Trilateration in Android using iBeacons

Question

We want to implement some kind of indoor position determination using iBeacons. This article seems really interesting, in which the author implemented the Non-linear Least Squares Triangulation, using the Eigen C++ library and the Levenberg Marquardt algorithm. Since Eigen is written in C++, I tried to use JNI and Android NDK in order to use it but it throws a lot of errors that I have no idea how to solve and I couldn´t find anything online. I also tried to use Jeigen, but it does not have all the functions that we need.

So, my questions are:

1. Has someone ever implemented some kind of Trilateration using beacons in Android?

2. Do you think that using Eigen+JNI+NDK is a good solution? If yes, have you ever implemented Levenberg Marquardt using that combination?

3. Are there better options than the Levenberg Marquardt algorithm for calculating the trilateration in a Android application?

Barstow

Did you try altbeacon.github.io/android-beacon-library/download.html ? – Devi

I gave an example of how to implement some Eigen funtions with Java here. – Audun

Answer 1

Take a look at this library: https://github.com/lemmingapex/Trilateration

uses Levenberg-Marquardt algorithm from Apache Commons Math.

For example.. into the TrilaterationTest.java

you can see:

double[][] positions = new double[][] { { 1.0, 1.0 }, { 2.0, 1.0 } };
double[] distances = new double[] { 0.0, 1.0 };

TrilaterationFunction trilaterationFunction = new TrilaterationFunction(positions, distances);
NonLinearLeastSquaresSolver solver = new NonLinearLeastSquaresSolver(trilaterationFunction, new LevenbergMarquardtOptimizer());

double[] expectedPosition = new double[] { 1.0, 1.0 };
Optimum optimum = solver.solve();
testResults(expectedPosition, 0.0001, optimum);

but if you see the objectivec example https://github.com/RGADigital/indoor_navigation_iBeacons/blob/show-work/ios/Group5iBeacons/Debug/Managers/Location/NonLinear/NonLinear.mm you can note that the accuracy is used as an assessment parameter and not the distance.

Trilbee

Works great! When using the trilateration algorithm, make sure to convert (lat, long, alt) into Cartesian coordinates (x, y, z) as required by the library. – Compressor