GPS, or global positioning system, is a tool that is used to measure distance and to help pinpoint location any place in the world. The fact is that it is an excellent tool that can do so much more than just tell you where you are. And, it is being used in everything from heart rate monitors to automobiles. If you haven¡¦t heard of GPS, you need to get caught up. It could help to benefit your life in one way or another.

First, understand how GPS works. Circling the globe are 24 satellites. They are orbiting the Earth at different locations and make a complete orbit around the Earth in about 12 hours. They are located about 12,000 miles above the surface of the Earth. They correspond with receivers that are scattered around the world. They are always transmitting information through digital radio signals. These signals tells the transmitters where they are and the exact time. They are so precise that they transmit time to the billionth of a second in accuracy.

How They Work

Each of the satellites that work in the GPS network will send these signals to the transmitters down on Earth. They travel at the speed of light in fact. By knowing the length of time that it takes for the signal to get to the receiver, the receivers can get precise measurements. In other words, the longer it takes the receiver to receiver the signal from the GPS satellite, the farther away the GPS satellite is at that moment. This all helps the receiver and the transmitter to convey where they are on a longitude and latitude basis. When four receivers are used, this can also tell the altitude as well.

It was first developed and used by the United States Government in the Department of Defense. It allows for accurate, all weather navigation for such things as military ground, sea and air forces to work and communicate.

Today, though, it is used in much different circumstances. In fact, you will see it used throughout the world in many non governmental rolls.

Today’s Uses

There are many uses of the GPS system today. In many cases, the GPS is a great way for finding and keeping track of just about anything. It has the ability to communicate within seconds and with precision that is unmatched in any other application available. It is also simple to use and inexpensive in many cases as well. Here are some examples to think about.

You may have heard of cars and other vehicles using GPS tracking. This is one of the largest and most beneficial uses for the system. First, it allows for the car to be kept safe. For example, it can help to track a car that has been stolen. It works by transmitting data to the satellite receivers that then are sent to the authorities. The end result is that within seconds, you can know where your car has been taken.

But, that is far from all it can do on a car. In many of today¡¦s cars, there are GPS tracking systems that can be used to help navigate the car. For example, if your system is working, it can tell you how to get from point A to point B without a problem. It will even tell you when you should be turning.

Yet another example of its use in the car is its ability to help in emergency situations. The transmitted information can be sent to the authorities to alert them that you are in trouble. GPS jumps in and helps to find your location. Many vehicles are now being outfitted with this.

But, cars are not the only thing that uses GPS. Any device can be equipped with one if there is a need for it. An example would be the heart rate monitor. Many use these for exercise to let them know when they have reached a targeted rate and how long they are holding it for. Well, how about a watch that is equipped not only to monitor the heart rate, but to tell you where you are running, how long it took you to get from one place to the next and the distance that you just traveled? GPS allows for this!

GPS is a system that is useful and convenient. It allows for many uses and it has a real fit within the world. You¡¦ll find it in all sorts of unique products.

For more information about GPS systems visit

http://www.gps-globalpositioningsystem.net/ .

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GPS, or Global Positioning System, is the latest thing in keeping from getting lost when trekking out to visit your Aunt Louise. Years ago you had to rely on landmarks, your handy compass or the guy at the corner gas station, assuming he knew where everything was. Today for about a hundred bucks you can get a little gadget that will tell you exactly where you are, any place on Earth. By using some basic mathematical calculations and a rather complex system, you can be in the middle of the desert, lost as can be, push a button and have your GPS tell you exactly where you are so that you can hopefully find your way back home.

So what exactly is GPS and how does it work?

GPS is actually a very complex and expensive system but the fundamental concepts of the system are very simple.

The GPS system is a group of 27 Earth orbiting satellites. Twenty-four of them are in operation and 3 are backups in case one fails. The system was originally created for the US military but was eventually opened up to everyone else.

Each one of these satellites, weighing in at about 4,000 pounds, circles the Earth at about 12,000 miles per hour and makes 2 complete rotations everyday. The orbits are arranged so that at any one point in the day 4 of these satellites are visible from any place on Earth.

The complimenting receiver that was created to receive signals from these satellites has the job of locating 4 or more of these satellites, figure out the distance to each and from that information determine where on the planet the receiver itself is located. It then transmits this location back to the person who happens to be in possession of the receiver. The operation is based on a simple mathematical principal called trilateration. To simply explain how this works, let’s say someone tells you that you are 10 miles from Newark, NJ, another person tells you that you are 15 miles from Maplewood, NJ and a third person tells you that you are 20 miles from Woodbridge, NJ. By taking those three facts you can figure out exactly where you are because each radius of each distance when linked together will intersect at only one point. That point is where you are located.

In order to actually do the calculation from space the GPS receiver needs to know 2 things. The location of at least 3 satellites above you and the distance between you and each of those satellites. The reason that only 3 satellites or spheres are needed is because the Earth itself can act as a fourth sphere. The GPS receiver itself works by radio waves which are a kind of electromagnetic energy and travel at the speed of light The receiver can actually figure out how far the signal has travelled by timing how long it took for the signal to arrive from each of the satellites.

In the next article on GPS we’ll go over exactly how this system works to measure distance.

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Michael Russell
Your Independent guide to Global Positioning Systems
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In this second of a three part series we’re going to go over how GPS receivers actually measure distance. A lot of math and science goes into this stuff so sit back and get ready to strain your brain.

At any given time, let’s choose midnight for this example, the satellite begins transmitting a digital pattern called a pseudo-random code. At that same time the GPS receiver begins running that same random pattern. When the satellite’s signal reaches the receiver the pattern transmission will lag a little behind the receivers playing of the same pattern. The length of the delay is equal to the travel time of the signal. The receiver multiplies this time by the speed of light to measure how far the signal actually travelled. We assume the signal travelled in a straight line and this therefore is the distance from receiver to satellite.

In order for this measurement to be able to be made the receiver and the satellite both need clocks that can be synchronized to the nanosecond. In order to make this possible you need atomic clocks, not only in the receiver but in every satellite as well. Atomic clocks cost between $50,000 and $100,000. That makes them a little too expensive for everyday use.

To overcome this cost problem the GPS system has a very clever solution. Every satellite contains an expensive atomic clock but the receiver contains a regular quartz clock which the receiver itself constantly resets. The receiver looks at the incoming signals from four or more of the satellites and compensates for it’s own inaccuracy. Once it calculates the correct time value this will cause all the signals that the receiver is getting from the satellites to align at a single point in space. That is the time value held by the atomic clocks in the satellites themselves. So the receiver sets it’s clock to that time value and therefore has the same time value as all the satellites. Atomic clock accuracy for quartz clock prices. You can’t beat that.

When you measure the distance to four satellites you can draw four spheres that all intersect at one point. Three spheres will intersect even if you’re way off but four spheres will only intersect if you are exactly right. The receiver can calculate the time needed for the spheres to intersect at one point. Based on this it resets it’s clock to match the atomic clocks of the satellites. The receiver does this constantly as long as it is on, which gives it the same accuracy as the atomic clocks in the satellites.

In order for this info to be of any use, the receiver also has to know where the satellites actually are. To do this, the receiver stores an almanac that tells where each satellite is at a given time. Any adjustments that need to be made because of gravitational pull are transmitted to the receivers by the department of the military.

In the last instalment of this series we’ll go over problems with the system, how they can be compensated for and how to use the data itself.

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Michael Russell
Your Independent guide to Global Positioning Systems
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