  This paper considers the use of two position receivers and an inertial
measurement unit (IMU) to estimate the position, velocity, and attitude of a
rigid body, collectively called extended pose. The measurement model consisting
of the position of one receiver and the relative position between the two
receivers is left invariant, enabling the use of the invariant extended Kalman
filter (IEKF) framework. The IEKF possesses various advantages over the
standard multiplicative extended Kalman filter, such as
state-estimate-independent Jacobians. Monte Carlo simulations demonstrate that
the two-receiver IEKF approach yields improved estimates over a two-receiver
multiplicative extended Kalman filter (MEKF) and a single-receiver IEKF
approach. An experiment further validates the proposed approach, confirming
that the two-receiver IEKF has improved performance over the other filters
considered.
