A navigation system includes an IMU, a navigation estimator configured to estimate a current navigation solution based on (i) a last navigation solution, and (ii) a specific force vector and a n angular rate vector measured by the IMU, an RI sensor, an RI data preprocessor configured to: perform a priori transformations of last RI data and current RI data to obtain transformed last RI data and transformed current RI data based on the last navigation solution and the current navigation solution, respectively, an RI filter manager (RFM) configured to construct a delta pose registration cost gradient (DPRCG) measurement based on (i) the transformed last RI data, (ii) the transformed current RI data, (iii) the current navigation solution, and (iv) the last navigation solution. The navigation estimator is further configured to determine an absolute navigation solution based on at least (i) the current navigation solution, and (ii) the DPRCG measurement.