An electronic system and an algorithm for estimating pedestrian geographic location in urban terrain is reported in the paper. Different sources of kinematic and positioning data are acquired (i.e.: accelerometer, gyroscope, GPS receiver, raster maps of terrain) and jointly processed by a Monte-Carlo simulation algorithm based on the particle filtering scheme. These data are processed and fused to estimate the most probable geographical location of the user. A prototype system was designed, built and tested with a view to aiding blind pedestrians. It was shown in the conducted field trials that the method yields superior results to sole GPS readouts. Moreover, the estimated location of the user can be effectively sustained when GPS fixes are not available (e.g. tunnels).

The article presents a comprehensive study of a visual-inertial simultaneous localization and mapping (SLAM) algorithm designed for aerial vehicles. The goal of the research is to propose an improvement to the particle filter SLAM system that allows for more accurate and robust navigation of unknown environments. The authors introduce a modification that utilizes a homography matrix decomposition calculated from the camera frame-to-frame relationships. This procedure aims to refine the particle filter proposal distribution of the estimated robot state. In addition, the authors implement a mechanism of calculating a homography matrix from robot displacement, which is utilized to eliminate outliers in the frame-to-frame feature detection procedure. The algorithm is evaluated using simulation and real-world datasets, and the results show that the proposed improvements make the algorithm more accurate and robust. Specifically, the use of homography matrix decomposition allows the algorithm to be more efficient, with a smaller number of particles, without sacrificing accuracy. Furthermore, the incorporation of robot displacement information helps improve the accuracy of the feature detection procedure, leading to more reliable and consistent results. The article concludes with a discussion of the implemented and tested SLAM solution, highlighting its strengths and limitations. Overall, the proposed algorithm is a promising approach for achieving accurate and robust autonomous navigation of unknown environments.