The 6-axis position and attitude of an imaging vehicle's detector assembly is measured by mounting the detector assembly on a compliant isolator and separating the main 6-axis IMU on the vehicle from a secondary IMU comprising at least inertial rate sensors for pitch and yaw on the detector assembly. The compliant isolator couples low-frequency rigid body motion of the vehicle below a resonant frequency to the isolated detector assembly while isolating the detector assembly from high-frequency attitude noise above the resonant frequency. A computer processes measurements of the 6-axis rigid body motion and the angular rate of change in yaw and pitch of the isolated detector assembly to mitigate the drift and noise error effects of the secondary inertial rate sensors and estimate the 6-axis position and attitude of the detector assembly.