Wednesday, April 14, 2010

Several approaches to do Geolocation by IP address programmatically

Geolocation is the process of identifying the real-world geographic location based on a device’s IP address (either connected through cable or WiFi access point), GSM/CDMA cells IDs or GPS and so on. The result of Geolocation is essentially a pair of coordinate (lat and lon) on earth, and if combined with other service like Geocoding the result can also be translated to a well-known place name or a physical address.
Geolocation by IP address although  may not be as accurate as GPS sometimes, does have great value in many of today’s location aware web applications. One of the typical examples is that when you do search on internet the search engine will detect the location by your IP address and automatically filter and sort the results based on that information. In this article I will be looking at some existing approaches I’ve played with to do Geolocation by IP address.

1. W3C Geolocation API
If you’re in JavaScript environment, W3C Geolocation API is definitely the approach you should follow because it is the standard. Independent of the actual source of the location information which is not just limited to IP address but can also be WiFi and Bluetooth MAC address, GSM/CDMA cell IDs, GPS or so, it actually defines a high-level interface to location associated information with devices hosting the implementation. Other than that W3C Geolocation API also defines the way you request repeated position updates through callback mechanism as well as requesting an aged position.
Mozilla Firefox is a very good example of such implementation. The code example below illustrate the common work flow to get your current location in a JavaScript application:
if(navigator.geolocation) {  
/* geolocation is available */  
navigator.geolocation.getCurrentPosition(
function(position) { // success callback  
//alert(position.coords.latitude + "," + position.coords.longitude);
alert(position.address.city);                
},
function() { // failure callback
// error handling
},
{
// other options
timeout:30000
}
);    
} else {      
// browser does not support Geolocation API
} 
In Firefox’s implementation, it gives you not only the lat and lon value of your location but also gives you the address associated with that coordinate. Under the hood Firefox takes advantage of Google Location Service which I believe provided all necessary infrastructure.

2. Google Geolocation API in Gears
Google Gears Geolocation API implements the same W3c Geolocation interfaces but in a more device independent, location information source independent, and browser independent way. It’s online doc is very good and concise for people who would like to use it in their web application.

3. Google Location Service
Google Location Service is far more than an interfaces that only provides geolocation function, but it’s totally valid to use that as a Geolocation service. Without even realizing, it is definitely behind a lot of its own services like Search and Latitude which sometimes you don’t even realize. It is also backing up many other Geolocation API implementations like Firefox. But unfortunately I was able to find out an explicit native Geolocation service API either in JavaScript or in REST flavor. So it’s probably impossible to directly communication with Google Location Service by feeding an IP address and getting a coordinate back.


4. Other Geolocation by IP service providers
HostIP, mentioned in Andrew Turner’s Introduction to Neogeography, HostIP has the largest free database and service for GeoIP (the term Andrew uses for geolocation by IP address). The best part of HostIP is that it freely distribute it’s database with regular updates. Since I don’t find any information regarding license and term of use for HostIP database I would assume it is in public domain. Programmatically HostIP provides a simple and lightweight RESTful API for people to locate themselves by IP. It doesn’t do much but it’s good at what it does. Because of its REST nature, it is not limited to any program environment except that you might need a proxy in your JavaScript web application. Below is an example:
http://api.hostip.info/country.php
US
http://api.hostip.info/get_html.php?ip=12.215.42.19
Country: UNITED STATES (US)
City: Sugar Grove, IL
IP: 12.215.42.19
http://api.hostip.info/get_html.php?ip=12.215.42.19&position=true
Country: UNITED STATES (US)
City: Sugar Grove, IL
Latitude: 41.7696
Longitude: -88.4588
IP: 12.215.42.19
http://api.hostip.info/?ip=12.215.42.19
[use the URL above for an example - XML too long to paste below]
Finally its website itself provides a simple browser based GUI for people who don’t want to bother coding their own app.

GeoIP: MaxMind has a free GeoIP database and API called GeoLite City. MaxMind and it GeoIP product suite does not have a publicly hosted RESTful service or API for directly use but it allows you to download their database in either binary format or CSV format (mainly for you to load data into SQL database) to host locally. The API for accessing the local database is available in many platforms (C, C#, MS COM, PHP, Java, Perl Python, Ruby etc.). The workflow is to first download the database to local disk and uncompress it, then use any of the API available the query the database. Below is an example I tried out using its Java API:
public void lookupServiceTest() {  
try {
LookupService cl = new LookupService("E:\\projects\\geoip\\geolite-city-database\\GeoLiteCity.dat", LookupService.GEOIP_MEMORY_CACHE);
Location location = cl.getLocation("xxx.xxx.xxx.xxx");
System.out.println(" countryCode: " + location.countryCode +
"\n countryName: " + location.countryName +
"\n region: " + location.region +
"\n regionName: " + regionName.regionNameByCode(location.countryCode, location.region) +
"\n city: " + location.city +
"\n postalCode: " + location.postalCode +
"\n latitude: " + location.latitude +
"\n longitude: " + location.longitude +
"\n metro code: " + location.metro_code +
"\n area code: " + location.area_code +
"\n timezone: " + timeZone.timeZoneByCountryAndRegion(location.countryCode, location.region));
cl.close();
} catch (IOException e) {
System.out.println("IO Exception");
}  
}
GeoIP API is free and open source under GPL/LGPL license, and the GeoLite City database itself is also free under its database license. MaxMind also provides an advanced commercial version called GeoIP City, which is functionally equal to the free one but has more accuracy, different redistribution license and more frequent updates.

1 comment:

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