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WhereAmI Location Service - Documentation How it works Currently, WhereAmI uses three different methods to determine your location. The design of these current methods focuses on providing a location determination service without the need for client specific assistance. Future enhancements to the service will include the ability for hosts to augment the information, such as with a client-based GPS. Association Events For users of the Georgia Tech LAWN, WhereAmI captures the associate and dis-associate records from the 1300+ access points on the GT campuses. Using these events, WhereAmI determines which AP you are currently associated with. From a database with the geographic coordinates of the APs, the service estimates your location to around 50 meter accuracy. There are a few shortcomings to this method. One issue is that the access point your device is currently associated with may not be the one that is physically closest to you. With the high density of APs in most campus buildings it is common that you will be able to see several APs at the same time. Also, for most buildings, the AP database does not currently have a precise latitude and longitude within the building. Instead, only a building location is recorded. If you have more accurate location information for the APs or have found an AP that is showing up in the wrong location please contact us. Finally, since only location indication using this technique is the associate and disassociate events, it is difficult to determine with a 100% certainty that a device is still in the same location. Thus these locations are specified in time spans to indicate that the location was known from the time of the association to the disassociation. It is occasionally possible for a device to drop off the network without causing an explicit disassociate event. This device will appear to still be in the last known location indefinitely. Thus the location is only known with certainty immediately after an association event. Location Appliance In a limited number of buildings on the GT campus the wireless network is supported by a Cisco Location Appliance. This device provides specific location calculation above and beyond the AP association information being used elsewhere on campus. This device is currently in operation in the Klaus and Rich buildings. IP Address As a last resort, it is often possible to determine an approximate geographic location based simply on an IP address and where it is registered. For GT addresses, this determination is made based on the subnetwork allocation. For non-GT addresses, an external service is used. There are several commercial services maintained today, for instance to support location dependent advertising, that use this technique to reliably determine a city. However, most of these are pay-per-user services that are not suitable for this research. Currently, WhereAmI is using the NetGeo service from CAIDA. This service is not currently updated. If you are interested in improving on this database please contact us. Third Party Location Lookups One of the newest features of WhereAmI is the support for third-party lookups. This feature allows you to view the location of others through a tightly controlled permission system. All users must authenticate with the service to query location information. Users can grant visibility of their location to others and control the accuracy of the data that is shared. Privacy With first party lookups, you can only retrieve the location of the device from which you are sending a query. It is not possible to use this service to determine the location of another device. In this way, no other user can determine your location. With third-party lookups, other users can only see your location if you specifically grant them access. The actual location determination databases are not directly accessible from outside the WhereAmI system. Future improvements The WhereAmI project is an ongoing research program with several continuing efforts. One such effort is to add a SIP-based location service for IMS. Another area is to extend the calculation services to support additional techniques including cellular radio calculation and device-augmented calculation. Programming If you are interested in creating a program to use the WhereAmI API please see the programming resources page. |