s As the name suggests, the trilateration technique uses three RTT values to estimate the coordinates of target node. In the trilateration technique, when several landmarks ping the specified target, the three landmarks with smallest RTT values (probably nearest located landmarks) are selected.The algorithm then tries to estimate the location on the basis of overlapping region of the drawn circles around these selected landmarks. Figure 1 depicts this technique. In the trilateration technique, the center of the overlapping region is considered as the location of the target node.
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There are many ways to implement the trilateration technique such as, discussed in the paper Time Of Arrival (TOA)- based trilateration method. These include:
- Linear Least Square Method
- Nonlinear Least Square Method
- Circles intersection with Clustering
- Trilateration in 2D and 3D
Previously we were implementing Linear Least Square Method to implement trilateration. With this method 50% of targets showed distance error above 1000 km. We went through a paper on ?Time Of Arrival (TOA)- based trilateration method which discusses the different positioning algorithms. In this paper that paper it is mentioned that Linear Least Square Method is not very accurate and it just provides initial position which can be used in other positioning algorithms (i.e. Nonlinear Least Squares and Independent Time GPS Least Squares) as initialization value for further iterations.
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