Several key developments were necessary before GPS could develop into the system that we know and used today on our handheld and adventure GPS. Just before the Second World War scientists needed to measure the oscillation of atomic particles with a precision which was previously impossible. Prior to this time the only way of keeping time was by the swing of a pendulum or the use of the vibration of a quartz crystal inside a watch, accurate to the hundredths of a second but nowhere near enough to further the cause of atomic science. It was only in the 1940s that a team from the Massachusetts Institute of technology was able to develop a process whereby atoms could be beamed through an oscillating magnetic field. The process was further refined in order to resonate the frequency of the atoms with the magnetic field thus creating pulses of time. This atomic clock became instrumental in the development of GPS later on.
In the late 1950s Sputnik became the first ever satellite to orbit the Earth. Again it was American researchers that quickly realised the theoretical usefulness of the satellite in terms of navigational purposes. They calculated, using the Doppler effect, that the radio frequencies of the approaching and departing satellite could be calculated in order to give an exact positioning of the object. Also because the object was 11,000 miles above the Earth its trajectory could be predicted incredibly accurately. With growing knowledge the US military developed its own satellite navigation system in the 1960s and called it the Transit System. Satellites were put into orbit around the poles, and nuclear submarines carrying the Polaris nuclear deterrent were able to take the signals in order to calculate their position beneath the waves.
The Pentagon was unsatisfied with the Transit System of GPS and so convened a meeting in 1973 that proposed what later became known as the Navstar system, a system whereby 24 satellites equipped with atomic clocks would orbit the earth and work together to give a precise position of a given receiver. The company Rockwell International were tasked to build the 24 satellites, each one weighing around 2000lbs and the size of a car. The orbits of the satellites were adjusted so that on every point on earth at least four satellites would be able to work together to send signals enabling exact positional calculation for the receiver.
So it was for the first time that somebody with a relatively simple quartz-powered satellite radio signal receiver could get their position accurately calculated by four satellites working in tandem. Careful monitoring from earth made sure the 24 satellites remained accurate in terms of their atomic clocks and their timings and positioning. This self same technology is the one we use today to power our Garmin, Satmap or Memory Map handheld devices; though born through military innovation and necessity today’s GPS happily can be put to more useful and peaceful means.
These days there are so many varieties of good handheld GPS available with a ton of features to suit your purposes. You can find detailed mapping features, electronic compass, altimeter and barometers and distance/time calculators. It’s amazing how far we’ve come since those early days of GPS.
If you want to know more about the Satmap Active 10 Plus and how to choose a good adventure GPS you should follow these. Thanks for your time.