Triangulate

[JugglingReferee]

Hello. Noobie here.

A friend and I were talking about location services in cell phones. Then we were wondering about the same thing but on a much smaller scale.

Let's say you're in an open area (eg: baseball field or a golfing driving range), as in no concrete/buildings in the way. Is it possible to place three devices somewhere fixed, and then another device moves around, and when asked to do so, like pressing a button residing on said device, it can determine it's location with that triangulation? Would more than 3 fixed devices be required? Can it be done with 2?

What would you use for the fixed devices? They would have to respond to a signal sent out from the moving device, and then then send back the distance between the two.

With 3 of these distances, the math should be such that the moving device's location can be triangulated, correct?

 

[davenn]

3 is the minimum, with only 2 fixed sensors, you end up with 2 places where the detected object could be. More than 3 detectors just improves the accuracy.

what you want can be done, but its going to require some intense timing accuracy and processing
RADAR of course uses only one sensor and again the timing and processing is pretty complex

Dave

 

[KrisBlueNZ]

As Dave says, the problem with measuring distance using radio waves is that they travel extremely quickly, so your receiver would need to measure extremely small timing differences. GPS receivers do this, but there is a lot of high-tech design involved.

Location services for cellphones, as far as I know, do not use triangulation; the network can simply tell which cell site is closest to the phone based on the received signal strength.

Sound travels around six orders of magnitude slower than electromagnetic radiation, so if you could use sound instead of radio waves or light, the timing would be a lot easier!

 

[BobK]

Two sensors could triangulate an object if is it known to be in a given area. The second position Dave mentioned could be out made to be out of the area.

Bob

 

[OLIVE2222]

cellphones also have a Timing Advance information (to handle the echo) that provide a raw information of the distance from the aerials inside a cell. Cellphones also report the levels of the neighbouring cells, handy data to locate them!

Outdoor location can be based on signal strength (RSSI) too, this if less demanding than time handling but algorithms are still to be implemented and it's still a complex job.

Olivier