Target localization and track initiation for any combination of measurement components can be performed by solving systems of simultaneous multivariate polynomials, utilizing cubature integration for covariance estimates. The solutions are approximate minimum mean squared error (MMSE) estimates. Measurement components can be monostatic/bistatic range as well as direction cosines, types of range-rate (Doppler), time delay of arrival (TDOA), and measured frequencies. Combinations of different measurement types are also considered. Results are compared to an approximate Cramer´-Rao lower bound (CRLB). No previous work has addressed initial state estimation and localization in such a wide range of problems. Simulations include three specific problems that do not appear to be solved anywhere in the literature.