Radiolocation

It generally refers to passive, particularly radar—as well as detecting buried cables, water mains, and other public utilities.

AOA information may be combined with distance estimates from the techniques previously described to establish the location of a transmitter or backscatterer.

Refraction is important at long ranges (tens to hundreds of kilometers) due to gradients in moisture content and temperature in the atmosphere.

TOA and AOA measurements are also subject to multipath errors, particularly when the direct path from the transmitter to receiver is blocked by an obstacle.

Time of arrival measurements are also most accurate when the signal has distinct time-dependent features on the scale of interest—for example, when it is composed of short pulses of known duration—but Fourier transform theory shows that in order to change amplitude or phase on a short time scale, a signal must use a broad bandwidth.

However, several jurisdictions now allow ultrawideband transmission over GHz or multi-GHz bandwidths, with constraints on transmitted power to minimize interference with other spectrum users.

UWB pulses can be very narrow in time, and often provide accurate estimates of TOA in urban or indoor environments.

Radar systems often use a combination of TOA and AOA to determine a backscattering object's position using a single receiver.

The location of the Caller or handset can be determined several ways: The first two depend on a line-of-sight, which can be difficult or impossible in mountainous terrain or around skyscrapers.

CDMA networks such as Verizon Wireless and Sprint PCS tend to use handset-based radiolocation technologies, which are technically more similar to radionavigation.

Composite solutions, needing both the handset and the network include: Initially, the purpose of any of these in mobile phones is so that the public safety answering point (PSAP) which answers calls to an emergency telephone number can know where the caller is and exactly where to send emergency services.