The ground dimensions corresponding to the pixel count are calculated based on the direction of the scan line and the scan angle, thus locating the target with respect to the CFOV. Next, the position of the CFOV is computed with respect to a previous set of nadir coordinates (aircraft latitude and longitude) using the aircraft yaw, pitch and roll angles, its altitude, and the gimbal angle measurements. Combining the two ground dimensions, target to CFOV and CFOV to nadir, completely defines the target location. The necessity of this intermediate step is discussed in the paper. The converse problem of pointing to a target of known coordinates, given the present aircraft location, is also addressed. The pointing algorithm uses the same equations derived for target location, but almost in reverse order. Finally, an error analysis is also provided to assess the accuracy of the target location technique. |
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