+Relative positioning methods however only yield a position relative to a
+defined point, and mostly can be applied with cheap hardware. The best-known
+approach in this field is \definition{dead reckoning}, which computes the
+position relative to an initial starting point by considering the covered
+distance and course the robot has moved. In the case of mobile robots, the
+covered distance can be simply computed in real time from the revolution of its
+wheels, or by accelerometers the robot may be equipped with.
+
+The advantage of dead reckoning is that it is easy and fast to implement.
+However, there is also a drawback. The vehicle's current position is based on
+its previous position, and distance and course measurement is mostly imprecise.
+the error of the calculated position grows with time. In order to maintain a
+certain accuracy, countermeasures need to be taken to keep the error as small as
+possible.
+
+In this thesis, the popular Roomba manufactured by the iRobot Corporation is
+used as an instance for an mobile robot, since it is cheap, small, and can be
+simply controlled over a serial interface. The Roomba is accompanied with a
+netbook sitting on top of it, on which runs an application to represent the
+autonomous aspect. This application in turn uses the Wiselib library to control
+the Roomba.
+
+In the first experiment, the Roomba's movement behaviour will be analyzed. Then,
+two different easy approaches for minimizing the positioning error are presented
+and tested for their suitability.
+
+\chapter{Related Work}
+There are already some results on the problem. Yamauchi proposes to use dead
+reckoning with evidence grids to represent the robot's view of the
+world.~\cite{yamauchi} Evidence grids are subdivisions of the Cartesian space
+into cells, and each cell is assigned a probability value representing the
+estimated probability of occupancy by the robot. The robot now explores its
+environment, using its sensors to detect moving and fixed obstacles, and finally
+tries to find its home location again using dead reckoning. On its way back, it
+creates a second evidence grid. Finally, both grids are incorporated by an
+algorithm, which estimates the error in orientation and translation.
+Experimental results with a real robot showed a maximum translation error of 28\%
+and an orientation error of 25\%.
+
+Chong and Kleeman use high-precision odometry to increase the accuracy
+of position estimation by dead reckoning.~\cite{chongkleeman} They succeeded in
+building a odometry system that is as good as the best reported system, but can
+be fabricated at low-cost.
+
+Borenstein and Feng design a benchmark for mobile robots.~\cite{umbmark} They
+show how to measure systematic and non-systematic errors, and how to correct
+them.