What is GPS?

GPS (Global Positioning System) is a satellite-based navigation system interconnected orbit. The satellites were owned by the Department of Defense (Department of Defense) United States that was first introduced from 1978 and in 1994 was put on 24 satellites.
 

In order to determine a person's position would require a tool that serves named GPS receiver for receiving signals transmitted from the GPS satellites. The position on the change to a point known as the Way-point will be as coordinate points of latitude and longitude of the position of a person or a location then the screen on the electronic map.
 

Since 1980, GPS services that were once only for the military need began to open to the public. Interestingly, although satellites are worth hundreds of millions of dollars, but everyone can use it for free.
 

These satellites orbit at an altitude of about 12,000 miles from the earth's surface. This position is ideal because the satellite can reach a wider coverage area. These satellites will always be a position to reach all areas on the surface of the earth so as to minimize the occurrence of blank spots (areas that are not inaccessible by satellite).
 

Each satellite is able to circumnavigate the globe in just 12 hours. Very quickly, so they can always reach your position anywhere on the earth.
 

GPS receiver itself contains several integrated circuit (IC) technology is cheap and easy to use by everyone. GPS is used to various purposes, such as cars, boats, aircraft, agriculture and integrated with a computer or PC.
 

                                    Here are some examples of the GPS receiver
 
GPS Satellite System 

To inform the user position, 24 GPS satellites in orbit about 12,000 miles above us. Moving constantly moving around the earth 12 hours with a speed of 7.000 miles per hour. GPS satellites measuring the energy of sunlight, have a backup battery to keep it running at a solar eclipse or when there is no solar energy. Small rocket boosters on each satellite to orbit the right place.

GPS satellites are owned by the Department of Defense (Department of Defense) America, as for other things:

1. Name is NAVSTAR satellites
2. GPS satellites is the first time in 1978
3. Starting there are 24 satellites from 1994
4. Satellite replaced once every 10 years
5. GPS satellite weighs approximately 2.000 pounds
6. The power of the transmitter is only 50 watts or less

The GPS satellites must always be on the right orbital position to maintain the accuracy of the data sent to the GPS receiver, so it should always be maintained in order to position precisely. Stations have ground control in Hawaii, Ascension Islan, Diego Garcia, Kwajalein, and Colorado Springs. Earth stations are constantly monitoring the position of the satellite orbit and clock sure is always right.

GPS Satellite Signal

Carriers

GPS satellite sends the signal in two frequencies. L1 at 1575.42 MHz with two status messages and pseudo-random code for the purposes of calculating time away. L2 brings use precession 1227.60 MHz with a more accurate due to military purposes.

Power radio signals emitted only ranged from 20-50 Watts. It is relatively very low considering the distance between the GPS and satellites to 12,000 miles. Signals emitted by line of sight (LOS), can pass through clouds, glass but not solid objects such as buildings, mountains.

Pseudo-Random Codes
GPS is used for the public to monitor the frequency of L1 in the UHF (Ultra High Frequency) 1575.42 MHz. L1 signal transmitted patterns will have a certain digital code called pseudorandom. Transmitted signal consists of two parts, namely the code Protected (P) and the Coarse / Acquisition (C / A). 

 Also unique code sent between satellites, allowing each receiver to distinguish between the signals sent by the satellites with other satellites. Some code Protected (P) also randomized, so that can not be accepted by ordinary GPS. Encrypted signal is known as the Anti-Spoofing, which is usually used by GPS special for specific purposes such as the military.

Navigation MessageThere is a weak power frequency signal added at the code L1 which provides information about the satellite orbit, clock corection and other system status.

                                                          HOW GPS WORKS?

Each region on the surface of the earth covered by at least 3-4 satellites. In practice, any new GPS could receive up to 12 satellite channels at once. Clear sky condition and free from obstacles makes GPS can easily capture the signal transmitted by the satellite. The more satellites are received by the GPS, the accuracy will also be higher.

The workings of GPS to logically there are 5 steps:

1. Using the calculation of "triangulation" from satellites. 
2. For the calculation of "triangulation", GPS measure distance using the travel time of radio signals.
3. To measure travel time, GPS needs require a high accuracy. 
4. For the calculation of the distance, we need to know precisely the position and the level of a satellite in orbit.
5. Recently had corrected delay signal travel time in the atmosphere until it is received reciever.

How to send GPS satellite signal
GPS satellites revolve around the earth for 12 hours in a precise orbit and transmit signal his formation to Earth. GPS reciever cut that the information and using the calculation of "triangulation" to calculate the exact location of the user.  

GPS receiver compares the time a signal in send with time signals received. From the information was obtained is unknown how the satellite distance. With a GPS receiver spacing distance calculations can perform calculations and determine the position of the user and display the electronic map.

Display screen GPS Receiver
A GPS receiver must be locked signals from at least three satellites to count 2D position (latitude and longitude) and track movement. If the GPS receiver can receive four or more satellites, it can calculate the 3D position (latitude, longitude and altitude). 

 If it is able to determine the position of the user, then the GPS can calculate other information, such as speed, direction of the destination, point, purpose of travel, distance destination, sunrise and sunset and many more.

GPS satellites send information in a very precession because the satellite using atomic clocks. Existing atomic clocks on satellites road with atomic particles in isolation, which can lead to an accurate clock than the usual hour.

Accurate timing is crucial to determine the accuracy of information our site. Besides the more satellite signals that can be received it will be the precession of the data received by the three satellites sending pseudo-random code and the same time.

Height raises profits in supporting work processes GPS, for us because the higher the more clean atmosphere, so that the less interference and orbit suitable and appropriate mathematical calculations.  

