A new generation of indoor global positioning systems (iGPS) for use with large-scale assemblies in manufacturing offers significant advantages over traditional laser tracking systems and laser interferometers. Advances, like the ability to measure, track, align and inspect multiple assemblies simultaneously and concurrently with measurement resolution better than 50µm (micrometer), while operating within a 360 degree rotary field of view make possible significant cost reductions and improved quality in the manufacturing process. The iGPS technology, acquired from ARCSecond by Belgium-based metrology leader Metris (today Nikon Metrology and a division of Nikon Corporation) in 2005, is the first proven indoor GPS with the accuracy, reliability and utility to support large-scale measurement and metrology-assisted production.
Metris' iGPS works by installing an array of infrared laser-pulse transmitters around objects to be measured, usually large manufactured items such as parts and assemblies for aircraft, automobiles or ships. Sensors pick up the signals from the transmitters, and calculate angle and position based on the timing of the arriving light pulses. An amplifier converts the analog signals into digital pulses, and a receiver converts the pulses into angle data. iGPS network software processes the angle data into highly accurate positional information and then 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 effectively unlimited, the size and shape of the work area can be fully defined by the user.
Data from multiple laser transmitters are triangulated and converted into spatial coordinates. Calculating azimuth and elevation using information received from multiple transmitters enables the iGPS to accurately reconstruct the sensor's x, y and z coordinates with large volume coordinate accuracy better than 200µm.