Reduction of altitude error using forecasted atmospheric pressure data

Patent metadata

Field	Value
Publication number	US-9766065-B2
Application number	US-201313840050-A
Country	US
Kind code	B2
Filing date	Mar 15, 2013
Priority date	Mar 15, 2013
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A technique for reducing altitude error involves determining a corrected altitude for an aircraft using forecast atmospheric pressure data available, for example, from a weather forecasting service. The forecast atmospheric pressure data includes, for a number of points in time and for a number of geographic locations, a set of pressure levels and corresponding altitude values. Altitude correction data is periodically calculated from the forecast atmospheric pressure data for each of a number of geographic grid points. Upon receiving aircraft position information and an aircraft altitude measurement for an aircraft, one or more of the geographic grid points corresponding to the aircraft position are identified, and a corrected altitude of the aircraft is determined based on the altitude correction data of the one or more geographic grid points.

First claim

What is claimed is:

1. A method for reducing altitude error in an altitude measurement made at an aircraft, the method comprising:
receiving, at a processor, forecast atmospheric pressure data for a plurality of geographic locations, the forecast atmospheric pressure data including, for each of a plurality of points in time and for each geographic location, a plurality of pressure levels corresponding to a respective plurality of altitudes;
periodically calculating via the processor, from the forecast atmospheric pressure data, altitude correction data for each of a plurality of geographic grid points in a geographic grid, the altitude correction data indicating geopotential altitudes at the geographic grid points for the points in time;
receiving the aircraft altitude measurement made at the aircraft and aircraft position information indicating an aircraft position of the aircraft;
identifying one or more of the geographic grid points corresponding to the aircraft position information;
generating a corrected altitude of the aircraft from the altitude correction data of the identified one or more geographic grid points, the corrected altitude being the geopotential altitude of the aircraft for the aircraft altitude measurement; and
reporting the corrected altitude as the altitude of the aircraft.

2. The method of claim 1 , wherein calculating the altitude correction data comprises computing, for individual geographic grid points, geopotential altitude values by interpolating between the forecast atmospheric pressure data for two points in time.

3. The method of claim 2 , wherein calculating the altitude correction data further comprises, for each of a plurality of pressure levels at individual geographic grid points, interpolating between geopotential altitude values forecasted for the two points in time at a pressure level to compute the geopotential altitude value at the pressure level.

4. The method of claim 1 , wherein:
identifying one or more of the geographic grid points comprises identifying a set of geographic grid points whose locations define a region surrounding the aircraft position; and
determining the corrected altitude of the aircraft comprises:
determining the geopotential altitude at each of the set of geographic grid points based on the aircraft altitude measurement; and
computing the geopotential altitude of the aircraft by interpolating among the geopotential altitudes at the set of geographic grid points based on a relative location of the aircraft position and the set of geographic grid points.

5. The method of claim 1 , wherein the altitude correction data comprises, for each of the geographic grid points, a plurality of geopotential altitude values for a respective plurality of pressure levels, and wherein determining the geopotential altitude at each of the set of geographic grid points comprises:
identifying first and second pressure levels corresponding to first and second geopotential altitude values bounding the aircraft altitude measurement; and
computing the geopotential altitude at each of the set of geographic grid points by interpolating between geopotential altitude values for the first and second pressure levels as a function of the aircraft altitude measurement relative to the first and second geopotential altitude values at the first and second pressure levels.

6. The method of claim 1 , wherein the altitude correction data comprises, for each of the geographic grid points, a plurality of geopotential altitude values for a respective plurality of pressure levels, and wherein determining the geopotential altitude at each of the set of geographic grid points comprises:
converting the aircraft altitude measurement to a measured pressure value based on a nominal relationship between pressure and altitude;
identifying first and second pressure levels that bound the measured pressure level; and
computing the geopotential altitude at each of the set of geographic grid points by interpolating between geopotential altitude values for the first and second pressure levels as a function of the measured pressure value relative to the first and second pressure levels.

7. The method of claim 1 , wherein the points in time include a generation time at which the forecast atmospheric pressure data were generated and future times for which atmospheric pressures are forecast beyond the generation time and generating the corrected altitude comprises:
generating, for at least one of the future times, the corrected altitude of the aircraft from the altitude correction data of the identified one or more geographic grid points.

8. The method of claim 7 , wherein calculating the altitude correction data comprises computing, for individual geographic grid points, geopotential altitude values by interpolating between the forecast atmospheric pressure data for two of the future times.

9. The method of claim 8 , wherein calculating the altitude correction data further comprises, for each of a plurality of pressure levels at individual geographic grid points, interpolating between geopotential altitude values forecasted for the two future times at a pressure level to compute a current altitude value at the pressure level.

10. The method of claim 7 , wherein the altitude correction data comprises, for each of the geographic grid points, a plurality of geopotential altitude values for a respective plurality of pressure levels for the generation time and the future times, and wherein determining the geopotential altitude at each of the set of geographic grid points comprises:
identifying first and second pressure levels corresponding to first and second geopotential altitude values bounding the aircraft altitude measurement; and
computing the geopotential altitude for the generation time and the future times at each of the set of geographic grid points by interpolating between geopotential altitude values for the first and second pressure levels as a function of the aircraft altitude measurement relative to the first and second geopotential altitude values at the first and second pressure levels.

11. The method of claim 7 , wherein the altitude correction data comprises, for each of the geographic grid points, a plurality of geopotential altitude values for a respective plurality of pressure levels for the generation time and the future times, and wherein determining the geopotential altitude at each of the set of geographic grid points comprises:
converting the aircraft altitude measurement to a measured pressure value based on a nominal relationship between pressure and altitude;
identifying first and second pressure levels that bound the measured pressure level; and
computing the geopotential altitude for the generation time and the future times at each of the set of geographic grid points by interpolating between geopotential altitude values for the first and second pressure levels as a function of the measured pressure value relative to the first and second pressure levels.

12. An apparatus to reduce altitude error in an altitude measurement made at an aircraft, the apparatus comprising:
at least one interface configured to receive:
forecast atmospheric pressure data for a plurality of geographic locations, the forecast atmospheric pressure data including, for each of a plurality of points in time and for each geographic location, a plurality of pressure levels corresponding to a respective plurality of altitudes; and
the aircraft altitude measurement made at the aircraft, and aircraft position information indicating an aircraft position of the aircraft; and

at least one processor configured to:
periodically calculate from the forecast atmosp

Assignees

• Exelis Inc

Inventors

• Garcia Michael A
• Mueller Robert
• Innis Eric
• Veytsman Boris

Classifications

• G01C5/06 Primary

  by using barometric means · CPC title

• G01B21/045 Primary

  Correction of measurements (G01B9/02055 takes precedence) · CPC title