Satellites must fixed in the right position so that the earth station must continue to monitor every movement of the satellite, with the help of radar always precession in check on altitude, and speed position.
 

                                  How to determine the location of the signal?

What is the relationship between the signals transmitted by the GPS satellites to determine location means? The signals sent by the GPS satellites will be used to calculate the travel time (travel time). Time travel is often also referred to as the Time of Arrival (TOA). 

 In accordance with the principle of physics, that can be obtained to measure the distance of time multiplied by the propagation of the signal.

Thus, the distance between the GPS satellites can also be obtained from the principles of physics.  

Each signal transmitted by the satellite will also contain very detailed information, such as satellite orbits, time, and obstacles in the atmosphere. Satellites use atomic clock is the most precise time unit.

In order to determine the position of a GPS in two dimensions (distance), it takes at least three satellites. Four satellites will be needed in order to get location, altitude (in three dimensions).  

Each satellite will transmit the signal to be received by the GPS receiver. This signal will be needed to calculate the distance from each satellite to the GPS.  

From a distance, will obtain coverage radius circle each satellite. Through mathematical calculations are quite complicated, intersection (the intersection) any circle satellite coverage was going to be used to determine the location of GPS in the earth's surface.

                                         BENEFIT of GPS? 

By using GPS, you can mark all the locations you've visited. For example, Hotel Mulia in the way points and the umpteen other places.

Actually, there are many benefits to be had if you know the way point from somewhere. First, you can estimate the distance you want to go with your home location. 
 The latest GPS can estimate your distance to the goal, to estimate the actual length of travel with the speed that you are following.  

Second, the location on the mainland is quite easy to be recognized and identified. However, if you happen to see a very good fishing spots in the middle of the ocean or a place to see a good sunset on a mountain top, how to mark the site so you can return to the site later in the day without getting lost? In times like this that a GPS will show its benefits.

With GPS technology can be used for multiple purposes in accordance with its purpose. GPS can be used by researchers, sportsmen, farmers, soldiers, pilot, adventurer, climber, porter, sailor, courier, lumberjacks, firefighters and people with different interests to enhance productivity, safety, and for convenience.

From some of the above usage categorized into:
 

• Locations 

          Used to determine where the location of a point on the surface of the earth is. 

• Navigation

          Helps you locate any point on earth 

• Tracking

           Helping to monitor the movement of objects

• Helping to map a particular position, and the calculation of the nearest network
• Timing

Can be used as a basis for determining the clock all over the world, because the use of atomic clocks are much more precession compared with regular hours.

No matter your position, in the middle of the ocean, in the middle of the forest, on the mountain, or in the town center. As long as the GPS can receive signals from a satellite directly without hindrance, the GPS will always give you the position coordinate information.  

GPS requires a free viewing area directly to the sky. Obstacles such as trees, buildings, and even window film class V-Kool, can reduce the accuracy of the signal received by the GPS. In fact it is not possible GPS can not receive signals from the satellite at all. 

 GPS also has an additional feature that can provide information for your trip, such as speed, travel time, distance taken, time, and more.

Interconnection Model and GPS
A GPS also has firmware that can be upgraded. Upgrading the firmware is typically provided on the site GPS manufacturer.  

Upgrade the firmware usually use the bundled cables or-also available as accessories. This cable also it can be used to connect the GPS to a computer (either a laptop, PC, or PDA with a little help converters).  

GPS software available for various platforms are also quite a lot. With this software, you can easily download the information from the GPS. 

 Memory of a GPS is relatively limited, so the extra capacity to store information so you have to go to a PC / PDA (which usually has more memory) would be very nice. For hardware GPS communication media other than cable, GPS models are now also equipped with Bluetooth, Infrared.

Based on the physical model of GPS is divided into several types such as models of portable / handheld (size like cell phones), there is a greater (typically mounted on the car / boat), and others to use a special interface to connect to a laptop or PDA (Palm , Pocket PC and Nokia Com-municator).
 

GPS for out-door usually also comes with a protective water repellent and resistant impact. Some of the latest GPS even has a color screen and the ability to provide short-range radio communication (FRS / Family Radio Service).
 

Of course, the more features that are offered on a GPS, the higher the price.
If at any time you want to go to a site you've visited by using GPS. Then, you simply upload the data that you've stored on your computer back to the GPS.  

Furthermore, you will get a recording of your previous trip. The location and track you've visited you will be able to meet back quickly, and of course to minimize the risk of getting lost.

Important Terms
Some of the important terms that are important to know related to GPS:

• Waypoint: The term used by the GPS to a location that has been mark. Waypoint consists of latitude (latitude) and longitude (longitude). A normal waypoint depicted in the form of dots and symbols according to the type of location.

• Mark: Marking a specific position on your GPS. Mark the location of a waypoint, then say you do marking. 
• Route: set of waypoints that you have to go in order and put into the GPS. 
• Track: The direction you are traveling mileage by using GPS. Were usually depicted in the form of lines on the GPS display. 
• Elevation: Terms on GPS to determine heights. There are two types of measuring altitude on the GPS, which uses classical instruments 'barometer' or using satellite calculations.

Height measurements using far more accurate barometer in the air, but it can not work in a vacuum chamber lainnya.Ini aircraft or caused by differences in air pressure in the vacuum chamber with the air pressure outside. Height using satellite measurements would be more accurate in a place like that.

• Bearing: Direction / position you want to go. For example, you want to go to a location in a position that is located in the North, then your bearing is said to have set up North. 
• Heading: The direction of current is being run. For example, on the way to the A position before, you encounter obstacles that must rotate to the South first, then you are heading at the time was the South.