Augmentation of GPS with a barometer and a heading rate gyroscope for urban vehicular navigation

A new integrated DGPS/sensors land navigation system is introduced and examined. It incorporates barometric height and gyro heading which act as vertical and horizontal vehicle trajectory constraints to enhance position accuracy and availability in urban and forested environments where satellite signals are frequently blocked by obstructions. The concept of sensor constraint GPS navigation is briefly discussed. Decentralized two-state Kalman filters are implemented to obtain smooth sensor information and to estimate corrections. Error models for sensor input are developed to evaluate the effect of corresponding constraints. Augmented least squares and Kalman position estimators are chosen for constrained position determination. Field tests were carried out and height and heading constraint DGPS solutions are compared with unaided DGPS and barometric height aided DGPS solutions. For the cases tested, it improves the positioning availability by 24 to 35% while mostly maintaining the positioning accuracy within 10 metres DRMS. Conclusions are presented and advantages and disadvantages of this concept are discussed.