Patent ID: 11959729
Assignee: ATLANTIC INERTIAL SYSTEMS LIMITED
Field: Other special machines (Mechanical engineering)
Classification: CPC F  G  B | IPC F

Claim 5:
6. A terrain-referenced navigation method comprising:
receiving input from a radar altimeter;
matching radar altimeter measurements of terrain already traversed with the stored digital terrain map in order to calculate aircraft position relative to the stored digital terrain map to determine a terrain-referenced aircraft position, the digital terrain map comprising a plurality of map posts of terrain elevation data;
calculating a fall line for a projectile starting from the terrain-referenced aircraft position as a launch point;
directly comparing the fall line with the digital terrain map, by incrementally comparing a height of the projectile along the fall line with a height of the terrain by searching map data in the stored digital terrain map according to a coarse search of the digital terrain map and then according to a fine search of the digital terrain map in order to find an expected impact point on the terrain; and
displaying, to a pilot, the expected impact point on the terrain on an aircraft display;, wherein the coarse search of the digital terrain map comprises:
incrementing along the fall line to a boundary of a map sheet, the map sheet comprising a subset of the map posts in the stored digital terrain map, the subset comprising a plurality of map posts;
calculating a maximum height of terrain in the map sheet; and
comparing the height of the projectile at the map sheet boundary to the maximum height of terrain in the map sheet.