I've used a couple: * http://geocoder.us - based on US Tiger/Line, for fee service or you can get the source and build your own
* http://imaptools.com/geocode-us.html - based on US Tiger/Line, buy a license We are using navteq street data now for our maps and geocodes against Tiger/Line don't align well so we currently have a home-grown solution using imaptools address parser and our own postgis database. There is some indication that PAGC (http://www.pagcgeo.org/) will become more generic, supporting multiple back ends and datasets in a cleaner way. I would probably go with PAGC if that happened. Cheers Paul On 2009-10-14, at 7:09 PM, David Lozzi wrote: > Hi Paul, > > WOW. Thanks for the insight, I've been wondering... What geocode > service do you use? > > David Lozzi > Product Development Manager > Delphi Technology Solutions, Inc. > (978) 988-8007 x204 - www.delphi-ts.com > > Blog - LinkedIn - Twitter > > > -----Original Message----- > From: Paul Spencer [mailto:[email protected]] > Sent: Wednesday, October 14, 2009 5:54 PM > To: David Lozzi > Cc: [email protected] > Subject: Re: [OpenLayers-Users] Geocoding > > This isn't a direct answer, rather I'm answering why services may be > different and providing some guidance on geocoding based on my > experience. Don't read on if you don't care about that. > > The short answer is that differences in location returned by different > geocoders probably depends more on the data source being used by the > geocoder than the geocoder itself. > > Address parsing aside, geocoding is actually a fairly straight forward > process that probably uses one of two techniques: > > technique 1: linear interpolation > > * find the record that matches the requested street (a lot goes into > identifying the correct street, let's leave that out) > * find a segment of the street with a start and end address that > contain the requested street number > * find a point on the segment equivalent to where the requested number > is between the start and end of the line > > What is typically different here between geocoders (assuming they find > the same street) is the quality of the street number data (is it > there, is it correct, is it the right way around, is it associated > with the correct side of the street for odd/even etc) and the quality > of the geographic line segment that represents the street. > > Some services might also use some heuristic data for adjusting the > interpolated location from being straight linear interpolation to > something (that may be) more accurate. > > technique 2: exact location > > if you have tax lot/parcel/cadastral data then you can find an exact > match on a street address to a parcel associated with that address and > return the centroid of the parcel (perhaps snapped to the appropriate > street segment). > > > The other component of a typical geocoder is its ability to parse an > address and match it to a street segment. This can involve a lot of > complicated steps and has to accommodate a seemingly infinite number > of ways that addresses can be written, missing address components, > mis- > spellings of all parts, incorrect information such as incorrect zip > code or wrong street type, and more. > > You need to evaluate geocoders on a couple of parameters: > > * what is the source data they are using and how 'accurate' is it? > > * is it accurate enough for you vs what you are paying for it? (a > commercial data set might be arguably more accurate than a free one > for instance) > > * given how your addresses are expected to supplied, how well does > each service parse the address, accommodate missing, incorrect or mis- > spelled data and ultimately map that to the right address > (disregarding actual accuracy of the address) > > Typically, if you are mapping results of geocoding, you will also want > to ensure the geocoder is using the same source data as for generating > the maps to minimize the visual impact of differences in the quality > of the actual street vector data. In the end, this is usually more > important than the physical accuracy for many use cases. > > Cheers > > Paul > > On 2009-10-14, at 5:21 PM, David Lozzi wrote: > >> Hello, >> >> What service are you using to geocode your addresses? I've looked at >> a couple and I've been getting different results per set. >> >> Thanks, >> >> David Lozzi >> Product Development Manager >> Delphi Technology Solutions, Inc. >> (978) 988-8007 x204 - www.delphi-ts.com >> >> Blog - LinkedIn - Twitter >> >> _______________________________________________ >> Users mailing list >> [email protected] >> http://openlayers.org/mailman/listinfo/users > > _______________________________________________ > Users mailing list > [email protected] > http://openlayers.org/mailman/listinfo/users _______________________________________________ Users mailing list [email protected] http://openlayers.org/mailman/listinfo/users
