AUTONOMOUS RANGE-ONLY TERRAIN AIDED NAVIGATION

摘要

AROTAN provides for autonomous terrain aided navigation that is fully independent of the position uncertainty of the vehicle during flight. AROTAN aligns a grid to the search space and periodically updates the search space during the measurement history to account for growth in position uncertainty. AROTAN computes terrain sufficiency statistics for a moving history to provide robust criteria for when to perform the correlation. A post-correlation refinement provides an additional correction of the horizontal position error and a correction of the altitude. AROTAN can quickly provide the vehicle's location based on the correlation from a single measurement history.

主权项

1. A method for autonomous terrain aided navigation of an airborne vehicle, comprising the steps of:
a) loading a terrain height database comprising heights of terrain at given locations from a terrain reference onto the vehicle, said database formatted independently of a flight path of the airborne vehicle over the terrain; b) initializing a two-dimensional search space about a horizontal position estimate of the airborne vehicle based on an uncertainty of the horizontal position estimate; andduring flight of the airborne vehicle,
c) gathering a history of range-only measurements from the vehicle to the terrain and for each range measurement calculating range predictions from an updated altitude estimate and from terrain heights in the database for positions of the vehicle on an indexed grid aligned to the search space about an updated horizontal position estimate, and updating said search space based on the uncertainty of the updated horizontal position estimate; d) performing a correlation between the history of range-only measurements and the range predictions to determine a correlation offset on the grid, the orientation of the grid and spacing of the grid indices being fixed over the history for each said correlation; e) using the correlation offset to generate a position estimate correction to correct the horizontal position estimate of the vehicle and to correct its uncertainty; and f) repeating steps c-e as the vehicle flies over the terrain.