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25 November 1992 Pure-Cartesian formulation for angle-only and angle-plus-range tracking filters
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This paper presents a pure-Cartesian formulation for angle-only and angle-plus-range tracking filters. Every aspect of the filter--from the expression of the sensor measurements to the filter's state vector--is defined in Cartesian frames. The key to the filter is its measurement expression. In conventional angle-only filters, the sensor measurements are expressed in terms of the elevation and bearing to the target--i.e., in a spherical coordinate system. The proposed tracking filter uses a different approach. Each time step, the filter constructs a Cartesian frame, referred to as the target line-of-sight frame, with origin at the sensor and one axis along the instantaneous expected line of sight to the target. The sensor measurements are then transformed into this frame, and the components of this vector, not the original sensor measurements, are used as inputs to the tracking filter. The technique results in a statistically- uncorrelated Cartesian expression of the sensor measurements. The filter is efficient--it does not require trigonometric functions--and it performs equally well for any line-of-sight geometry. Unlike conventional angle-only filters, its performance does not degrade as target elevation approaches +/- 90 degrees.
© (1992) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Roger L. Gray "Pure-Cartesian formulation for angle-only and angle-plus-range tracking filters", Proc. SPIE 1697, Acquisition, Tracking, and Pointing VI, (25 November 1992);

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