Pratap N Misra

56234147, Apr 22, 1997

Jan 24, 1995

8/377413

Pratap N. Misra - Sudbury MA

H04B 7185
G06F 1900

3644491

A satellite navigation receiver system for determining an accurate three dimensional position estimate of a movable object and initiating correction of the location of the movable object in response to the three dimensional estimate, utilizing a receiver for receiving range measurement signals from a satellite navigation system, a clock having a constant frequency drift rate for at least a predetermined period of time, and a processing scheme capable of computing clock bias estimates over a predetermined period of time including an instantaneous time, using the clock bias estimates in a quadratic function to adaptively derive a smoothed clock bias estimates over the predetermined period of time including the instantaneous time, computing a three dimensional position estimate of the movable object's position using the smoothed clock bias estimate at the instantaneous time, and determining if the three dimensional position estimates are of sufficient quality for a user's intended purpose, whereby depending on the computed three dimensional position estimates, alone or in conjunction with the determination as to whether such estimates are of sufficient quality, the movable object is moved in response thereto.

59318899, Aug 3, 1999

Jul 29, 1996

8/681896

Pratap N. Misra - Sudbury MA

Massachusetts Institute of Technology - Cambridge MA

H04B 7185
G06F 1900

701213

A satellite navigation receiver system detects faulty range measurement signals from navigation satellites and excludes them from future position estimates. This system includes a receiver coupled to a movable object. The receiver includes a stable clock with a constant frequency drift rate over a predetermined period of time. A processor coupled to the receiver models the behavior of the clock over a time period equivalent to the period of constant frequency drift rate. The processor then generates predicted clock bias estimates over a future period of time equivalent in length to the period modeled, generates an instantaneous clock bias estimate using satellite signals, and determines the difference between the instantaneous clock bias estimate and a predicted instantaneous clock bias estimate. If the difference does not fall within an acceptable limit, one or more signals are determined to be faulty. When at least five satellites are in view, the processor determines which satellites have generated the faulty signals by generating sets of position and clock bias estimates and performing four- and three-dimensional estimation to determine consistency of the sets.

61812749, Jan 30, 2001

Jun 30, 1999

9/343743

Michael M. Pratt - Bolton MA
Brian P. Burke - Lexington MA
Pratap N. Misra - Sudbury MA

Massachusetts Institute of Technology - Cambridge MA

H04B 7185

34235704

A navigation receiver system provides real-time precise relative positioning in cooperation with an associated carrier phase receiver. The navigation receiver system and the associated carrier phase receiver both sample signals during a single epoch, and the associated carrier phase receiver processes the received signals to provide and transmit first carrier phase measurement data. The navigation receiver system comprises a data link receiver that receives the first carrier phase measurement data from the associated carrier phase receiver, and a carrier phase receiver that receives carrier phase signals during the sampling epoch, and processes the carrier phase signals to provide a second carrier phase measurement data. The navigation system receiver also includes a processing unit that receives the first carrier phase measurement data and the second carrier phase measurement data and computes carrier phase difference measurements. The processing unit applies a local-minima search technique to the carrier phase difference measurements to resolve carrier phase integer ambiguities within the subspace of local minima, wherein the resolved carrier phase integers are subsequently used to determine a precise relative position of the navigation receiver system with respect to the associated carrier phase receiver.