INDOOR POSITIONING Positioning Through Walls A joint development program by the Department of Homeland Security and NASA’s Jet Propulsion Laboratory has produced a unique indoor positioning and location solution. POINTER shows great promise for first responder operations and many other applications. by Gavin Schrock, CONTRIBUTING EDITOR Jet Propulsion Laboratory A tragedy in 1999 spurred development of an entirely new type of positioning and location technology. “This project started with the Worchester, Massachusetts, warehouse fire,” said William Stout, program manager for the Department of Homeland Security (DHS) Science and Technology Directorate (S&T). “Six firefighters went in to clear an abandoned warehouse that was on fire to make sure there wasn’t anybody in there, and they got trapped. The team couldn’t find them because they had no idea where they NASA-JPL PROTOTYPE of POINTER base units on a first responder vehicle. The magneto-quasistatic fields they generate can be detected through walls, where were, and they ended up perishing. legacy indoor positioning technologies fail. That is what got DHS started with developing a first responder location tracking technology, Stout said. “Over the years from that point on, we investigated Why Magnetic Fields? many different technologies. My predecessor referred to Ranging can be done in many modes, Arumugam said, and most of these as ‘cocktail solutions’ because they would try not all are based on just the amplitude of the propagating to merge different types of technologies — for example, wave. With traditional radio signal ranging, to compute a GPS and inertial — but none of these panned out.” precise position, techniques mostly use multiple sources of signals, for trilateration or multilateration, as GNSS does. Enter Magnetoquasistatics Research However, signals can be perturbed by objects in their path, This lack of progress changed in 2012 when they connected or experience multipath (signals bouncing off objects), which with Darmindra Arumugam, group supervisor, senior is a pronounced challenge for indoor environments. research technologist and program manager at NASA’s POINTER does not employ radio signals in the fashion Jet Propulsion Laboratory (JPL). Caltech manages JPL of traditional ranging solutions such as GNSS, ultra-wide for NASA. In a complete departure from traditional radio band (UWB), and various beacon systems for indoor signal-based positioning technologies, Arumugam and his positioning. However, Arumugam said POINTER does team had been researching magnetoquasistatics (M/QS). generate a radio signal. This is the foundation for the POINTER System. “The key difference is that we are detecting the field The system consists of fixed or portable transmitters, for in a regime where there is no radio propagation mode. instance, a base unit and controller that can be mounted Therefore, it is more accurate to refer to this as a quasi-on a first responder vehicle outside of a building. The first static field, as opposed to a radio propagating wave,” responders carry a small receiver that the base can locate Arumugam said. with two characteristics: the field’s strength (for ranging) and Arumugam said Earth’s magnetic field is a good example its unique pattern (for lack of a better term) for direction of this. “It penetrates structures very well, we can measure (receivers send position info back to the controller via it 100 kilometers beneath the surface, far above the surface, ISM band LoRa). The controller registers and displays the inside buildings, underwater and so on,” he said. “POINTER position of each receiver. uses the kind of the features that you see in Earth’s magnetic field — we are generating quasi-static magnetic fields. 34 GPS WORLD WWW.GPSWORLD.COM | MARCH 2023
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