A geometrical approach for aerial cooperative obstacle mapping using RSSI observations

The effect of an obstacle on signal strength attenuation is the most important reason that affects the performance of distance estimation based on Received Signal Strength Indication (RSSI) observations. Consequently, in this paper, a novel approach for estimation of the location and height of an obstacle between two UAVs using RSSI observations is proposed which would help to better estimate the location of a radio frequency (RF) source. The long-term goal of developing this approach is to improve the localization of an RF source by removing the effect of obstacle(s) on the signal attenuation. This approach is based on path planning of the UAVs to estimate the tip of the obstacle between them. The change in the diffraction loss observations are used to find the Line Of Sight (LOS) positions of the UAVs. These LOS lines, constructed by connecting the UAVs in LOS situation, are the locus of the tip of the obstacle and used in an iterative geometrical approach for estimation of the location of the tip of the obstacle. Due to the uncertainty in determining the LOS position which is created because of the radius of the Fresnel zone, the motion steps of UAVs, and the non-modeled dynamics in signal attenuation, an EKF filter is used to estimate the tip of the obstacle. The approach has been simulated and the results show that the approach provides better accuracy in RF source localization compared to the basic approach which does not consider the obstacles in the localization process.