This method meets the constraints dictated by the instructed values of turning radius and by the instructed values of direction of approach in terms of route or course to be maintained at the obligatory points of passage. It includes, at the obligatory starting and arrival points of passage, in determining the turning paths that meet the instructed turning radius at these points. These turning paths are located, at each of the obligatory points of passage, on a pair of circles that are tangential to the points of passage, according to the instructed direction of approach valid at this point and oriented in this direction. Once these turning paths have been determined, a selection is made, from among them, according to simple rules, of an initial homing turning path and a final capture path that can be connected by a rectilinear linking path to go from the obligatory starting point of passage to the obligatory arrival point of passage while seeking the shortest possible distance of travel. This method is advantageous because it requires only low computation capacity and can be implemented by the flight management systems with which the present generation of aircraft are fitted out. It also provides for the precise and constantly updated pre-setting of the route followed by the aircraft during a mission, taking account of the obligatory points of passage, and hence for precise estimates of the scheduling of the mission and of the quantity of fuel needed for the mission.

A flight plan revision device may include a first component that determines an auxiliary flight plan corresponding to a lateral revision of the current flight plan, at least over a low altitude flight section. A second component automatically determines at least one decision point indicating the last position of the aircraft along the current flight plan where the auxiliary flight plan can still be activated, so as to allow the aircraft to overfly the terrain in complete safety by following the auxiliary flight plan under the same flight conditions as those envisaged for the current flight plan. A third component automatically presents at least the decision point to a pilot of the aircraft. And a fourth actuatable component allows a pilot to activate the auxiliary flight plan, so as to carry out the lateral revision of the current flight plan.

The present invention provides a method and device for automatically determining a capture trajectory of a flight trajectory for an aircraft, as well as a procedure and system for automatic guidance of an aircraft. The flight trajectory includes at least one lateral trajectory furnished at least with a plurality of rectilinear stretches. The capture trajectory is a lateral capture trajectory that allows the aircraft to join up laterally with a particular rectilinear stretch of the lateral trajectory of the flight trajectory. The capture trajectory is defined to allow a minimum capture duration. An automatic navigation mode is engaged as soon as requested by the pilot to, if necessary, capture and follow the planned flight trajectory.

A flight control indicator for an aircraft includes a central unit that determines a change of vertical or lateral trajectory. A display, which may present a first indicator of a next vertical change and a second indicator of a next lateral change, presents the one of the first and second indicators indicating the change of trajectory which is closest from the current position of the aircraft.

A three-dimensional image of a ground surface taken by a stereoscopic camera is converted to a distance image in a stereoscopic processing section. In an altitude calculating section, after peculiar points contained in the distance image are deleted and further the lens distortion is deleted from the distance image, the distance image is transferred to a real space coordinate. Then, an equation approximating to a plane is obtained from data of the distance image and a length of a perpendicular line to the plane is calculated as a ground altitude.