Auto GPS » Satellite Navigation System

GPS And How It Works

admin — Sun, 17 Jan 2010 22:22:09 +0000

GPS stands for Global Positioning System, a satellite navigation system with twenty-four satellites in orbit. These satellites were put in place by the United States Department of Defense for military uses, and were called NAVSTAR. The first satellite was launched in 1978 and the twenty-fourth and last satellite was finally in place in 1994. In 1980 NAVSTAR was made available to the general public for commercial use.

GPS works 24 hours a day in any weather. The satellites orbit the earth twice a day in a specific orbit that is about 12,000 miles above us. In orbit, the satellites travel as fast as 7,000 miles an hour. As they are orbiting, they transmit information to receivers on earth. The receivers use this information to calculate the user’s location. This calculation is made by determining the difference between the time a transmission was made and when the receiver received it. This is then used to calculate the distance and the position is displayed on the receiver.

For a receiver to calculate a latitude and longitude position is to receive information from three satellites. To calculate latitude, longitude and altitude a receiver must be able to receive information from four or more satellites. After position is known the GPS can then tell the user information about speed, trip distance, the distance to a desired destination, sunrise and sunset times, bearing and other information.

While in orbit, the satellites are powered by solar energy. They also have backup batteries that are used in the event of no solar power such as an eclipse. The energy is used to power small rockets on the satellites that keep them in the proper orbit. At any one time only about 50 watts of power or less is used to transmit information. The satellites are designed to last about ten years, and the U.S. Department of Defense is constantly making and launching replacement satellites. Each satellite is about 2,000 pounds and seventeen feet across when the solar panels are out.

GPS receivers are generally accurate within 15 meters. Other than investing in a receiver there are no fees or other equipment required to access the GPS signal. If very accurate readings are needed, Differential Global Position Systems (DGPS) will provide accuracy within three to five meters. The United States Coast Guard operates the most popular DGPS.

Two power signals are transmitted and are referred to as L1 and L2. The L1 frequency is used for civilian purposes. These signals are relatively low power signals and travel by line of sight, so they can go through clouds, glass, and plastic, but not solid objects like buildings or mountains. In every transmission the satellite sends three types of information, its pseudorandom code, ephemeris data and almanac data. The pseudorandom code is an I.S. code that identifies which satellite the information is being sent from. Ephemeris data tells the receiver where the satellite should be at any time of the day, and almanac data sends information about the status of the satellite, the current date and the time. The almanac data is the part that is essential for determining the user’s position.

By: Chris Simons

GPS Systems Make Life Easier For All of Us

admin — Sun, 17 Jan 2010 10:48:55 +0000

GPS – Global Positioning System is a satellite navigation system. First conceived as navigation aid by the military now number of GPS satellites broadcasts accurate timing signals by radio to GPS receivers.GPS provides a set of coordinates which represent the location of the GPS unit with respect to its latitude, longitude and elevation on planet Earth thus allowing them to accurately determine their location anywhere on the earth at anytime. It has become an important tool for map making and land surveying and is also used for very precise time reference needed for scientific research like the study of earthquakes. GPS receivers come in various formats, from devices integrated into cars, to phones to watches.

The GPS satellites broadcast accurate clock information in two forms:

Coarse Acquisition code/C/A-This is used mainly for civilian navigation which broadcast at 1,023 MHz repeating every millisecond. Each satellite sends a distinct C/A code, which allows them to be identified.

Precise code/ P-code- The P-code broadcast at 10.23 MHz, but it repeats only once per week. The P code is first encrypted into the Y-code, or P(Y), which can only be decrypted by units with a valid decryption key.

Applications of GPS:

There are number of fields where GPS has been used such as:

Military

It plays an important role in the military by helping to find precise targeting of military weapons such as missiles and precision guided munitions. It also provides good location awareness thus helping in controlling of forces and command.GPS satellites also carry nuclear detonation detectors.

Navigation

If you are someone who are likely to always get lost while driving then GPS is what you need in your car. It is used as navigation aid in cars, ships and planes. Hikers and trekkers use hand held GPS receivers to find their way. Even visually impaired people use this GPS equipment to guide their way.

Surveying

Construction workers also use GPS receivers for surveying the land to locate boundaries, structures, and survey markers, and for construction of roads.

Geocaching

GPS receivers are also used in recreational activities like geocaching where a hand held GPS receiver is used. Geocachers use this to travel to specific longitude and latitude walking or hiking to natural locations, searching for particular objects hidden by the other geocachers.
Aircraft passengers

Airline passengers can use GPS units in some airlines inside the aircraft except while landing and taking off as they have very little risk of interference. These airlines integrate aircraft tracking into the seat-back television entertainment system, available to all passengers even during takeoff and landing.

Precise time reference

For accurate time GPS is used. In time code generators GPS is used as a reference clock and also when sensors are deployed they are used to provide accurate time for each recording apparatus. Even atomic clocks are set to GPS time.GPS time is counted in days, hours, minutes, and seconds, in the manner that is conventional for most time standards.

Location-based services

Location based services also use GPS to locate all mobile phones. It provides a location solution is dependent more on mobile phones and less on telecommunications network topology. This also helps to provide specific location information to the mobile phone.

The biggest problem faced in GPS is that the atmospheric conditions can change the speed of the GPS signals while passing through the ionosphere. This effect gets minimized when the satellite is directly overhead and becomes greater toward the horizon.

By: Jeffrey Meier

GPS Auto Navigation System Safety

admin — Fri, 02 Oct 2009 13:04:31 +0000

If you have installed a GPS auto navigation system in your car, then you should follow a few simple rules when driving in order to maximize your safety on the road. It doesn’t matter whether you are a long distance driver using the GPS auto navigation system

to plan the most efficient route possible, or just using your satellite navigation system to find a route around the traffic problems in your home town, the rules for using GPS systems safely are the same.

The first thing to check before you set off on your journey is to make sure that the GPS receiver is firmly mounted. If you have a windshield mounted receiver that uses a suction cup to hold it in place, make sure that it is firmly attached, while if your GPS receiver is mounted on the dash, check it to ensure that it is not going to fall off.

There is nothing worse than the unit falling off its mounting while you are driving, and this is a very dangerous thing to happen, especially if you start to reach around and try to reattach it while you are driving. If your system is removable, you should take it out of the car whenever you leave it parked in order to remove any temptation for thieves who might otherwise try and steal it off you.

Once you have started on your journey, and set the SatNav system up to plan your route, you should not touch it again. The SatNav should be there to assist you, not to distract you. Ideally, it will give you information about directions through the car’s audio system, and you will not need to look at the screen too often when you are driving, as this means that your attention will be diverted away from where it should be – the road.

It is important to remember that the advice given by a GPS auto navigation system is not infallible, and it is not a substitute for common sense. If you feel that you are being misdirected, and the route that you are following is wrong, do not be afraid of ignoring the advice and following an alternative route.

When used properly, and safely, an GPS auto navigation system

can provide you with all the information that you need in order to get to your destinations quickly and easily, with a minimum of fuss, and managing to avoid any traffic problems.
By behaving sensibly with your GPS auto navigation system – making sure it is well fitted, leaving it alone when you are driving, and paying attention when you need to – you will have a safer, quicker and more enjoyable journey than ever before, and never need get lost again.

By: Jason Miller