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US 11,959,729 B2Granted
Projectile ranging with digital map
AssigneeAtlantic Inertial Systems Limited
InventorsNicholas Robert Geoffrey Wilkinson, Martin Richard Godfrey
Life of this patent
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Abstract
A terrain-referenced navigation system for an aircraft comprises: a stored digital terrain map; a position calculation unit arranged to calculate aircraft position relative to the stored digital terrain map to determine a terrain-referenced aircraft position; a fall line calculation unit arranged to calculate a fall line for a projectile starting from the terrain-referenced aircraft position as a launch point; and an impact point calculation unit arranged to directly compare 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 according to the stored digital terrain map in order to find an expected impact point on the terrain.
Claims14
A terrain-referenced navigation system for an aircraft, the system comprising:
- a memory containing a stored digital terrain map comprising a plurality of map posts of terrain elevation;
- a position calculation processing unit that:
- receives input from a radar altimeter;
- and
- matches 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;
- a fall line calculation processing unit that:
- receives the terrain-referenced aircraft position;
- and
- calculates a fall line for a projectile starting from the terrain-referenced aircraft position as a launch point;
- an impact point calculation processing unit that directly compares 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
- an output processing unit comprising an aircraft display that displays, to a pilot, the expected impact point on the terrain;
- wherein, during the coarse search of the digital terrain map, the impact calculation unit:
- increments 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;
- calculates a maximum height of terrain in the map sheet;
- and
- compares a height of the projectile at the map sheet boundary to the maximum height of terrain in the map sheet.
14 more elements
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.
8 more elements
A non-transitory computer-readable medium or computer program product comprising:
- instructions that are executable by a processor to cause a terrain-referenced navigation system to:
- receive input from a radar altimeter;
- match 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 stored digital terrain map comprising a plurality of map posts of terrain elevation data;
- calculate a fall line for a projectile starting from the terrain-referenced aircraft position as a launch point;
- directly compare 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 according to 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
- display, to a pilot, the expected impact point on the terrain on an aircraft display;
- wherein, during the coarse search of the digital terrain map, the instructions cause the terrain-referenced navigation system to:
- increment 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;
- calculate a maximum height of terrain in the map sheet;
- and
- compare the height of the projectile at the map sheet boundary to the maximum height of terrain in the map sheet.
9 more elements
Dependencies are inferred from the claim text.