1. A method performed by one or more computer systems coupled to a packet-based network via wired or wireless connections to associate geographical location information with IP addresses, the method comprising: receiving a first plurality of advertisement (ad) requests from the packet-based network, each respective request among the first plurality of ad requests including location components of an associated mobile device, the location components including at least a portion of an IP address, a set of geographic coordinates, a name for a geographical region, and a code for a geographical region; selecting a second plurality of ad requests from the first plurality of ad requests, each request of the second plurality of ad requests including a first IP address and having a set of geographic coordinates that meet a first set of predefined criteria; deriving geographical location information for the first IP address using geographic coordinates in the second plurality of ad requests; and storing the geographical location information together with the first IP address in a storage device accessible by the one or more computer systems.