Abstract: A method and apparatus which perform efficient projection of 4-dimensional data (3 spatial and 1 time dimension) onto planar grids are described. Multiple frames of data are drawn from a limited time history data buffer and projected onto a planar grid, which need not be flat, defined in its own coordinate system. Higher dimensional data structures can also be formed from multiple projection grids. Measurement data from multiple data frames is projected into the planar grid such that distance out of plane is the z-dimension. Computational efficiency is achieved by processing only those data samples that are relevant to the planar grid. To be considered relevant, the impulse response of the sensor's measurement rays must cross the planar grid. Samples of relevant rays must also map onto the planar grid's coordinate mesh to be relevant. Multiple data measurements may determine the planar grid's final amplitude result.

Abstract: A method and apparatus for automatically controlling the tilt of a radar antenna to avoid ground clutter returns while scanning the weather formations of most interest. In one embodiment a terrain database is utilized to determine tilt angles for different terrain cells. The tilt angle is determined starting at the aircraft position and working out to the radar range. If a tilt angle for a more distant cell is less than for a nearer cell it is ignored taking shadowing into account. In another embodiment the weighted tilt angle frequencies are entered into a histogram and the histogram is scanned to obtain a tilt angle resulting in an acceptable amount of ground clutter.

Abstract: A radar gathers terrain data which is compared to a stored terrain data base using a test statistic. The test statistic can be used to validate the terrain data base information and/or the aircraft position data.

Abstract: A classifier employing general frame wavelets for improving target recognition while decreasing computational intensity is disclosed. A wavelet selection means compares a portion of a time dependent input signal from a receiver with a set of sample wavelets, each wavelet being bandpass limited, locally supported, and mean zero, and selects a prototype wavelet resembling the input portion. A resolving means expands the prototype wavelet onto a basis of wavelet functions having variations in scale and delay, and resolves the input signal onto the basis of functions. A regionpass filter identifies a region from a grid of resolved coefficients that contains features of a target from the input signal and discards coefficients outside the region. A separability filter passes select coefficients from a scale band within the identified region where separability among known targets is high. A comparator compares the selected coefficients with an exemplar of known targets to indicate a recognition of the target.