 
> Hello list:
> 
> This question is to any mapserver users who have created geocoders out
> there. I've been thinking about it for a bit, and I'm wondering if it's
> possible to determine the side of the street an address is on, given the
> fromleft, toleft, fromright, toright fields for a line. I originally thought
> it was, but now I fear it may not. Can someone confirm this? Thanks very
> much.
> 
> Sean O'Hagan
> Metavera Solutions, Inc.
> 192 Spadina Ave., Suite 405
> Toronto, ON
> M5T 2C2
> Tel: (416) 504-8351
> Fax: (416) 364-2636
> Email: seano at metavera.com