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
Posts Tagged ‘U S Department’
Keeping Track of Your Kids With GPS
December 3rd, 2009
One great benefit of technology has been global positioning systems or GPS. These systems use satellites to track the whereabouts of people anywhere on planet Earth. They are small units that can be installed many places such as watches, backpacks, cars and even cell phones. Because GPS units are so small they can be used very effectively to as GPS kids tracking devices.
Parents use GPS tracking to keep tabs on the location of their children. Children can be tracked with GPS using their cell phones, watches, backpacks and even attached to their clothing or shoes. No matter where a child is they can be located with a GPS device. Children’s GPS devices are like an insurance policy to help keep your kids safe.
Currently there are a number of satellites orbiting the Earth that were placed by the U.S. Department of Defense. GPS tracking technology makes use of these satellites for both navigation and tracking purposes. The satellites send out an encoded signal that are received by the tracking units and then decoded. The satellites are always sending this signal and the GPS devices can use this signal to locate anything or anyone and their exact position on the Earth within several yards.
GPS tracking services can be purchased from several different companies. Tracking children with GPS is very simple to get started with. All you need to do is purchase a GPS tracking device, have it programmed for your service and attach it to the child in some way. Each GPS tracking company does charge a fee for their service and it varies for each one so do some research first to find out which company can provide the features you want at the lowest cost.
You can subscribe to different tracking plans from several trackings per month to unlimited real time tracking. The only difference between the different plans is the cost with the unlimited and real time versions being the most expensive.
There are also several ways to retrieve your tracking information. Some companies will provide the information via cell phone while others have websites that you can go to to do the tracking or even software that needs to be installed on your PC. In addition, you can receive tracking reports to get all the details of where your child has been. This can be a good addition for teens who are driving.
The biggest negative to tracking kids with GPS is the cost. The GPS devices start around $150 each and the tracking services will run you anywhere from $25 to $100 per month depending on the features you desire.
Children’s GPS tracking systems are a great way to give you added peace of mind knowing that your children can be located at anytime and anywhere they might be. While older children may have some reservations at being tracked, younger children often do not even need to know about the tracking device. GPS kids tracking is not a substitute for parental supervision, but it is a great tool to help us keep tabs on our children and provided added security in our dangerous world.
By: Steven Walters
