![]() There are quite a few reasons GPS might be inaccurate or slow. Or realising that Google Maps doesn't quite have the blue dot in the right place. We've all been there at the start of a run, waiting for GPS to lock on, looking for satellites. The actual information transmitted includes an ID code for the satellite, the current date and time from the satellite's atomic clock, the status of the satellite and orbital info that shows where the satellite (and the rest of them) will be at any given time.Īnd as you'll probably realise, once you've got an accurate GPS signal, it can be used to accurately track running speed, distance to a destination, sunrise and sunset. It's worth noting that GPS has its own control and monitoring stations - four around the world. Outdoors, standard GPS receivers, for instance, are accurate to within 15 metres.Īs well as harnessing GLONASS satellites and using parallel receivers for higher accuracy, wearables and watches can also use WAAS (Wide Area Augmentation System), which can get your location down to within 3m or DGPS - Differential GPS, which corrects GPS signals down to a range of 3 - 5m using a series of beacons. So while GPS is actually very accurate, even in dense cities, it doesn't work indoors - a first world problem tech like iBeacons is trying to rectify. ![]() So that means it won't go through solid buildings but it will pass through clouds and glass. GPS works 24/7 in all weather conditions, though the actual low power 1575.42Mhz radio signal travels by line of sight. Michibiki is Japan's own GPS system, which Casio's upcoming Android Wear smartwatch will support. A rival system named GLONASS uses 24 Russian Aerospace Defence Forces satellites - some smartphones and wearables include both receivers to increase the chances of your precise location being detected and speed the whole sending signals and measuring distances process up by as much as 20%. The GPS satellites aren't actually alone up there. It repeats this distance and time lag measurement for further satellites in relation to the receiver (you) and can then work out your exact position and track this as you move. ![]() What is trilateration? Essentially, the receiver in your smartphone or running watch takes the time the signal was sent from the satellite and the time the receiver receives it and uses that difference to work out how far away the satellite is. ![]() At any one time a receiver needs to detect at least three satellites for latitude and longitude and four satellites to add your altitude. So how do satellites in space work out whether you're on Brewer Street or Frith Street? Well, each satellite orbits the earth in a very precise path twice a day and sends microwave signals to GPS receivers, which take this data and use triangulation to determine your exact location. ![]()
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