	US 7,570,212 B2
	Reference beacon methods and apparatus for TDOA/FDOA geolocation
Layne D. Lommen, Auburn, Wash. (US); Henry E. Halladay, Bellevue, Wash. (US); and David O. Edewaard, Oakton, Va. (US)
Assigned to The Boeing Company, Chicago, Ill. (US)
Filed on Apr. 07, 2006, as Appl. No. 11/279,012.
Prior Publication US 2007/0236389 A1, Oct. 11, 2007
Int. Cl. G01S 1/08 (2006.01)

U.S. Cl. 342—386

17 Claims

1. A method of determining bias error in a geolocation system, comprising:

transmitting from a transmitter a reference beacon signal containing transmitter position information and transmitter motion information, wherein the transmitter motion information includes at least one of a velocity and an acceleration of the transmitter;

receiving the reference beacon signal at a plurality of collection platforms;

measuring a time of arrival of the reference beacon signal at each of the plurality of collection platforms;

determining an expected difference between the times of arrival of the reference beacon signal at two of the plurality of collection platforms based on the transmitter position information contained in the reference beacon signal;

determining a timing bias error based on the measured times of arrival of the reference beacon signal at the two collection platforms and the expected difference between the times of arrival of the reference beacon signal at the two collection platforms;

measuring a frequency of arrival of the reference beacon signal at each of the plurality of collection platforms;

determining an expected frequency difference of arrival of the reference beacon signal at the plurality of collection platforms based on the transmitter motion information contained in the reference beacon signal; and

determining a frequency bias error based on the measured frequency of arrival of the reference beacon signal at each of the plurality of collection platforms and the expected frequency difference of arrival of the reference beacon signal at the plurality of collection platforms.