Design Article
Comment
przemek
It's in 3D so you don't get lines but rather circles from intersecting spheres. ...
kartikmandal024
How does a GPS tracking system work?
Patrick Bertagna, GTX Corp.
10/26/2010 9:25 AM EDT
Global Positioning System tracking is a method of working out exactly where something is. A GPS tracking system, for example, may be placed in a vehicle, on a cell phone, or on special GPS devices, which can either be a fixed or portable unit. GPS works by providing information on exact location. It can also track the movement of a vehicle or person. So, for example, a GPS tracking system can be used by a company to monitor the route and progress of a delivery truck, and by parents to check on the location of their child, or even to monitor high-valued assets in transit.
A GPS tracking system uses the Global Navigation Satellite System (GNSS) network. This network incorporates a range of satellites that use microwave signals that are transmitted to GPS devices to give information on location, vehicle speed, time and direction. So, a GPS tracking system can potentially give both real-time and historic navigation data on any kind of journey.
GPS provides special satellite signals, which are processed by a receiver. These GPS receivers not only track the exact location but can also compute velocity and time. The positions can even be computed in three-dimensional views with the help of four GPS satellite signals. 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 that move round the Earth each 12 hours and send radio signals from space that are received by the GPS receiver.
The control of the Positioning System consists of different tracking stations that are located across the globe. These monitoring stations help in tracking signals from the GPS satellites that are continuously orbiting the earth. Space vehicles transmit microwave carrier signals. The users of Global Positioning Systems have GPS receivers that convert these satellite signals so that one can estimate the actual position, velocity and time.
The operation of the system is based on a simple mathematical principle called trilateration. Trilateration falls into two categories: 2-D Trilateration and 3-D Trilateration. In order to make the simple mathematical calculation the GPS receiver must know two things. First it must know the location of the place is to be traced by at least three satellites above the place. Second, it must know the distance between the place and each of those Space Vehicles. Units that have multiple receivers that pick up signals from several GPS satellites at a same time. These radio waves are electromagnetic energy that travels at the speed of light.
A GPS tracking system can work in various ways. From a commercial perspective, GPS devices are generally used to record the position of vehicles as they make their journeys. Some systems will store the data within the GPS tracking system itself (known as passive tracking) and some send the information to a centralized database or system via a modem within the GPS system unit on a regular basis (known as active tracking) or 2-Way GPS.
A passive GPS tracking system will monitor location and will store its data on journeys based on certain types of events. So, for example, this kind of GPS system may log data such as where the device has traveled in the past 12 hours. The data stored on this kind of GPS tracking system is usually stored in internal memory or on a memory card, which can then be downloaded to a computer at a later date for analysis. In some cases the data can be sent automatically for wireless download at predetermined points/times or can be requested at specific points during the journey.
An active GPS tracking system is also known as a real-time system as this method automatically sends the information on the GPS system to a central tracking portal or system in real-time as it happens. This kind of system is usually a better option for commercial purposes such as fleet tracking or monitoring of people, such as children or elderly, as it allows a caregiver to know exactly where loved ones are, whether they are on time and whether they are where they are supposed to be during a journey. This is also a useful way of monitoring the behavior of employees as they carry out their work and of streamlining internal processes and procedures for delivery fleets.
Real-time tracking is also particularly useful from a security perspective as it allows vehicle owners to pinpoint the exact location of a vehicle at any given time. And, the GPS tracking system in the vehicle may then be able to help police work out where the vehicle was taken to if it was stolen.
Mobile Phone Tracking
The development of communications technology has long since surpassed the sole ability to access others when they are mobile. Today, mobile communication devices are becoming much more advanced and offer more than the ability to just carry on a conversation. Cell phone GPS tracking is one of those advances.
All cell phones constantly broadcast a radio signal, even when not on a call. The cell phone companies have been able to estimate the location of a cell phone for many years using triangulation information from the towers receiving the signal. However, the introduction of GPS technology into cell phones has meant that cell phone GPS tracking now makes this information a lot more accurate.
With GPS technology now more commonplace in many new smartphones, this means that the location of anyone carrying a GPS enabled smartphone can be accurately tracked at any time. Cell phone GPS tracking can therefore be a useful feature for business owners, parents, friends and co-workers looking to connect with one another. GPS Tracking Apps (www.gpstrackingapps.com) provides a suit of Apps for the iPhone, iPad, Android, Blackberry and latest Samsung operating system bada all of which can be used to track one another on a location-based social networking portal or from phone to phone.
The technology of locating is based on measuring power levels and antenna patterns and uses the concept that a mobile phone always communicates wirelessly with one of the closest base stations, so if you know which base station the phone communicates with, you know that the phone is close to the respective base station.
Advanced systems determine the sector in which the mobile phone resides and roughly estimate also the distance to the base station. Further approximation can be accomplished by interpolating signals between adjacent antenna towers. Qualified services may achieve a precision of down to 50 meters in urban areas where mobile traffic and density of antenna towers (base stations) is sufficiently high. Rural and desolate areas may see miles between base stations and therefore determine locations less precisely.
|
|
|
|
|
velappan
10/29/2010 1:37 AM EDT
i have knowledge in GPS and how to comments used in pic micro controller... plz help me..
