Outdoor Positioning Systems
We have all become very used to the idea that a phone or car can know where it is using GPS or one of the equivalent satellite based positioning systems. And it gets better all the time. Modern chips can get you down to centimetres under ideal conditions.
But we have also all had the experience when we go indoors and the position information disappears.
So is there a solution for that?
Indoor Positioning Systems
It turns out there is. Or at least, there are quite a few. They all have their drawbacks and most require you to add technology to the indoor area to get it working. Lets do a quick survey to see what Indoor Positioning Systems are out there.
The first one is using GPS indoors. If you have a high enough roof you can put a GPS repeater on it and project the satellite reception into the building and suddenly GPS works inside the building. We use exactly this technique when needing to test a GPS device inside our building. See GPS Repeaters for one example product.
This covers a very wide range of technologies, of which Bluetooth Beacons are the current industry trend. And they can work either way. You can wear the beacon and the receiver tracks you and uses your RSSI to calculate your position, or you have the receiver and monitor the beacons to achieve the same result.
Increasingly these systems are being used for applications like tracking patients in hospitals and residents in retirement villages.
WPS WiFi Positioning System
You have a WiFi network, so you can use the network as a WiFi Positioning System or WPS. This is similar to the Radio Beacon system and uses the RSSI from your device to the WiFi Access Points.
This uses Inertial Navigation components to keep track of your distance and direction from a known point. It is usually used in conjunction with another system such as GPS outdoors and Dead Reckoning in tunnels to keep an accurate estimate of a vehicles position on a map. And low cost MEMs based devices are now available to provide Inertial Navigation readings.
The weakness is the double integration of the signals leads to noise accumulation and the accuracy of the position estimate decreases over time.
These vary a lot. From a sea of emitters overhead to give a location grid to emitters firing down row and aisles in warehouses and even corner emitters firing angle encoded signals picked up and decoded using sine rule mathematics.
The image above is a system we design in 2006 to do angle based IR location detection in GPS blind spots for container handling equipment. This was capable of locating equipment to within 0.5m.
Time of Flight
This allows you to more accurately work out the distance from the emitter to the receiver but requires very precise timing in both.
Magnet Field Monitoring
This is an obvious one, but most modern smart phones have a compass in them. They usually aren’t a very good compass and that can make this option not viable. However if you do have a good enough compass, you can use local distortions on the magnetic field due to steel structures in a building to estimate your location.
Indoor Position Conclusion
And of course, you can use a combination of the above to meet the specific requirement you have. As usual, the classic trade offs apply. These are:
- battery life
For some addition insights check out 10 things you need to know about Indoor Positioning.
Successful Endeavours specialise in Electronics Design and Embedded Software Development, focusing on products that are intended to be Made In Australia. Ray Keefe has developed market leading electronics products in Australia for more than 30 years. This post is Copyright © 2016 Successful Endeavours Pty Ltd.