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How does a GPS tracking system work?

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velappan
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re: How does a GPS tracking system work?
velappan   10/29/2010 5:37:05 AM
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i have knowledge in GPS and how to comments used in pic micro controller... plz help me..

Jagdish Bisawa
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re: How does a GPS tracking system work?
Jagdish Bisawa   10/29/2010 7:20:38 AM
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Velappan, With an incomplete, improperly famed question, nobody will be able to help you. Please frame your questions in a correct manner & maintain the content-sanctity of the site.

Panch
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re: How does a GPS tracking system work?
Panch   10/29/2010 12:03:54 PM
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Can you comment on how GPS and a map (e.g. Google map) can interact? If I give the destination location, how is it able to map the best possible route and track if I am going on the right track? Another related question I have is that for the active system, does it mean that the receiver sends a feedback signal back to the satellites? If so, how does it work? If not, what is the path taken for the reverse data tx?

Jagdish Bisawa
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re: How does a GPS tracking system work?
Jagdish Bisawa   10/29/2010 1:02:56 PM
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The GPS Map integration is not a simple affair & is probably out of the scope of this article. Normally, the Map software is integrated with another software that is reading the GPS co-ordinates, using the API of the Map software. How it can find the optimum path depends on the path-tracking algorithm that is used. You have misunderstood the definition of Active GPS. Active GPS does not reply back to the satellite ( it is still a one-way communication). However, Active GPS enables the transmission of the position information, using available network to a (usually) central server. The central server thus enables monitoring of the GPS co-ordinates in real-time, thereby leading to application like Vehicle Tracking System or human-tracking.This is in contrast to the Passive GPS systems that the author is talking about. Passive GPS sytems store the data in their memory devices, to be read-out by the user or to be transmitted at fixed transmission points along the journey

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.

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.

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 ?

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).

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.

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......

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