GPS Systems

GPS, or Global Positioning System, is exactly what the name implies: a global positioning system. GPS systems use radio waves and satellites to determine global location. Since 1994, a constellation consisting of twenty-four global positioning satellites has been in place in space. Each satellite circles the Earth twice on its own orbit, which is about twelve thousand miles from Earth. Using basic science, these satellites are used to find a specific location on Earth.

The Science Behind GPS

Without getting too scientific, the easiest way to conceptualize how GPS works is by the formula you learned back in high school: velocity times time equals distance (VT=D). The satellites orbiting around earth send out radio waves. These radio waves travel at approximately the speed of light, and thus, the speed of light is the velocity for the equation.

The radio waves are sent at a specific time and the time it takes for the radio waves to reach the receiver is recorded as the time in our equation. From these two figures, the distance between the satellite and the receiver can be calculated. This distance is calculated between the receiver and four different satellites and, from these distances, the receiver's location can be pinpointed.

Possible Problems

There are, of course, a few factors that can make the scientific calculations involved with global positioning a bit more complicated. First, the speed of light is not a constant unless it is in a vacuum. Different particles and other atmospheric conditions can result in the slowing of the radio wave's velocity.

Different Earth objects can also affect the accuracy of positioning calculations. The signal that is sent down to Earth from the satellites can bounce off of large objects near the receiver, such as a tall building. This will affect the time it takes for the signal to reach the receiver, and thus affect the time portion of the calculation.

In addition, the Department of Defense, which monitors the position of the satellites, cannot keep track of every satellite's position every second of the day. So, the satellites' positions could vary slightly from what is on record.

GPS systems also pick out different satellites to use for each positioning calculation. The choice of satellites can affect the accuracy of the calculation greatly. If the satellites it chooses are too far from one another, the positioning calculation will be much more accurate than if the satellites are in close proximity to one another.

Where GPS Systems are Used

Today, GPS systems can be found almost anywhere, from farm equipment to laptops. One of the most popular global positioning products, however, is used in the car. These GPS systems assist drivers as they try to find their destination on the next block, in the next city, or in some state across the country. Most of these GPS systems have voice assisted directions along with a map to guide drivers. Many also have information about restaurants, gas stations, and popular tourist destinations built-in. This allows a driver to search for what he or she is looking for, even without an address.