Validation Volume Reduction with Tracking in Sensor Coordinates

Tracking in sensor coordinates has numerous benefits, because the filter bypasses the burden of nonlinear coordinates transformation, if consistency in the Cartesian space is guaranteed. Taking advantage of recent breakthroughs in coordinate conversion methods related to bistatic r-u-v (range and direction sines u,v), we develop the r-u-v filter to optimize the association gate volume while maintaining Cartesian consistency. The paper focuses on materializing theoretical gains due to r-u-v tracking in a scenario with a glide vehicle subject to aerodynamic drag and gravity in a guided trajectory. Previous r-u-v filters are mixed-coordinate filters because realistic dynamics is difficult to express in r-u-v, but the present work manages to account for drag, gravity and guidance in r-u-v state equations without excessive complexity. Linear measurement model helps reduce gate volume, especially by accentuating the range accuracy of the sensor. In the presence of the "contact lens" phenomenon, gate volume reduction can be furthered by replacing the Gaussian ellipsoid gate which has a lot of empty space with a fuller and better fitted contact-lens-shaped gate region. Comparative simulations show that benefits are dependent on the sampling frequency and can be attributed to the choice of coordinates used by the filter.