Tag Info

Hot answers tagged

22

Cell Towers do not cover the globe or remote/rural areas, Global Positioning System does - however in dense urban areas cell triangulation can be better than GPS. http://en.wikipedia.org/wiki/GSM_localization#Network-based Atomic clocks are expensive to make. A GPS receiver works by measuring the relative time delay of signals from a minimum of three, but ...


16

The "accuracy" figure displayed by your GPS receiver will most likely be fairly reliable, but it can also be 'way off'. It isn't "accuracy" that the GPS is displaying - it is the EPE, which is the Estimated Position Error. In other words, it is the probability that the location the GPS is displaying is within the "accuracy" distance from the true location. ...


6

GPS do not fail that badly with tall buildings, I have plenty of running assets in packed cities with perfect tracing. These skyscrapers actually reflect the signal in a convenient way for GPS. Accelerometers do not give positions away and their accuracy is debatable, Detecting the difference between a starting , a running engine and a door that gets slam ...


5

Cell Tower Triangulation SkyHook provide this service: http://www.skyhookwireless.com/location-technology/coverage.php


4

I would suggest this is due to cost. The Mobile Telecommunication Market is very cut throat and every service provider, manufacturer and software providers are generally taking losses on handset sales in preference for Plan based monthly payment plans. Because of this the overhead of upgrading towers and handset design to include the required hardware and ...


3

You can figure out the accuracy for yourself by calculating the RMS (root mean square) error by taking 10-20 readings of x-y coordinates over a known point (such as a survey monument) and applying a formula. THAT will tell you the true accuracy of your device BUT it will only pertain to that specific point in time that the coordiantes were collected. If you ...


3

There is something in use quite like it though. It's called LORAN (LOng RAnge Navigation). It is a terrestrial radio navigation system using low frequency radio transmitters in multiple deployment (multilateration) to determine the location and speed of the receiver. It fell out of favor though when GPS gained widespread adoption. It still lives on as eLORAN ...


2

I agree with @TreyA that you're going to need DGPS to get to sub-meter accuracy. Post-processing sounds like it would work fine for your application, so there is no reason to buy expensive hardware that can handle real-time DGPS. Unfortunately, you will need a GPS logger that records the relevant information (range and satellite IDs). Some info is here: ...


2

In my experience you need at least 5 of them to have a somewhat accurate sample. I see many with 4 who deviate visibly from reality when projected. The value of NSATS is also not enough to determine accuracy, the quality (gain) of the gps signal is as important. (I see many with NSAT=7 but with less than 30dBm signal gain, 1 decibel referenced to 1 ...


2

Very interesting problem. There are many questions here so I'll give my shot at one. There is such a thing as real-time differential GPS. When we did NASA flight tests, we sent an engineer up to our landing site to setup up the GPS station ahead of the airplane. The station was placed at a known accurate location and broadcast corrections to a GPS ...


2

Well, they actually are used for geolocation (mostly for 911 calls and law enforcement/intelligence surveillance): http://news.bbc.co.uk/1/hi/technology/4738219.stm http://www.foxnews.com/story/0,2933,509211,00.html But for the reasons listed in other people's answers, it's really not a replacement for GPS, but more of a hack that the Feds can use when ...


1

Assisted GPS technologies used for E911 do use techniques similar to GPS to determine position. Techniques such as Advanced Forward Link Trilateration and Enhanced Observer Time Difference use the timing of signals from cell towers to calculate more accurate positions than simple signal strength estimates. Accuracy of around 50m to 200m is possible.



Only top voted, non community-wiki answers of a minimum length are eligible