US 12,259,467 B2
Terrain referenced navigation system
Andrew Price, Plympton (GB); and Geoffrey Henderson, Yelverton (GB)
Assigned to ATLANTIC INERTIAL SYSTEMS LIMITED, Plymouth (GB)
Filed by Atlantic Inertial Systems Limited, Plymouth (GB)
Filed on Oct. 21, 2021, as Appl. No. 17/506,903.
Claims priority of application No. 20275164 (EP), filed on Oct. 23, 2020.
Prior Publication US 2022/0128686 A1, Apr. 28, 2022
Int. Cl. G01S 13/931 (2020.01); G01S 19/47 (2010.01); G01S 19/51 (2010.01)
CPC G01S 13/931 (2013.01) [G01S 19/47 (2013.01); G01S 19/51 (2013.01); G01S 2013/932 (2020.01)] 13 Claims
OG exemplary drawing
 
1. A terrain referenced navigation system for a vehicle, comprising:
at least one sensor arranged to measure the elevation of terrain below a current position of the navigation system;
a terrain elevation map comprising a plurality of map posts that each comprise terrain elevation data comprising terrain elevation values;
a land-water detection unit arranged to calculate a proportion of land and/or water of at least a portion of the terrain elevation map based on the terrain elevation values of the terrain elevation data of said portion of the terrain elevation map; and
an iterative algorithm unit arranged to determine a position estimate of the navigation system and thus the vehicle and output the position estimate to a further system of the vehicle, wherein in each iteration the iterative algorithm unit is arranged to:
receive the measured terrain elevation data;
receive the proportion of land and/or water of at least a portion of the terrain elevation map from the land-water detection unit;
determine whether the current position estimate of the navigation system is over a land-water transition based on the proportion of land and/or water received from the land-water detection unit; and
update the position estimate for the next iteration based on the current position estimate, the measured terrain elevation data, the stored terrain elevation data and whether the current position estimate of the vehicle is over a land-water transition;
wherein the iterative algorithm unit is arranged to apply a Q-boost to a height state of the iterative algorithm unit when the iterative algorithm unit determines that the navigation system is located above a land-water transition;
wherein the Q-boost applied to the height state is equal to a predetermined amount; and
wherein the predetermined amount is greater than (0.5 m)2, and wherein the position next iteration is based on the Q-boost.