Over 30 navigation satellites are zipping around high above Earth. These satellites can tell us exactly where we are. Satellites act like the stars in constellations—we know where they are supposed to be at any given time.
A receiver, like you might find in your phone or in your parents car, is constantly listening for a signal from these satellites. The receiver figures out how far away they are from some of them. Once the receiver calculates its distance from four or more satellites, it knows exactly where you are.
From miles up in space your location on the ground can be determined with incredible precision! They can usually determine where you are within a few yards of your actual location. More high-tech receivers, though, can figure out where you are to within a few inches! The ancient sailors of history would be flabbergasted by the speed and ease of pinpointing your location today.
The U. Each of these 3, to 4,pound solar-powered satellites circles the globe at about 12, miles 19, km , making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky.
This operation is based on a simple mathematical principle called trilateration. Trilateration in three-dimensional space can be a little tricky, so we'll start with an explanation of simple two-dimensional trilateration. You find a friendly local and ask, "Where am I? This is a nice, hard fact, but it is not particularly useful by itself. You could be anywhere on a circle around Boise that has a radius of miles, like this:.
You ask somebody else where you are, and she says, "You are miles from Minneapolis, Minnesota. If you combine this information with the Boise information, you have two circles that intersect. You now know that you must be at one of these two intersection points, if you are miles from Boise and miles from Minneapolis. If a third person tells you that you are miles from Tucson, Arizona, you can eliminate one of the possibilities, because the third circle will only intersect with one of these points.
You now know exactly where you are -- Denver, Colorado. This same concept works in three-dimensional space, as well, but you're dealing with spheres instead of circles. In the next section, we'll look at this type of trilateration. Fundamentally, three-dimensional trilateration isn't much different from two-dimensional trilateration, but it's a little trickier to visualize. Imagine the radii from the previous examples going off in all directions.
So instead of a series of circles, you get a series of spheres. If you know you are 10 miles from satellite A in the sky, you could be anywhere on the surface of a huge, imaginary sphere with a mile radius. If you also know you are 15 miles from satellite B, you can overlap the first sphere with another, larger sphere. The spheres intersect in a perfect circle. If you know the distance to a third satellite, you get a third sphere, which intersects with this circle at two points. The Earth itself can act as a fourth sphere -- only one of the two possible points will actually be on the surface of the planet, so you can eliminate the one in space.
Receivers generally look to four or more satellites, however, to improve accuracy and provide precise altitude information. 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. Countries continue to build and make improvements to their GPS systems. 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. Geotab's blog posts are intended to provide information and encourage discussion on topics of interest to the telematics community at large. Geotab is not providing technical, professional or legal advice through these blog posts.
While every effort has been made to ensure the information in this blog post is timely and accurate, errors and omissions may occur, and the information presented here may become out-of-date with the passage of time.
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Read about the past, present, and future of the Geotab GO device. Learn all about the Geotab Drive app for Hours of Service, electronic logging and vehicle inspection. Skip to main content. 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. Construction, mining and off-road trucking: From locating equipment, to measuring and improving asset allocation, GPS enables companies to increase return on their assets.
Check out our posts on construction vehicle tracking and off-road equipment tracking. Transportation: Logistics companies implement telematics systems to improve driver productivity and safety.
A truck tracker can be used to support route optimization, fuel efficiency, driver safety and compliance. How accurate is GPS?
Some factors that can hinder GPS accuracy include: Physical obstructions: Arrival time measurements can be skewed by large masses like mountains, buildings, trees and more. Atmospheric effects: Ionospheric delays, heavy storm cover and solar storms can all affect GPS devices. Ephemeris: The orbital model within a satellite could be incorrect or out-of-date, although this is becoming increasingly rare.
Numerical miscalculations: This might be a factor when the device hardware is not designed to specifications.
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