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Positioning systems will use positioning technology to determine the position and orientation of an object or person in a room, building or in the world. ==Time of flight== Time of flight systems determine the distance by measuring the time of propagation of pulsed signals between a transmitter and receiver. When distances of at least three locations are known, a fourth position can be determined using trilateration. Optical trackers, such as laser ranging trackers suffer from line of sight problems and their performance is adversely affected by ambient light and infrared radiation. On the other hand they do not suffer from distortion effects in the presence of metals and can have high update rates because of the speed of light.〔Position trackers for Head Mounted Display systems: A survey, Devesh Kumar Bhatnagar, 29th of March, 1993〕 Ultrasonic trackers have a more limited range because of the loss of energy with the distance traveled. Also they are sensitive to ultrasonic ambient noise and have a low update rate. But the main advantage is that they do not need line of sight. Systems using radio waves such as the Global navigation satellite system do not suffer ambient light, but still need line of sight. 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「Positioning technology」の詳細全文を読む スポンサード リンク
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