Sign in to Reply
Jagdish Bisawa
10/29/2010 3:20 AM EDT
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.
Sign in to Reply
Panch
10/29/2010 8:03 AM EDT
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?
Sign in to Reply
Larry M
10/29/2010 9:47 AM EDT
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.
Sign in to Reply
Jagdish Bisawa
10/29/2010 9:02 AM EDT
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
Sign in to Reply
an800127
1/7/2013 9:58 PM EST
Hi thanks for the detail insight.
Although i have another confusion on its usage.
As being a caregiver after purchasing any ACTIVE micro gps tracker .
what all i need to do so that i can see track my loved for her safety.
bascically what will the receiver/medium for this.
Sign in to Reply
BillsBlots
10/29/2010 10:15 AM EDT
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.
Sign in to Reply
yalanand
10/31/2010 9:48 AM EDT
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 ?
Sign in to Reply
David Ashton
10/31/2010 6:30 PM EDT
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.
Sign in to Reply
przemek
6/19/2013 2:20 PM EDT
It's in 3D so you don't get lines but rather circles from intersecting spheres. Each satellite signal carries the timing information. This allows you to calculate the distance to each satellite, i.e. you know that you are somewhere on a sphere whose radius is equal to that distance.
If you decode distance to two of the satellites, you know that you are somewhere on a circle formed by intersection of the respective spheres centered at those two satellites. If you add another satellite, it will fix your position to an intersection of three circles, and you can eliminate some of the points because they will be too high or too low with respect to the earths's surface.
Also, the inevitable inaccuracy of the solutions is worse for the vertical component, so it requires four or more satellite acquisitions, even though three should theoretically provide a full 3D solution.
Sign in to Reply
phoenixdave
10/31/2010 4:25 PM EDT
@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).
Sign in to Reply
David Ashton
10/31/2010 6:34 PM EDT
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......
Sign in to Reply
cbonilla
11/1/2010 10:44 AM EDT
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.
Sign in to Reply
Aleksandartomic
11/5/2010 8:50 AM EDT
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...
Sign in to Reply
BillsBlots
11/5/2010 9:54 AM EDT
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.
Sign in to Reply
Ndukuru
11/2/2012 10:09 AM EDT
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?
Sign in to Reply
babylon5
5/8/2013 11:43 AM EDT
Ndukuru,
In order to use the GPS system, the receiver mist be able to see the satellites. The signal from the satellite will not penetrate the water to any significant depth.
Sign in to Reply
an800127
1/7/2013 10:00 PM EST
Hi
Thanks for the detail insight.
Although I have another confusion on its usage.
My question is as being a caregiver after purchasing any ACTIVE micro gps tracker .
what all I need to do so that i can see/track my loved for her safety?
bascically what all can be the receiver/medium for gps tracking Transmitter( web, mobile apps, any other device etc...).
Sign in to Reply
MeirG
5/9/2013 5:51 AM EDT
This article left a lot to be explained about the working of the GPS. I strongly advice the reader to ignore what he read here and refer to better explanations, e.g. from Wikipedia (http://en.wikipedia.org/wiki/Global_Positioning_System).
A receiver uses the accurate position of at least FOUR (not three!) satellites and its DISTANCE to each to estimate FOUR values: earth longitude, earth latitude, elevation (or rather distance from the center of the earth) and time (yes, time, to a rather high precision!)
The position and distances to a given satellite determines a sphere on which the receiver must be positioned. The intersection of three such spheres determines the three earth coordinates: longitude, latitude and elevation.
The accurate position of a satellite is repeatedly transmitted to all receivers in sight. So far so good! But how is the distance to a satellite obtained?
The answer is the time-of-arrival of the satellite transmission at the receiver. Each satellite carries an atomic clock. The time is part of the data packet transmitted by the satellite at regular intervals. The distance to a given satellite would have been known if there was an equally accurate clock at the receiver's end synchronized to those in the satellites. This of course is not practical.
Enter the fourth satellite. Now, instead of solving three equations to obtain three coordinates, we solve FOUR equations to obtain FOUR values, the three coordinates and the (very accurate) time.
For a more complete explanation see the Wikipedia reference.
Sign in to Reply
gps application
5/17/2013 10:55 AM EDT
dear sir
The digital signal how are transmitting to gps and then
gps from how are receving the signal to mobile
Sign in to Reply
Raghavendra Tummepalli
5/22/2013 8:46 AM EDT
Sorry friends,
This might be a repitetive question.Can anyone help me how vehicle tracking sytem works??
Sign in to Reply
kartikmandal024
6/4/2013 11:09 AM EDT
Dear
sir
in gps enabled mobile is there any in build gps or it totally controlled by the network
Sign in to Reply