This thesis describes the development of an offline, cooperative, range-based localization algorithm for use in settings where there is limited or no access to a positioning infrastructure. Motivating applications include underground animal tracking and indoor pedestrian localization. It is assumed that each sensor performs dead reckoning to estimate its current position, relative to a starting point. Each measurement adds error, causing the position estimate to drift further from the truth with time. The key idea behind the proposed algorithm is to use opportunistic radio contacts to mitigate this drift, and hence localize with greater accuracy. The proposed algorithm first fuses radio and motion measurements into a compact graph. This graph encodes key positions along sensor trajectories as vertices, and distance measurements as edges. In so doing, localization is cast as the graph realization problem: assigning coordinates to vertices, in such a way that satisfies the observed distance measurements. The graph is first analysed to certify whether it defines a localization problem with a unique solution. Then, several algorithms are used to estimate the vertex coordinates. These vertex coordinates are then used to apply piecewise corrections to each sensor's dead reckoning trajectory to mitigate drift. Finally, if sufficient anchors are available, the corrected trajectories are then projected into a global coordinate frame. The proposed algorithm is evaluated in simulation for the problem of indoor pedestrian tracking, using realistic error models. The results show firstly that 2D and 3D problems become provably more localizable as more anchors are used, and as the experiment duration increases. Secondly, it is shown that widely-used graph realization algorithms cannot be used for localization, as the complexity of these algorithms scales polynomially or greater with graph vertex count. Thirdly, it is shown a novel piecewise drift correction algorithm typically works well compared to a competing approach from the literature, but rare and identifiable graph configurations may cause the method to underperform.

M. Tech. (Department of Information Technology, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Tracking involves information gathering, manipulation and proving information on the location of a set item. Many single or hybrid technologies – Global Positioning System (GPS), Radio Frequency (RF), Bluetooth (BLT) or Wireless Fidelity (WiFi) – have been used to provide tracking information of an asset of interest. The use of hybrid technology in tracking assets has proven to be effective if the selection of the technologies used is done correctly. This study used a hybrid of GPS and Radio Frequency technologies to track assets of interest because of their characteristics for use inside and outside a building. In this study GPS geo-fencing was used and time interval was used to receive data from the technology. Heuristic methodology, which enabled us to divide a room into sections, was used, where testing was done in sections in a room with different types of material, such as bricks, wood or metal, and the RF signal degradation, called attenuation, was measured. A straight-line distance and a sum of distances at 30-minute intervals were calculated to determine how far the asset had travelled from the point of origin to the new position. A distance of less than 10 metres was ignored. Geofencing was used to trigger an event since it indicates that the asset has crossed the permitted boundary. An RF reader was placed at the door to identify when the asset left a building and triggered an event. A model was used for searching for a missing item in a room. The results showed that the system was able to produce two distances, one straight-line distance and the other the approximate sum distance travelled by the asset in 30-minute intervals. The RF model was able to find an asset in a room filled with different materials.

Der Paradigmenwechsel zur Entwicklungsmethodik innerhalb verteilter Kommunikationssysteme schlägt sich auch in der Telematik zum Anwendungspotential und Systemkomplexität nieder. Dies liefert eine neue Auffasung dessen, was den transparenten Datenkanal ausmacht.

Der Paradigmenwechsel zur Entwicklungsmethodik innerhalb verteilter Kommunikationssysteme schlägt sich auch in der Telematik zum Anwendungspotential und Systemkomplexität nieder. Dies liefert eine neue Auffasung dessen, was den transparenten Datenkanal ausmacht.