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Looking around I noticed that many people exchange the terms (tringlulation and trilateration) for the same sense. What's, actually, the correct sense of Triangulation and what are the differences from Trilateration?

thx

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A third locating method worth mentioning is multilateration which "should not be confused with trilateration, which uses distances or absolute measurements of time-of-flight from three or more sites, or with triangulation, which uses the measurement of absolute angles. Both of these systems are also commonly used with radio navigation systems; trilateration is the basis of GPS." –  Kirk Kuykendall Nov 29 '11 at 14:14
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2 Answers

It's already explained in the terms:

Triangulation = working with angles
Trilateration = working with distances.

In real world applications you work with both, or combine them. For example GPS Signals are rather trilateration concepts. Speed and time equals a distance which determines your position...

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I need to go deep into difference about them because I need to know which is the technique of lateration. I understand the trilateration but I can't figure out how lateration can fix a point. Any link about this matter? thx –  adev Nov 29 '11 at 10:15
    
Google is your friend :) intranet.nitrkl.ac.in/GroupEmailfiles/DMFNXCPV_4295.pdf –  Styp Nov 29 '11 at 10:20
    
Great! many thanks! –  adev Nov 29 '11 at 10:26
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unfortunatly even there is not well defined the difference.... :( . It seems that are both based on EDM and azimuth establishment but it doesn't explain the really difference.... –  adev Nov 29 '11 at 10:39
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The difference is clearly explained in the document Martin found, but it is not illustrated. As an example of triangulation, imagine a line segment in the plane and two angles given at its ends. Those angles determine rays; their intersection gives the triangulation point. Now, instead of two angles, suppose two distances from the ends of that segment are given. Those distances determine two circles. There are two points where those circles intersect: they are the trilateration points. –  whuber Nov 29 '11 at 17:19
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These two illustations are from the field of surveying but they should still apply.

Triangulation

As Martin has said, in triangulation, you work with angles as illustrated in the following figure. enter image description here The positions of the points of interest are computed based on measured angles and two know points. From those angles, the distances are computed which are in turn used to calculate coordinates for the target points.


Trilateration

enter image description here

In trilateration, you work with distances. From those distances, you compute the angles. Once computed, you can use them in conjunction with the distances to get the position of the target points.

A simpler example would the one at HowStuffWorks. It is quite similar to how GPS works except that this one's in 2D.

Given only one distance, you only know you are within a certain distance from Boise (which could be anywhere in that radius)

enter image description here

Given another distance from Minneapolis, you can now tell that you are at the intersection of two circle. Still gives you two positions though.

enter image description here

A position from a third location (Tucson), would narrow down your location to only one point.

enter image description here

That's pretty much how GPS works except that GPS is in 3D and you're dealing with spheres instead of circles. You'd also end up with two points instead of a single point with the third satellite but you can eliminate the other point as it's not on the surface of the earth as the illustration shows.

enter image description here


If you would look closely, their goal is the same. To get both distance and direction so that you can get the positions of the points you're interested in. Both of these techniques were invented before GPS and electronic measuring devices (EDM).

Before EDMs, triangulation was favored as it was very hard to measure long distances accurately while it was comparatively easy to measure angles. With the advent of electronic distance measurement tools (total stations and their ilk), trilateration also became popular as it was no longer hard to measure distances.

I hope that clarifies things for you.


Disclaimer: Images are from the ICSM site.

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