Different Types Of GPS Systems
Trying to figure out where you are and how to get to where you are going has to be one of the all-time great challenges for humankind. Positioning and navigation have always been critical, but the processes available always had some shortcomings.
Looking toward the stars and their constellations is one of the oldest navigational systems. The bad news about this ancient system was it could not be used if it was cloudy or daylight.
Sighting "Landmarks" was the other navigational system used in ancient times. The biggest problem with this system was that your range was limited by your line of sight.
There are many varieties of GPS systems on the market today, but far and away the most popular three are used for biking, hiking, and automobile navigation. In principle, there are very few differences between how the three operate.
How GPS Systems Operate
Global Positioning Satellite systems transmit signals to earth that are picked up by receivers that are unable to transmit. Each GPS receiver requires an unobstructed view of the sky and thus they are almost always poisoned outdoors. Sometimes they are unable to perform 100% of the time if placed in dense wooded areas or near tall buildings.
All GPS systems depend on an extremely accurate time reference that is provided by atomic clocks located at the United States Naval Observatory. By having atomic clocks on board, each satellite is able to transmit information concerning its location and current time. By transmitting this information, all of the GPS satellites can synchronize their operation so these repeating signals all arrive at the same instant. When the receiver estimates the distance to at least four GPS system satellites, it then can calculate its position in three dimensions.
There are at least 24 GPS satellites that are broadcasting signals frequently. These satellites orbit the earth every 12 hours.
Accuracy of GPS Systems
The accuracy of any GPS system is almost totally dependent on the quality of the receiver. Most of the hand held models on the market today are accurate within 30 yards. More expensive receivers use a method called differential GPS to obtain much higher accuracy. This method requires an additional receiver that is positioned close by, at a known fixed location. Once this is accomplished the accuracy improves to within one foot. This system is more accurate for stationary locations than moving ones.
This improved accuracy has had a significant effect on the importance of GPS systems and their use. No longer are they just used for navigating boats, planes, cars, and people around the Earth.