Although satellite-based navigation systems are the preferred means for establishing location in “open” terrain, they do suffer shortcomings in areas where the satellites are obscured from the receiver, particularly by man-made structures such as buildings. In short, the performance of GNSS receivers cannot be guaranteed indoors or in densely populated “urban canyon” environments. Wi-Fi positioning is a technique that has been developed to overcome these limitations and augment GNSS-based positioning systems in just such areas.

The system, dubbed WPS, was developed in 2005 by Boston-based Skyhook Wireless, exploiting the growing popularity of IEEE 802.11 wireless routers (or Wi-Fi “hotspots”). It uses a database of known fixed Wi-Fi hotspots, and triangulates the position of the receiver based on the relative position and signal strength from each hotspot that can be received. And in suitably populated environments, position fixes accurate to 10-20 metres are possible within a couple of seconds.

WPS is seldom used alone. But smartphones and other mobile devices that combine cellular, Wi-Fi and GNSS technologies can use all three to provide hybrid positioning systems that improve on the performance of each individual technology.

However, such hybrid systems are potentially prey to interference issues between each of the technologies, and the consequences of this can be catastrophic for location-based services that rely on precise positioning information. Exhaustive testing of any hybrid location technology is essential to ensure reliable and accurate operation in the field.

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