1. A location estimation method for locating a mobile station (MS) by a plurality of base stations (BSs), comprising: analyzing a geometric distribution of the BSs to provide a list of conditional equations; rendering a geometric dilution of precision (GDOP) contour based on the analysis of the geometric distribution; allocating at least one virtual BS to a position according to the GDOPcontour, said virtual BS having a virtual distance to the MS to provide a constraint equation; and estimating the MS location based on the conditional equations and the constraint equations.