Method of and apparatus for guiding agricultural aircraft

A process for guiding an aircraft responsive to radar signal, said process comprising the steps of:

• a. storing an arbitrary and preselected aircraft flight pattern in said aircraft, each of said flight patterns being stored on an individually replaceable memory means;
• b. continuously receiving radar signals and responsive thereto detecting distances between said aircraft and two ends of a base line defined by two transponders, each transponder having an antenna whereby said aircraft flies at some height above said antenna;
• c. rejecting distances detected in step b. which are inconsistant with previously detected distances;
• d. continuously and automatically displaying an aircraft course jointly responsive to the flight pattern stored in step a. and the radar signals received in step b.;
• and
• e. following said aircraft flight pattern across an area on the surface of the earth which is removed from said base line by a distance which is at least ten times the difference between the altitude of said aircraft and the height of said antennas.

A system for improving the accuracy of radar readings, especially readings used for vehicular guidance, said system comprising a plurality of stations each of which is identified by a pulse repetition rate which is unique to that particular station, means for transmitting station identification cyclically recurring radar pulses, more than one of said plurality of stations receiving said radar pulses intended only for the station which is identified by the predetermined repetition rate of said transmitted radar pulses, means having a variable cyclically recurring acceptance window width for receiving within a single window both at least a selected one of said cyclically recurring radar pulses at said identification rate and any spurious radar frequency pulses which may occur during said window and which recur at a rate which is randomly different from said cyclically recurring rate, said pulses occurring during said window having substantially any suitable energy content relative to each other, means for progressively narrowing the width of said acceptance window centered upon a pulse which continuously appears in the acceptance window at the recurring repetition rate which identifies a desired station, and means for widening said acceptance window if pulses do not reappear during said acceptance window, whereby said window becomes progressively more narrow as it centers and collapses upon a validly recurring radar pulse at the desired station identification rate regardless of the relative energy content of the various signals.

A process using radar signals for guiding vehicles which move at relatively high speed, the speeds being great enough to cause inaccuracy responsive to the movement of said vehicle between the time when a radar interrogation pulse is sent and the time when the reply pulse is received, said process comprising the steps of:

• a. acquiring on board said vehicle ranging and distance data from a plurality of geographically separated and stationary transponder stations responsive to an exchange of interrogation and reply pulses, whereby inaccuracy may result from the distance traveled by the vehicle during said exchange;
• b. deriving data relative to the distance which the vehicle travels during said exchange and the acquisitions of the data readings from the individual tranponder stations;
• and
• c. adjusting the data received in step a. by the data derived during step b. to correlate the different positions of said vehicle during said exchange, whereby the readings derived from said two pulses become as if they were taken relative to the same geographical point.