Efforts worldwide are being made to increase accuracyand improve reliability and GPS capabilities. The future of GPS tracking will likely be far more accurate and effective for both personal and business use. Debunking the top 10 vehicle tracking myths.
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What are the three elements of GPS? The three segments of GPS are: Space Satellites — The satellites circling the Earth, transmitting signals to users on geographical position and time of day. Ground control — The Control Segment is made up of Earth-based monitor stations, master control stations and ground antenna. Control activities include tracking and operating the satellites in space and monitoring transmissions. There are monitoring stations on almost every continent in the world, including North and South America, Africa, Europe, Asia and Australia.
User equipment — GPS receivers and transmitters including items like watches, smartphones and telematic devices. How does GPS technology work? Here is an illustration of satellite ranging: As a device moves, the radius distance to the satellite changes. What are the uses of GPS? Navigation — Getting from one location to another. Tracking — Monitoring object or personal movement. Mapping — Creating maps of the world. Timing — Making it possible to take precise time measurements.
Some specific examples of GPS use cases include: Emergency Response: During an emergency or natural disaster , first responders use GPS for mapping, following and predicting weather, and keeping track of emergency personnel. Read more about GPS tracking for first responders.
Health and fitness: Smartwatches and wearable technology can track fitness activity such as running distance and benchmark it against a similar demographic. The GPS receiver figures both of these things out by analyzing high-frequency, low-power radio signals from the GPS satellites.
Better units have multiple receivers, so they can pick up signals from several satellites simultaneously. Radio waves are electromagnetic energy, which means they travel at the speed of light about , miles per second, , km per second in a vacuum. The receiver can figure out how far the signal has traveled by timing how long it took the signal to arrive.
In the next section, we'll see how the receiver and satellite work together to make this measurement. On the previous page, we saw that a GPS receiver calculates the distance to GPS satellites by timing a signal's journey from satellite to receiver.
As it turns out, this is a fairly elaborate process. At a particular time let's say midnight , the satellite begins transmitting a long, digital pattern called a pseudo-random code. The receiver begins running the same digital pattern also exactly at midnight. When the satellite's signal reaches the receiver, its transmission of the pattern will lag a bit behind the receiver's playing of the pattern.
The length of the delay is equal to the signal's travel time. The receiver multiplies this time by the speed of light to determine how far the signal traveled.
Assuming the signal traveled in a straight line, this is the distance from receiver to satellite. In order to make this measurement, the receiver and satellite both need clocks that can be synchronized down to the nanosecond. To make a satellite positioning system using only synchronized clocks, you would need to have atomic clocks not only on all the satellites, but also in the receiver itself. The Global Positioning System has a clever, effective solution to this problem. Every satellite contains an expensive atomic clock, but the receiver itself uses an ordinary quartz clock , which it constantly resets.
In a nutshell, the receiver looks at incoming signals from four or more satellites and gauges its own inaccuracy. In other words, there is only one value for the "current time" that the receiver can use. The correct time value will cause all of the signals that the receiver is receiving to align at a single point in space. That time value is the time value held by the atomic clocks in all of the satellites. So the receiver sets its clock to that time value, and it then has the same time value that all the atomic clocks in all of the satellites have.
The GPS receiver gets atomic clock accuracy "for free. When you measure the distance to four located satellites, you can draw four spheres that all intersect at one point. Three spheres will intersect even if your numbers are way off, but four spheres will not intersect at one point if you've measured incorrectly. If it hasn't, put the GPS outside with a clear view of the sky and have a cup of tea. If you have a GPS in a vehicle, it's better to wait for the unit to get a fix before driving off.
Receiving ephemeris data for a satellite takes 30 seconds. If you momentarily interrupt the signal during that time the GPS it could take up to a minute more to get the ephemeris for that satellite as it has to start over. If you drive in an area with tall buildings or other obstructions it may take a long time to get the ephemeris data, for four satellites, that is needed for the first fix.
The accuracy of the position your GPS reports is influenced by a number of factors, such as the positions of the satellites in the sky, atmospheric effects, satellite clock errors and ephemeris errors etc. GPS units often show on the screen an accuracy figure, e. EPE on Garmin units. Under ideal conditions, this may be 5, or even 3 metres. Manufacturers are vague on exactly how this figure is determined and it would be unwise to take this figure literally.
You'll get a more realistic figure by looking in the specification section of your GPS receiver's user-manual. The error in altitude will probably be at least twice the horizontal error.
WAAS uses a network of ground-based reference stations. Readings from the reference stations are used to correct for some of the sources of error mentioned above. The data from ground reference stations is transmitted to the GPS using longwave radio, FM radio, or even cellphones. You need 3 GPS satellites for a 2D fix i.
Typically a GPS will track many more satellites than. We know where they are because they constantly send out signals. A GPS receiver in your phone listens for these signals. Once the receiver calculates its distance from four or more GPS satellites, it can figure out where you are. Earth is surrounded by navigation satellites. Credit: NOAA. GPS can be used to keep an eye on dangerous natural hazards, too!
Tsunamis GPS can help provide early warning of tsunamis.
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