The concept of a navigation system was first proposed around 50years ago. Around 20 years ago, only the Government had access to satellite technology so it amazing that in such a short space of time satellite based technology has made its way into navigation systems and even mobile Phones. You would be hard pressed to find a high or mid-tier phone without a built in navigation system and even some entry level phones (such as the entry level Android phones) come with a ready to use navigation system. Gone are the days when you need to stop and ask for directions but have you ever wondered how your phone determines where you are? Surely the navigation system doesn’t call its friend up and ask it for directions! Does it?
As you read this blog post, a network of GPS satellites are orbiting the Earth at an altitude of about 20,000 KM, making two full rotations around the Earth every day! A few Satellite systems have emerged but only two have made their way into mainstreams phones. At the moment, GPS is more widespread but GLONASS is said to be more accurate due to the way the satellites have been positioned. Many new devices such as the iPhone 4S, iPhone 5, Galaxy S3 as well as the new Sony Xperia phone make use of both GPS and GLONASS satellites to obtain greater accuracy and to shorten location finding times. GPS has 27 satellites and 3 of those are used for backup purposes. Like GPS, GLONASS has 3 for backup purposes as well but only has 24 satellites.
Google Maps on Android
Navigation system on IOS 6
How does it work?
A random number is generated consisting of a long string of data and is continuously broadcasted by each satellite. The contents of the data being transmitted is not important but what is important is that the contents of the data being sent by the satellites and hat being received by the navigation systems is the same.
Your phone compares signals sent from a number of satellites in real-time. Phones use data from 4 satellites since GPS satellites have been positioned so that 4 satellites are able to communicate with a receiver at any given time. Comparing data from 3 satellites is considered to be sufficient but GPS makes use of 4 satellites for additional accuracy.
The phone now knows the distance between itself and the satellites tracking it but doesn’t know in which direction. To do this, it uses trilateration which compares the distance between you and three other locations although GPS uses 4 locations for additional accuracy. If a satellite can see your phone known you must be somewhere in the radius of what that particular satellite can see. If a second satellite can see you then you know that you must also be within the radius of what that satellite can see. However, since two satellites can see you, you know that you must be somewhere where the radius of the two satellites intersects. The introduction of a third satellite can show you exactly where you are.
Now that your phone has your latitude, longitude and altitude it can now compare these coordinates with its own maps in order to determine the details of where you are.
BIO: This is a guest post on behalf of RAM tracking who specialise in vehicle tracking software. Vehicle tracking software uses a similar method to determine where the driver is.
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Source : techtalkafrica[dot]com
