(2) (Global Positioning System) A satellite-based radio navigation system run by the U.S. Department of Defense, officially known as NAVSTAR GPS (see also GLONASS, Galileo and Beidou). It was designed so that signals from at least four satellites would be on the horizon at all times, which is sufficient for the GPS receiver to compute the current latitude and longitude (map location) and elevation anywhere on earth to within a range of 15 to 70 feet (see latitude).
MEOs in Six Orbits
In six different orbits approximately 12,500 miles above the earth, the system's 24 MEO satellites circle the earth every 12 hours. The satellites constantly transmit their current time based on atomic clocks and current location on two frequencies in the L-band labeled L1 (1575.2 MHz) and L2 (1227.6 MHz). Most receivers pick up L1, while more advanced receivers pick up both signals for greater accuracy by determining and removing ionospheric delays.
There are also numerous government and commercial monitoring networks around the world that use earth-based reference stations to improve accuracy (see GPS augmentation system).
Whether installed in vehicles or carried by hand, a GPS receiver calculates the distance to the satellites by comparing the times the transmitted signals were sent with the times received. By knowing the precise locations of the satellites at a given moment, the receiver uses triangulation, the navigation technique of ship captains for centuries, to pinpoint its own location. See triangulation.
At Least Three Satellites
If four satellites are picked up, map location and elevation can be computed. If three are available, only location can be derived, and if less than three signals are received, the system cannot compute its current location unless it uses the speed of the vehicle (see in-dash navigation).
No More Asking Directions
Widely used in the military, GPS is used in many other applications, including agriculture, oil, gas, mining and construction.
In the mid-1990s, GPS car navigation systems emerged, and by 2000, in-dash systems were either standard or an option in luxury cars. Subsequently, after-market units were made available for all vehicles. Portable units can be taken from car to car, and navigation software can be added to a laptop computer. Small handhelds help hikers and hunters find their way. See vehicle tracking, GPS augmentation system, mobile positioning, GIS glossary, MEO, GNSS and Galileo.
GPS in the Car
In 1996, Sony's NVX-F160 was one of the first navigation systems for the road. It could direct you to the nearest restaurant, hotel or other point of interest. (Image courtesy of Sony Corporation.)
GPS in the Woods
Portable navigation systems work anywhere. The flat object pointing up at the top of this unit is the antenna.
GPS On a Laptop
Delorme's Street Atlas turns any laptop into a "nav," and the software is extremely informative. The bottom clip shows all satellites in range (it just lost #15), their elevation (Elv), azimuth (Az) and signal-to-noise ratio (dB). NET means (N) the satellite is used for navigation, (E) ephemeris data is available, and (T) it is being tracked. The yellow object on the dash is the antenna.
![]() | Reproduced with permission from Computer Desktop Encyclopedia. Copyright (c) 1981-2008 The Computer Language Company Inc. All rights reserved. |
Additional Resources
- TechForward advocates the cause of temporary ownership
- I have been MEANING to write about the Los Angeles-based start-up TechForward for weeks now, but felt like I didn't have enough time to write the truly thoughtful post that it deserved. Now, I'm forcing myself to get off my butt, strangely enough, because I'm having a moral dilemma over...
- Blog posts 2008-07-04
- Trick out your fleet with fuel consumption monitors from Networkcar
- OK, I admit it. When I bought my car a year-and-a-half ago, comparing the fuel consumption metrics among the different models WAS part of the equation, but not the most important part. Now, with gas lines forming in my own little town and people putting summer trips...
- Blog posts 2008-07-03
- What is the best method for picking up an iPhone 3G on July 11th?
- What is the best method for picking up an iPhone 3G on July 11th?Going EarlyI have a pretty decent sized AT&T Wireless store a quick walk down the street from my place. I'm guessing since it isn't in the busier parts of town it won't have a ton of traffic...
- Discussion threads 2008-07-02
- Garmin Nuvi 880
- Ever since the Garmin Nuvi 880 was announced at CES 2008, we've been excited to get out hands on this portable navigation system. Given the good track record of the other Nuvi series devices, we expected more of the same, solid feature list and good performance. However, we were most...
- Product reviews 2008-06-30
- Cell phones tracking nightlife activity
- Cell phones tracking nightlife activityGPS Features we will Hate!!!Sounds great! GPS features are certainly very exciting nd i can see most devices in corporating GPS features in the long run. Whilst location base services obtainde from GPS features can be helpful, there are several downsides to GPS features in our...
- Discussion threads 2008-06-30
- Tele Atlas, Google in map pact
- Tele Atlas, a Netherlands-based digital map provider, said Monday that Google has signed a five year licensing agreement to broaden the search giant's map services. Specifically, Google gets Tele Atlas' content in more than 200 countries. The deal covers Google's "current and future map-based services and navigation...
- Blog posts 2008-06-30
- Cell phones tracking nightlife activity
- A Columbia University computer science professor has co-founded a New York-based company named Sense Networks to sell tracking software to other companies. It is also distributing a free version of this software named Citysense, which shows on your cell phone where the wild things are happening in your own town....
- Blog posts 2008-06-29
- LG Dare (Verizon Wireless)
- One of the most notable fallouts of the Apple iPhone launch last year is the ever growing trend of touch-screen phones. LG was one of the first manufacturers out the gate with phones such as the LG Voyager and the LG Vu dazzling us with features that we couldn't get...
