/Incremental smoothing and mapping

Incremental smoothing and mapping

Michael Kaess
PhD Thesis, Tech. Report, Georgia Institute of Technology, December, 2008

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Incremental smoothing and mapping (iSAM) is presented, a novel approach to the simultaneous
localization and mapping (SLAM) problem. SLAM is the problem of estimating
an observer’s position from local measurements only, while creating a consistent map of the
environment. The problem is difficult because even very small errors in the local measurements
accumulate over time and lead to large global errors. While SLAM is a key capability
in mobile robotics today, the problem has a long history in land surveying. And the underlying
estimation problem was already solved by Gauss in 1809 [56, 57] for computing the
orbits of asteroids.

iSAM provides an exact and efficient solution to the SLAM estimation problem while also
addressing data association. For the estimation problem, iSAM provides an exact solution
by performing smoothing, which keeps all previous poses as part of the estimation problem,
and therefore avoids linearization errors. iSAM uses methods from sparse linear algebra
to provide an efficient incremental solution. In particular, iSAM deploys a direct equation
solver based on QR matrix factorization of the naturally sparse smoothing information
matrix. Instead of refactoring the matrix whenever new measurements arrive, only the
entries of the factor matrix that actually change are calculated. iSAM is efficient even
for robot trajectories with many loops as it performs periodic variable reordering to avoid
unnecessary fill-in in the factor matrix. For the data association problem, I present state
of the art data association techniques in the context of iSAM and present an efficient
algorithm to obtain the necessary estimation uncertainties in real-time based on the factored
information matrix. I systematically evaluate the components of iSAM as well as the overall
algorithm using various simulated and real-world datasets.

BibTeX Reference
author = {Michael Kaess},
title = {Incremental smoothing and mapping},
year = {2008},
month = {December},
school = {Georgia Institute of Technology},
address = {Pittsburgh, PA},