Sparse learning approach to the problem of robust estimation of camera locations

In this paper, we propose a new approach-inspired by the recent advances in the theory of sparse learning-to the problem of estimating camera locations when the internal parameters and the orientations of the cameras are known. Our estimator is defined as a Bayesian maximum a posteriori with multivariate Laplace prior on the vector describing the outliers. This leads to an estimator in which the fidelity to the data is measured by the L_¿-norm while the regularization is done by the L₁-norm. Building on the papers [11, 15, 16, 14, 21, 22, 24, 18, 23] for L_¿-norm minimization in multiview geometry and, on the other hand, on the papers [8, 4, 7, 2, 1, 3] for sparse recovery in statistical framework, we propose a two-step procedure which, at the first step, identifies and removes the outliers and, at the second step, estimates the unknown parameters by minimizing the L_¿ cost function. Both steps are fairly fast: the outlier removal is done by solving one linear program (LP), while the final estimation is performed by a sequence of LPs. An important difference compared to many existing algorithms is that for our estimator it is not necessary to specify neither the number nor the proportion of the outliers.