geolocation - How does IP geolocating work?

Question

I'm not looking for a service that does this. I'm just curious as to how geolocation works.

Answer 1

Mapping IP addresses to geolocations is done via tables, where an IP maps to a particular location. This location, however, does't need to be accurate, since IP addresses don't carry any information about their locations, these are approximated.

From http://en.wikipedia.org/wiki/Geolocation_software:

The primary source for IP address data is the regional Internet registries which allocate and distribute IP addresses amongst organizations located in their respective service regions:

• American Registry for Internet Numbers (ARIN)
• RIPE Network Coordination Centre (RIPE NCC)
• Asia-Pacific Network Information Centre (APNIC)
• Latin American and Caribbean Internet Address Registry (LACNIC)
• African Network Information Centre (AfriNIC)

Secondary sources include:

• Data mining or user-submitted geographic location data. For example, a weather web site might ask visitors for a city name to find their local forecast. Another example would be to pair a user's IP address with the address information in his/her account profile.
• Data contributed by internet service providers.
• Merging databases from different suppliers.
• Guesstimates from adjacent Class C range[2] and/or gleaned from network hops.

Accuracy is improved by:

• Data scrubbing to filter out or identify anomalies.
• Statistical analysis of user submitted data.