A new approach to improve mobile localisation based on angular deviation measurements in urban areas

In urban areas, localisation systems based on the use of satellites such as GPS, GLONASS or the future EGNOS may not provide a sufficient availability and have to be complemented by other systems. Our study is focused on a localisation of terrestrial mobiles in urban areas using a radiogoniometer approach or direction finding of several broadcasting stations. The errors of these angular measurements are mainly due to the multipath and masking effects of buildings and trees. This paper presents theoretical and experimental results on angular deviation of direction finding obtained in simple street configurations in two frequency bands: 100 and 900 MHz. The theoretical analysis is based on the uniform theory of diffraction and Snell-Descartes reflection laws. Two specific radiogoniometers presenting specific radiation pattern were developed. Direction finding measurements performed with these sensors are compared using those obtained with a Doppler radiogoniometer. Measurements using existing broadcasting stations in urban areas are also presented and a simple solution to improve angular measurements accuracy is suggested.