MENTION the term GPS to Joe Public and he will associate it with in-car devices that read satellite signals to provide driving directions. However, 'indoor' GPS is now being used by many manufacturers to perform large scale measuring and alignment tasks. Instead of satellites this form of GPS functions by installing a series of infrared laser-pulse transmitters located around the object component or assembly. Typically these objects are large manufactured items such as parts and assemblies for aircraft, cars or ships. Sensors receive the signals from the transmitters and calculate position and angle based on the timing of the arriving light pulses. An amplifier converts the analogue signals into digital pulses and a receiver converts the pulses into angle data. Software is used to processes the angle data into accurate position information and makes this information available to the client network, whether on the shop floor or off-site. Because the number of transmitters that can be used is practically unlimited, the size and shape of the work area can be entirely defined by the user. For large assemblies, more transmitters mean that measurement and alignment can be performed accurately without having to move or re-set equipment. This flexibility is the key to the utility of this technology.
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