Last week, we took a look at a couple fun but flawed technologies for indoor positioning and wayfinding: echolocation and infrared. The post explained why they both hold promise in certain use cases but don't hold up well for indoor positioning and wayfinding in complex healthcare spaces. The bottom line was that they are both too easily blocked by noise or other factors to be effective in that scenario. Today, we're looking at a third technology in the fun but flawed category: geomagnetic positioning.
The earth’s innards put out some powerful magnetic fields. This powers one of the oldest wayfinding tools, the compass, with a needle always doing its best to point north. Geomagnetic signatures all over the planet tend to be fairly unique to a location, a fact which allows some superpower animals to navigate and migrate over incredibly long distances. Birds, bees, turtles, whales can all read these fields to some extent to help steer them in their travels. We call this ability magnetoreception.
We may lack the superpowers of these creatures, but we can fill in that gap with technology. Geomagnetic positioning is a fairly common technique which leverages magnetometers in devices, to map out a space and later read it to determine the position of a device. This signature is typically quite stable, which lends itself to a fingerprinting solution, which holds some advantages over trilateralization. You can get a refresher on fingerprinting and trilateralization in this earlier post in the series.
Magnetometers are quite common and are included in most modern phones. This is handy for both the measuring of magnetic fields and the ultimate application where the phone can compare what it’s currently recording to the magnetic map. A big advantage here is that no infrastructure is required. None at all. This is particularly useful for locations where red tape abounds when it comes to the installation of new technology.
Outdoors, the magnetic signature doesn’t really vary enough to be incredibly useful, leading to about one kilometer accuracy. Indoors, however, the structure of the building lends it more variability. Variability and stability are two key factors to a successful digital fingerprinting operation. While signal noise doesn’t affect the signature, industrial settings or equipment with an intense magnetic signature, such as MRIs at hospitals, can cause wide ranging impact, plunging the signature into unpredictable chaos.
Accuracy can be a significant issue. Detectable anomalies in the signature are more clear when an object is moving, limiting use for asset tracking, and making for an awkward start to any wayfinding journey. Verticality is also a major issue, as the signature doesn’t change significantly from floor to floor. For these reasons, successful geomagnetic implementations are usually augmented through the use of additional technology to fill in the gaps. This dampens the joy of one of this techniques greater strengths with the lack of infrastructure and easy setup.
While all three of the technologies we've looked at in this blog post and the one from last week, have some cool concepts behind them, the flaws limit the practical application. In the next article we’ll dive into the RF technologies most commonly used for more successful location awareness, bluetooth and WiFi, and then dive into some emerging technologies which could be some real game changers.