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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I’m confused, why not?<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>David Lozzi<o:p></o:p></span></b></p>
<p class=MsoNormal><b><i><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Product Development Manager<o:p></o:p></span></i></b></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Delphi Technology Solutions, Inc.<o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>(978) 988-8007 x204 - <a href="http://www.delphi-ts.com/">www.delphi-ts.com</a><o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
<p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><a href="http://www.delphi-ts.com/blogs/lozzi">Blog</a>
- <a href="http://www.linkedin.com/in/davidlozzi">LinkedIn</a> - <a
href="http://www.twitter.com/davidlozzi">Twitter</a> <o:p></o:p></span></p>
<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p> </o:p></span></p>
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<p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span
style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> David Anguiano
[mailto:fenixxiii@gmail.com] <br>
<b>Sent:</b> Thursday, October 15, 2009 3:30 PM<br>
<b>To:</b> David Lozzi<br>
<b>Subject:</b> Re: [OpenLayers-Users] Geocoding<o:p></o:p></span></p>
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<p class=MsoNormal>2009/10/15 David Anguiano <<a
href="mailto:fenixxiii@gmail.com">fenixxiii@gmail.com</a>><o:p></o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><o:p> </o:p></p>
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<p class=MsoNormal>2009/10/15 David Anguiano <<a
href="mailto:fenixxiii@gmail.com" target="_blank">fenixxiii@gmail.com</a>> <o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal style='margin-bottom:12.0pt'><span style='background:#FFFF33'>but
please do not send Messages to this post, thanks</span><o:p></o:p></p>
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<p class=MsoNormal>2009/10/14 David Lozzi <<a
href="mailto:dlozzi@delphi-ts.com" target="_blank">dlozzi@delphi-ts.com</a>>
<o:p></o:p></p>
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<p class=MsoNormal><o:p> </o:p></p>
<p class=MsoNormal>Hi Paul,<br>
<br>
WOW. Thanks for the insight, I've been wondering... What geocode service do you
use?<br>
<br>
David Lozzi<br>
Product Development Manager<br>
Delphi Technology Solutions, Inc.<br>
(978) 988-8007 x204 - <a href="http://www.delphi-ts.com/" target="_blank">www.delphi-ts.com</a><br>
<br>
Blog - LinkedIn - Twitter <br>
<br>
<br>
-----Original Message-----<br>
From: Paul Spencer [mailto:<a href="mailto:pagameba@gmail.com" target="_blank">pagameba@gmail.com</a>]<br>
Sent: Wednesday, October 14, 2009 5:54 PM<br>
To: David Lozzi<br>
Cc: <a href="mailto:users@openlayers.org" target="_blank">users@openlayers.org</a><br>
Subject: Re: [OpenLayers-Users] Geocoding<br>
<br>
This isn't a direct answer, rather I'm answering why services may be<br>
different and providing some guidance on geocoding based on my<br>
experience. Don't read on if you don't care about that.<br>
<br>
The short answer is that differences in location returned by different<br>
geocoders probably depends more on the data source being used by the<br>
geocoder than the geocoder itself.<br>
<br>
Address parsing aside, geocoding is actually a fairly straight forward<br>
process that probably uses one of two techniques:<br>
<br>
technique 1: linear interpolation<br>
<br>
* find the record that matches the requested street (a lot goes into<br>
identifying the correct street, let's leave that out)<br>
* find a segment of the street with a start and end address that<br>
contain the requested street number<br>
* find a point on the segment equivalent to where the requested number<br>
is between the start and end of the line<br>
<br>
What is typically different here between geocoders (assuming they find<br>
the same street) is the quality of the street number data (is it<br>
there, is it correct, is it the right way around, is it associated<br>
with the correct side of the street for odd/even etc) and the quality<br>
of the geographic line segment that represents the street.<br>
<br>
Some services might also use some heuristic data for adjusting the<br>
interpolated location from being straight linear interpolation to<br>
something (that may be) more accurate.<br>
<br>
technique 2: exact location<br>
<br>
if you have tax lot/parcel/cadastral data then you can find an exact<br>
match on a street address to a parcel associated with that address and<br>
return the centroid of the parcel (perhaps snapped to the appropriate<br>
street segment).<br>
<br>
<br>
The other component of a typical geocoder is its ability to parse an<br>
address and match it to a street segment. This can involve a lot of<br>
complicated steps and has to accommodate a seemingly infinite number<br>
of ways that addresses can be written, missing address components, mis-<br>
spellings of all parts, incorrect information such as incorrect zip<br>
code or wrong street type, and more.<br>
<br>
You need to evaluate geocoders on a couple of parameters:<br>
<br>
* what is the source data they are using and how 'accurate' is it?<br>
<br>
* is it accurate enough for you vs what you are paying for it? (a<br>
commercial data set might be arguably more accurate than a free one<br>
for instance)<br>
<br>
* given how your addresses are expected to supplied, how well does<br>
each service parse the address, accommodate missing, incorrect or mis-<br>
spelled data and ultimately map that to the right address<br>
(disregarding actual accuracy of the address)<br>
<br>
Typically, if you are mapping results of geocoding, you will also want<br>
to ensure the geocoder is using the same source data as for generating<br>
the maps to minimize the visual impact of differences in the quality<br>
of the actual street vector data. In the end, this is usually more<br>
important than the physical accuracy for many use cases.<br>
<br>
Cheers<br>
<br>
Paul<br>
<br>
On 2009-10-14, at 5:21 PM, David Lozzi wrote:<br>
<br>
> Hello,<br>
><br>
> What service are you using to geocode your addresses? I've looked at<br>
> a couple and I've been getting different results per set.<br>
><br>
> Thanks,<br>
><br>
> David Lozzi<br>
> Product Development Manager<br>
> Delphi Technology Solutions, Inc.<br>
> (978) 988-8007 x204 - <a href="http://www.delphi-ts.com/" target="_blank">www.delphi-ts.com</a><br>
><br>
> Blog - LinkedIn - Twitter<br>
><br>
> _______________________________________________<br>
> Users mailing list<br>
> <a href="mailto:Users@openlayers.org" target="_blank">Users@openlayers.org</a><br>
> <a href="http://openlayers.org/mailman/listinfo/users" target="_blank">http://openlayers.org/mailman/listinfo/users</a><br>
<br>
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