Partitioned Update Kalman Filter

Partitioned Update Kalman Filter (PUKF) updates a prior using nonlinear measurement in parts

PUKF updates state using multidimensional measurements in parts. PUKF evaluates the nonlinearity of the measurement function within Gaussian prior by comparing the innovation covariance caused by the second order linearization to the Gaussian measurement noise. A linear transformation is applied to measurements to minimize the nonlinearity of a part of the measurement. The measurement update is applied then using only the part of the measurement that has low nonlinearity and the process is then repeated for the updated state using the remaining part of the transformed measurement until the whole measurement has been used. PUKFdoes the linearizations numerically and no analytical differentiation is required.
http://arxiv.org/abs/1503.02857