- Product reviews 2008-06-27
- Will the iPhone 3G support MMS?
- Will the iPhone 3G support MMS?Same settings?I don't think that the same settings for MMS apply as for SMS but never mind. The Iphone was a novelty because of its nice touchscreen. It was and it is an incomplete piece of work. No mms while people are using that for...
- Discussion threads 2008-06-27
- Would Microsoft ever split itself up?
- Would Microsoft ever split itself up?they couldThey could, but they'll never do that. Micro$oft is too greedy. In my perfect world I want to see Microsoft as a software company and another branch as a hardware company for actual computers, Phones and other devices, like Music Players, GPS, and Car-Support.The...
- Discussion threads 2008-06-27
- First Symbian Foundation handsets due in 2010
- First Symbian Foundation handsets due in 2010Well if we can believe both dates....Android 4th Quarter 2008 and Symbian in 2010, well Android will have quite a head start to deal with.I wouldnt bank on that.Android is on a closed platform released fairly recently...I've been programming for Symbian in OPL and...
- Discussion threads 2008-06-25
- Samsung Soul SGH-U900 (unlocked)
- Photo gallery:Samsung SoulThe Samsung Soul (aka the SGH-U900) was one of the stars of this year's GSMA World Congress in Barcelona. Samsung showed it off at a big press conference and huge banners with images of the phone covered the city, from the airport baggage claim to the convention center....
- Product reviews 2008-06-24
- Nokia Symbian deal winners and losers
- Nokia Symbian deal winners and losersNokia Symbian - What's in a name?Heads up! It looks like Nokia's product naming consultants did not do their homework for similar names with other mental images and associations. Check out www.sybian.com. Or, how about the Symbionese Liberation Party that kidnapped Patty...
- Discussion threads 2008-06-24
- LG LX400
- LG is typically more known for its consumer-level handsets like the LG Voyager and the LG Chocolate. So it was a pleasant surprise to us when we found out LG was partnering with Sprint to come up with the LG LX400, one of the first phones to support QChat, a...
- Product reviews 2008-06-23
- 2009 Pontiac Vibe GT
- Photo gallery:2009 Pontiac Vibe GTWe found the economy car efficiency, the tight build quality, and the odd body style all appealing on the 2009 Pontiac Vibe GT. But once we started looking at the details, we realized it was a Toyota. The hard flooring in the cargo area and the...
- Product reviews 2008-06-23
- AT&T may pay Apple $325 for each iPhone 3G sold
- AT&T may pay Apple $325 for each iPhone 3G soldIs The IPhone REALLY Worth It?Let's see...I have an AT&T Tilt with Opera Mobile on it...I have a pop-out keyboard that I can type relatively fast on it, or I can opt to use the touch keyboard with the stylus.I can...
- Discussion threads 2008-06-23
- I am Batman
- I am Batmanre: I am BatmanIf I understand this correctly... they'll pay for your Phone usage but not your data, correct? First off, I'd say that's odd in this day and age. Usually I see that companies pay for Both or None.In any case, it sounds like you're...
- Discussion threads 2008-06-23
- Are you a dual mobile phone-carrying superhero dork?
- In various blogosphere responses to my previous piece in which I discussed the poor broadband alternatives and the sad outlook for FIOS in my sleepy New Jersey suburban town, I was accused of being a "whiner" for not "sucking up" the additional costs of having to pay for the overages...
- Blog posts 2008-06-23
- Nokia to take location-based social networking mainstream
- Nokia to take location-based social networking mainstreamI agree with your thoughts on this !Yes social gps as I like to call it is the way of the future and yes Nokia is not the only player in town they should keep there eyes open for this up and coming social...
- Discussion threads 2008-06-23
- ElshayalSmart (zip)
- Current Features View and Edit 2D & 3D shape maps, GPS, add, delete, swap layers, layers properties, zoom in & out, pan, and identify, Selection, Data table, Query builder, Create network, Shortest path, Printing, Save Image, Save map, Save Layer, Move vertex and features, Snap vertex , Table Editing, Map...
- Software downloads 2008-06-23
Neighboring Terms
Premier Vendor Content Whitepapers, webcasts & resources from our Power Center Sponsors
- Marc Canter: The master of multimedia speaks
-
In this Super Techies interview, larger-than-life techie Marc Canter talks with ZDNet's Editor in Chief Dan Farber about his career as a multimedia pioneer.
- Watch the video >>
- New entries posted to Know Issues, Best Practices and Workarounds Wiki
-
Latest Topics: Running virtual machines and DHCP can cause Intel® AMT to be inaccessible; Wildcard certificates are currently not supported for remote; Dell 755 returns a duplicate UUID during activation configuration.
- See the latest entries on the Intel Wiki >>
- Learn how collaboration fuels success with this FREE Economist report
-
According to a new study from the Economist, future success belongs to those who collaborate effectively. Learn how successful collaboration can improve profits, problem-solving, and competitive differentiation.
- Visit Cisco's Collaboration Resource Center today!
- BNET Industries
- Check out BNET's newest resource for managers and executives. Need to do research on your competitors? Don't have time to read every trade pub? BNET Industries is the new source for daily news, insights, and research on 11 major industries and 9,000 public companies.
-
- The technology industry from a different angle
-
- See what's hot in the auto industry
-
- Stay on top of the energy industry





