Gps User Manual Working Receivers
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The Global Positioning System (GPS) is a satellite-based navigation system made up of a network of regarding 18-24 satellites placed into orbit. GPS was in the first place intended for military applications, but in the late 1970s, the government made a system available for civilian use. GPS works in any weather conditions, anyplace in the world, 24/7. There are no cost for the use. How it works GPS satellites circle the world twice a day in the same orbit and transmit signal info to down to mother earth. GPS take this info and use triangulation to calculate the user's precise location. The GPS receiver compares the time a signal was transmitted by a satellite with the time it was received. The time divergence tells the GPS receiver how far away from the satellite it is. Now, with this distance measurements from a few more satellites, the receiver may determine the user's position and display it on the unit's electronic map. A GPS receiver will have to be locked on to the signal of at least three satellites to calculate a 2d position (latitude and longitude) and track movement. With four or more satellites in view, the receiver may determine the user's 3D position (latitude, longitude and also altitude). Once the user's position has been determined, the GPS unit may calculate other information, such as speed, track, trip distance, distance to destination, sunrise and sunset time and a lot more. How precise is GPS? Today's GPS receivers are exceedingly accurate, thanks to parallel multi-channel design. Garmin's 12 parallel channel receivers are quick to lock onto satellites when basi turned on and they maintain strong locks, even in dense foliage or urban settings with tall houses. Certain atmospheric constituents and other origins of error may affect the accuracy of GPS receivers. Garmin® GPS receivers are exact to 15 meters on average. The GPS satellite system The 18-24 satellites that make up the GPS space segment are orbiting the world in regards to 12,000 miles above us. They are perpetually moving, making two finish orbits in less than 24 hours. These satellites are travelling at speeds of roughly 7,500 miles an hour. GPS satellites are powered by solar energy only. They have backup batteries onboard to keep them running in the event of a solar eclipse, when there's no solar power. Small rocket boosters on each satellite keep them flying in the rectify path. o The basi GPS satellite was launched in early 1978. o A full constellation of 24 satellites was achieved in late 1994. o Each satellite is built to last regarding 10-15 years. Replacements are perpetually being built and launched into orbit. o A GPS satellite weighs approximately 1,500 pounds and is in regards to 16 feet all over with the solar panels extended. o Transmitter power is only 50 watts or less. What's the signal? GPS satellites transmit two low power radio signals, indicated L1 and L2. Civilian GPS uses the L1 frequency of 1575.42 MHz in the UHF band. The signals travel by line of sight, meaning they will pass through clouds, glass and plastic but will not go through most solid objects such as buildings and mountains. A GPS signal holds three dissimilar bits of selective information -- a pseudorandom code, ephemeris selective information and almanac data. The pseudorandom code is plainly an I.D. code that identifies which satellite is transmitting information. You may view this number on your Garmin GPS unit's satellite page, as it identifies which satellites it's receiving. Almanac data, which is perpetually transmitted by each satellite, holds important info regarding the status of the satellite (healthy or unhealthy), current date and time. This portion of the signal is necessary for a good position view. Sources of GPS signal errors Factors that may degrade the GPS signal and thence affect accuracy include the following: o Ionosphere and troposphere delays -- The satellite signal slows as it passes through the atmosphere. The GPS scheme uses a built-in model that calculates an intermediate amount of delay to partially rectify for this type of error. o Signal multipath -- This occurs when the GPS signal is reflected off objects such as tall buildings or big rock surfaces before it reaches the receiver. This increments the travel time of the signal, thereby causing errors. o Receiver clock faults -- A receiver's built-in clock is not as precise as the atomic clocks onboard the GPS satellites. Therefore, it may have very slight timing errors. o Orbital errors -- Also known as ephemeris errors, these are inaccuracies of the satellite's reported location. o Number of satellites visible -- The more satellites a GPS receiver may "see," the better the accuracy. Buildings, terrain, electronic interference, or now and then even dense foliage may block signal reception, causing position errors or perchance no position reading at all. o Satellite geometry/shading -- This refers to the relative position of the satellites at any given time. Ideal satellite geometry exists when the satellites are located at wide angles relative to each other. Poor geometry results when the satellites are located in a line or in a tight grouping. o Degradation of the satellite signal -- Selective Availability (SA) is an intentional degradation of the signal once enforced by the U.S. Department of Defense. SA was intended to prevent military adversaries from using the highly exact GPS signals. The government turned off SA in May 2000, which significantly bettered the accuracy of civilian GPS receivers. |
If you tinker with Garmin GPS devices, you in all probability want it.
GPS User Manual: Working with Garmin Receivers
