subject: Do you know how your GPS system works? [print this page] Do you know how your GPS system works? Do you know how your GPS system works?
If you ask people to consider their Sat-Nav system, most will think of their car's sat nav system, when really the system in their vehicle or whatever, is only in fact the GPS receiver. This is the part of the whole system which receives a signal, which the electronics in your system then turns into your position.
The term GPS means Global Positioning System. It operates because there is always a minumum of 24 sattelites in various orbits around the earth. At any one time, anywhere on the planet will be able to receive signals from the minimum number needed of 4 sattelites. The system was first developed by the American military in order to enable it's forces to navigate with more precision. However since the mid 1990's it's been available to the public, or at least that section of it that has a GPS receiver.
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The orbit of every sattelite is known, and it's position tracked from earth, and each of the sattelites orbit earth twice a day. All of the sattelites are slaved to each other, and they each simultaneously pulse a transmission containing their precise position, and also the exact moment at which the signal was triggered.
The sattelites, due to their precise orbits, will all be at varying distances from the GPS device in question. This could be your Boat GPS, smart phone, or car's sat nav. Due to the disparity in locality and range, the signals can't all arrive at the exact same moment.Thus when these signals get to your GPS, your GPS will "hear" each individual signal, and so using the delay between every individual message it can then calculate the position of each sattelite , and having obtained this data, then it will compute it's own, and hence your position.
GPS devices, have to obtain messages from 3-4 or more sattelites to ensure that an accurate position is able to be calculated. A clear sight of the sky is imperative to make sure that the signals are unobstructed. Adverse weather conditions can sometimes also affect the quality of the signal. That's why when you utilise a Sat-Nav system the GPS systems manufacturers always advise placing the GPS system with a clear line of sight to the sky whenever possible to enable you to get the best quality signal.
The accuracy claims of all GPS system manufacturers are varied, the majority of sat-nav units are accurate to within a few meters though, again sattelite signal capture times quoted will be different, and "cold" signal acquisition times, i.e. from time of switching on the Global Positioning System can be up to several minutes. It may occasionally be longer, due to a combination of the variables given above.
When using a GPS system to navigate, do not just slavishly follow the directions it gives, but also check to make sure you will be safe in complying with the route offered. I'm sure that we have all seen stories in the news of unfortunatetravelerswhoslavishlyfollowed GPS directions and came to grief. That being said, as long as your GPS unit is properly installed, and you takeits directions as advice, then all should be well.
