Compared to the conventional two-step localization method

the direct position determination (DPD) method has higher location accuracy.However

the DPD method is usually proposed for static target and is computationally expensive.This paper presents a novel DPD method for moving target at constant velocity based on the Doppler frequency shifts.First

the optimization model for directly determining the initial position and velocity of the emitter is constructed on the basis of maximum likelihood estimator (MLE)

and the cost function is formulated as the maximal eigenvalue of the Hermitian matrix.In order to avoid multidimensional grid search

a Newton-type iterative algorithm based on matrix eigen-perturbation theory is proposed

which involves lower computational complexity than the multidimensional grid search.In addition

the compact Cramr-Rao bound (CRB) expressions for initial position

moving velocity and track estimates are derived

which can provide a theoretical prediction for target position determination.Simulation results corroborate that the estimate variance of the proposed method is able to attain the CRB with lower computational complexity.