![]() ![]() My question ist now, what this third variance represents and why it gets automatically computed. The third variance (m) gets automatically calculated in the file pf.c, in the function called pf_cluster_stats, right at the bottom of it, with the formula: Example of the matrix, refined for a little bit better overview: While looking at the data inside this matrix during a run in nav2d (2-dimensional problem), I indeed found, that the matrix does not contain values for the covariance of the (presumed) third dimension. As AMCL is probably developed to be used for 2D as well as 3D localization, it offers a 3x3 matrix, which I would assume would only be parially filled with data in a 2D-environment. I have stumbled upon a little mystery (for me, at least) concerning the calculation of the covariance matrix cov.m, more precicely the last of the nine values of it.Īs far as I have understood the covariance matrix in general, its size depends on the dimensionality of the problem if we move in a 2-dimensional space, we have a 2x2 matrix, while in a 3-dimensional space, we have a 3x3 matrix. In that context I have tried to understand how AMCL (used in the localization of nav2d) works. I'm quite new to robotics and ROS and have worked the past several months with nav2d.
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