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AUTONOMOUS RANGE-ONLY TERRAIN AIDED NAVIGATION

  • US 20160047657A1
  • Filed: 03/25/2013
  • Published: 02/18/2016
  • Est. Priority Date: 03/25/2013
  • Status: Active Grant
First Claim
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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; and

    during 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.

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