1 research outputs found
Nonvisible Satellite Estimation Algorithm for Improved UAV Navigation in Mountainous Regions
This paper presents a very simple and computationally
efficient algorithm for the calculation of the occlusion points
of a scene, observed from a given point of view. This algorithm
is used to calculate, in any point of a control volume, the
number of visible satellites and the Dilution Of Precision (DOP).
Knowledge of these information is extremely important to reject
measurements of non-visible satellites and for the reconstruction
of a fictitious Digital Elevation Map (DEM), that envelops all
the regions characterized by a number of visible satellites lower
than a given threshold. This DEM evolves in time according to
the platform motion and satellite dynamics. Because of this time
dependency, the Digital Morphing Map (DMM) has been defined.
When the DMM is available, it can be used by the path planning
algorithm to optimise the platform trajectory in order to avoid
regions where the number of visible satellites is dramatically
reduced, the DOP value is very high and the risk to receive
corrupted measurement is large. In this paper also presents the
concept of a Safety Bubble Obstacle Avoidance (SBOA) system.
This technique takes advantage from the numerical properties
of the covariance matrix defined in the Kalman filtering process.
A space and time safety bubble is defined according to the DOP
value and is used to automatically determine a minimum fly
distance from the surrounding obstacles