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How does a GPS tracking system work?

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Ndukuru
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re: How does a GPS tracking system work?
Ndukuru   11/2/2012 2:09:01 PM
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Thanks for your article.I am currently looking for a means of tracking items that are about 13,000ft subsea and at pressures of 10,000psi max and 400degF max.How can GPS tracking be applied to such conditions?

BillsBlots
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re: How does a GPS tracking system work?
BillsBlots   11/5/2010 1:54:58 PM
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Aleks, the timing and synchronization are a bit complicated for the scale of this well-scoped article, but the issues you raised have ingenious solutions. The fact that a typical family now may have 3,4, or 5 GPS enabled devices at an ever cheapening price is a testament to Economies of Scale and a free market economy. The GPS capability, formerly requiring a stand alone box for all the receiver circuitry, is now mass produced on a chip that may be embedded in most anything, and which includes a sophisticated satellite receiver and communications interfaces, requiring only connection to an antenna to receive the radio signals from the satellites. The laws of physics that determine radio energy path loss from satellite to ground have not changed, but are increasingly overcome by efficient circuits, more transmit power at the satellite, and phenomenally stable and sensitive receivers on earth, allowing us to "get away with" smaller and smaller antennas on earth to maintain the same radio path budget. It is remarkable both technically and to be so affordable, now considered mundane and to be an expected feature of everything from phones to automobiles, even for security of a mechanic's tool box which may be equipped with a GPS and cell phone that automatically dials for help and gives its location when it believes it is being stolen.

Aleksandartomic
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re: How does a GPS tracking system work?
Aleksandartomic   11/5/2010 12:50:27 PM
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There are many articles about how GPS works. Usually there are not targeting core of the explanation of the GPS system… Triangulation is simple to understand but never saw article to explain simple principle so I can say … Yes! I understand now… waoo! Just to mention triangulation term is not enough to explain GPS. But we can get sense that we understand something about GPS by using words triangulation. Triangulation, but where is simple explanation about tightly synchronization between satellites, delays between channels inside receiver. Something about signal sent from satellite, or how is signal coded, how GPS receiver which cost £40 is capable to receive so many channels to decode them to calculate accurate delays between channel and at same time to process data (which in turn produce delays). It must be some very creative ideas behind that. There are a fantastic and exciting ingenious solutions how all this is solved, really exciting and is not necessary to be complex explanation at all but core of the explanation of the GPS system has been always avoided to be explained on nice popular way to the wider public...

cbonilla
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re: How does a GPS tracking system work?
cbonilla   11/1/2010 2:44:01 PM
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the more satellites your receiver can see the more accurate the positioning. Think about it, you are triangulating, therefore, the more perspectives you have the better the outcome.

David Ashton
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re: How does a GPS tracking system work?
David Ashton   10/31/2010 10:34:43 PM
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Great article. Would it be too much to ask that we come up with a universal standard of how to transmit GPS location automatically from phones equipped with it whenever a 000 / 112 call is made? It would (a) help emergency services and (b) help trace nuisance callers. With the intelligence in phones these days it should not be difficult. The hard part is getting mankind to agree on a standard for it without too much bickering......

David Ashton
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re: How does a GPS tracking system work?
David Ashton   10/31/2010 10:30:11 PM
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Most of the answers to your questions are within the article: "The Global Positioning System is mainly funded and controlled by the U.S Department of Defense (DOD)" "The Space Segment of the Global Positioning System consists of 27 Earth-orbiting GPS satellites. There are 24 operational and 3 extra (in case one fails) satellites.." As we are working in a 3-d environment, 3 satellites will give you a 2-dimensional location on the earth's surface, and 4 satellites will give you a 3-dimentional location (ie position plus height). I never was much good at 3-d trig but I can see how this works. Think of disks from each satellite (like saturn's rings) intersecting at your position on the earth's surface. 2 satellites will give you a line where you might be, 3 will give you a point and 4 will give you height as well.

phoenixdave
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re: How does a GPS tracking system work?
phoenixdave   10/31/2010 8:25:16 PM
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@yalanand: I believe there are are currently a minimum of three satellites required for the current GPS systems in order to triangulate the coordinates of the target (the users).

yalanand
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re: How does a GPS tracking system work?
yalanand   10/31/2010 1:48:28 PM
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Thanks for the article. But why do we need 3 satellites ? Who owns these satellites ? And how many satellites are there which are used for GPS currently ?

BillsBlots
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re: How does a GPS tracking system work?
BillsBlots   10/29/2010 2:15:25 PM
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Panch, our GPS system (more appropriately called "Automatic Vehicle Location", or AVL) can turn on a feature enabling the export of the GPS information in a .kml file to Google maps at specified intervals, typically every 1 to 5 minutes. The vehicle icons, speed, direction and identification information of our fleet are overlayed on Google satellite maps, pretty darn cool. All AVL systems overlay that same basic vehicle information on a map system installed on the user's computer, or more typically, the data is collected at a service provider web site to which managers are given login permission and can view location depicted on the host service's map.

Larry M
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re: How does a GPS tracking system work?
Larry M   10/29/2010 1:47:51 PM
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Panch, This is a classical Computer Science problem. All roads are represented as a giant graph with intersections as nodes and distances associated with each branch (road) connecting two nodes. Using Depth First Search or Breadth First Search, all paths are tested, abandoning each path as soon as its accumulated length exceeds any previously generated path. If the user specifies, preference can be given to branches designated as e.g., Interstate highways. If the device senses that you have deviated from the given path, it simply generates a new route from the current location to the given destination.

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