Navigator alignment using radar scan
The various technologies presented herein relate to the determination of and correction of heading error of platform. Knowledge of at least one of a maximum Doppler frequency or a minimum Doppler bandwidth pertaining to a plurality of radar echoes can be utilized to facilitate correction of the heading error. Heading error can occur as a result of component drift. In an ideal situation, a boresight direction of an antenna or the front of an aircraft will have associated therewith at least one of a maximum Doppler frequency or a minimum Doppler bandwidth. As the boresight direction of the antenna strays from a direction of travel at least one of the maximum Doppler frequency or a minimum Doppler bandwidth will shift away, either left or right, from the ideal situation.
1. A radar system located on an aircraft comprising:
a navigator component configured to:
determine Doppler frequencies and Doppler bandwidths in a plurality of radar echoes, the plurality of radar echoes collected during a scan of an antenna of the radar system;
identify at least one of a Doppler frequency or a Doppler bandwidth in the Doppler frequencies and the Doppler bandwidths;
identify an orientation of the antenna that corresponds to the at least one of the Doppler frequency or the Doppler bandwidth; and
correct a heading error of the aircraft based on the orientation of the antenna.
2. The radar system of claim 1 , wherein:
when the Doppler frequency is identified, the Doppler frequency is a maximum Doppler frequency from amongst the Doppler frequencies; and
when the Doppler bandwidth is identified, the Doppler bandwidth is a minimum Doppler bandwidth from amongst the Doppler bandwidths.
3. The radar system of claim 1 , further comprising a global positioning system (GPS) configured to generate GPS data to supplement correction of the heading error, wherein the GPS data is generated based on the orientation of the antenna.
4. The radar system of claim 3 , wherein the navigator component is further configured to determine a squint angle relating to the orientation of the antenna, and wherein the heading error of the aircraft is corrected based on the squint angle.
5. The radar system of claim 1 , wherein the heading error relates to an indicated direction determined by an inertial measurement unit (IMU).
6. The radar system of claim 5 , wherein the IMU is located on a gimbal of an antenna configured to receive the radar echoes.
7. The radar system of claim 5 , wherein the IMU is located on the body of the aircraft.
8. The radar system of claim 1 , wherein correction of the heading error comprises correction of an indicated direction determined by an inertial measurement unit (IMU) with the orientation of the antenna.
9. The radar system of claim 1 , wherein the heading error results from drift in an inertial measurement unit (IMU) configured to provide directional data relating to the front of the aircraft relative to the direction of travel of the aircraft.
10. A method, comprising:
determining for each squint angle in a plurality of squint angles, at least one of a Doppler frequency or a Doppler bandwidth for each squint angle, wherein the plurality of squint angles relating to a plurality of radar echoes being received at an antenna located on an aircraft;
determining, from the plurality of radar squint angles, a squint angle having the maximum Doppler frequency with the minimum Doppler bandwidth;
setting an actual direction of an inertial measurement unit to the squint angle having the maximum Doppler frequency with the minimum Doppler bandwidth; and
determining a heading error of the aircraft based on resolving the difference between an indicated direction for the inertial measurement unit and the set actual direction of an inertial measurement unit.
11. The method of claim 10 , wherein the inertial measurement unit is located on a gimbal of the antenna.
12. The method of claim 10 , further comprising determining a global positioning system (GPS) direction of travel for the aircraft, wherein the GPS direction of travel is based on the set actual direction of an inertial measurement unit.
13. The method of claim 12 , further comprising determining the heading error where the heading error is a function of the indicated direction for the inertial measurement unit and the GPS direction of travel.
14. The method of claim 12 , further comprising determining a resolver angle based on the angle between the front of the aircraft and a boresight of the antenna.
15. The method of claim 14 , further comprising determining the heading error where the heading error is a function of the indicated direction for the inertial measurement unit, the GPS direction of travel and the resolver angle.
16. The method of claim 10 , wherein the inertial measurement unit is located on a body of the aircraft.
17. The method of claim 10 , wherein the maximum Doppler frequency and a minimum Doppler bandwidth occurring for the squint angle aligned in the direction of travel of the aircraft.
18. A computer-readable storage medium comprising instructions that, when executed by a processor, cause the processor to perform acts comprising:
determining for each squint angle in a plurality of squint angles, at least one of a maximum Doppler frequency and a minimum Doppler bandwidth for each squint angle, wherein the plurality of squint angles relating to a plurality of radar echoes being received at an antenna located on an aircraft;
determining, from the plurality of radar squint angles, a squint angle having the maximum Doppler frequency with the minimum Doppler bandwidth;
setting an actual direction of an inertial measurement unit to the squint angle having the maximum Doppler frequency with the minimum Doppler bandwidth; and
determining a heading error of the aircraft based on resolving the difference between an indicated direction for the inertial measurement unit and the set actual direction of an inertial measurement unit.