Satellite Navigation Technology

There are only a handful of digital map compilers for Sat Nav systems and for commercial use you have a choice between TeleAtlas and NAVTEQ. They in turn however get much of the basis of their data from the same sources, such as Ordnance Survey in the UK, and then update this data and compile there own additional information known as Points of Interest, or POIs such as hotels and amusement parks.

Digital mapping works by allocating every road a number, name, exact location in the world. Its length and the time it takes to travel it. There are also details of how the road connects to the rest of the network. When you program in that you want to travel from A to B, a maths algorithm calculates a route. It can calculate the shortest distance or the fastest journey time.

As essentially every Sat Nav system is using the same data, the end results will be almost identical which can result in 'rat runs'. Its' some of this additional data that the likes of TeleAtlas and NAVTEQ add that starts to differentiate these routes, flagging up some as being more liable to congestion than others for example.