Today, location determination is most often done by GPS. Chips are now low enough in cost to be incorporated into consumer items. However, GPS has a number of limitations, including having a low signal strength at the ground, which leads to problems of potential jamming and poor or non-existent operation indoors. GPS has really come to dominate the world of positioning - wherever it works.

There are many potential alternatives to GPS in principle, but all without exception have issues which prevent them from being a direct substitute today. The alternatives to conventional GPS include augmented systems, such as Assisted-GPS. But although A-GPS has higher sensitivity it still needs some GPS signal. Other location technologies are based on existing communications infrastructure such as the cellular, Wi-Fi or broadcast systems. These have imitations for location determination as they were not designed for this purpose.

There are also non-wireless approaches such as inertial navigation, which is popular in the transport sector, and can use small, low cost sensors produced by integrated MEMs technology. These devices detect movement and derive location by dead reckoning. For the case of a tethered wireless device, such as a femtocell access point, there also exists the possibility of identifying its position by virtue of where it is connected to the broadband network.

Quotient has undertaken major assignments in this area.

• For Ofcom, a very detailed study evaluating methods of locating wireless devices where GPS satellite coverage was not available or insufficiently accurate. The objective was to identify how wireless devices could determine their location in places, such as indoors and urban canyons, where GPS is unable to operate. It was necessary to investigate conditions where GPS accuracy could be compromised, such as via multipath and to incorporate the evolution in GNSS expected from later systems such as Galileo and GLONASS. Results were presented to telecommunications standards groups looking at geolocation for wireless devices and at the Royal Institute of Navigation annual conference.
• Via the Technology Strategy Board Informed Personal Travel initiative, we developed an analysis of the communications and wireless location challenges of enabling user accessible status information in a demand responsive transport pilot deployment. Options were evaluated for when both GPS (location) and GPRS (data) were not available.