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Time of arrival (TOA or ToA), sometimes called time of flight (ToF), is the travel time of a radio signal from a single transmitter to a remote single receiver. Compared to the TDOA technique, ''time of arrival'' uses the absolute time of arrival at a certain base station rather than the measured time difference between departing from one and arriving at the other station. The distance can be directly calculated from the time of arrival as signals travel with a known velocity. Time of arrival data from two base stations will narrow a position to a position circle; data from a third base station is required to resolve the precise position to a single point. Many radiolocation systems, including GPS, use ToA. ==Ways of synchronization== As with TDOA, synchronization of the network base station with the locating reference stations is important. This synchronization can be done in different ways: * With exact synchronous clock on both sides. Inaccuracy in the clock synchronization translates directly to an imprecise location. * With two signals which have different frequency, hence different speed. Sound ranging to a lightning strike works this way (speed of light and sound velocity). * Via measurement to or triggering from a common reference point. * Without direct synchronisation, but with compensation of clock phase differences, 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「time of arrival」の詳細全文を読む スポンサード リンク
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