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Reverse Geocoding code

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100374] Reverse Geocoding code
  • From: "Coleman, Mark" <Mark.Coleman at LibertyMutual.com>
  • Date: Tue, 2 Jun 2009 06:43:19 -0400 (EDT)

Greetings,

Periodically I use Mathematica to help with geospatial analysis. Recently,
Google Maps added the ability to reverse geocode an address, that is,
translate a human readable street address into the corresponding
lat-long coordinates (within a reasonable degree of specificity). Here
is some Mathematica code to do this:


 reverseGeoCode[{lat_,long_},outputType_]:=
Module[{apiKey,baseURL,qAddress,qAddressFinal,finalURL,geoRes},
   apiKey="PUT YOUR KEY HERE";
   baseURL="http://maps.google.com/maps/geo?";;
   qAddressFinal=StringJoin[ToString[lat],",",ToString[long]];

finalURL=baseURL<>"q="<>qAddressFinal<>"&output="<>outputType<>"&"<=
>"key
="<>apiKey;
   geoRes=ToExpression["{"<>Import[finalURL]<>"}"];
   geoRes
  
   ];

This essentially involves converting the lat-long code to a string, then
composing the appropriate URL to invoke the Google web service. This is
trivial in Mathematica (I'm running v7) and, in my experience, a great way to
highlight the power of Mathematica to my business colleages (when I'm not
rotating a 3-d graphic for them!)

Please note that in order to run this code, you need to have a
Google-issued API Key (I've removed my key from the above code -- just
replace it with yours). The keys are free and give you access to
Google's online web services. I've found that performance is generally
pretty good, thought Google does place a limit on how many times you can
call this service during a 24 hour period (the number is around 5000 per
IP Address). So if you have a large number of addresses to reverse
geocode, this may not be the most efficient way to do so. Also, this
works quite well for U.S. lat-long coordinates. I have not tested it for
other countries.

As an example:

In[72]:= computeLatLong[{"100 Trade Center Drive", "Champaign", "IL"
,"61820-7237"}, "csv"]

Out[72]= {200, 8, 40.0971, -88.2456}



For information the Google Maps API, please see:
http://code.google.com/more/#products-geo-maps


Cheers!


Mark S. Coleman
Claims Research & Development

Personal Market Claims
Mark.Coleman at libertymutual.com
Boston: (617) 654-4572  SDN: 8-654-4572
Portsmouth: (603) 245-5003
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