Lowest GDOP in 2-D scenarios

Position determination in two-dimensional (2-D) scenarios is examined. The results can apply to position location in cellular systems using the system infrastructure. It is shown that the lowest possible geometric dilution of precision (GDOP) attainable from range or pseudo-range measurements to N optimally located points is 2/root N. The significance of 2/root N in bearing-only position determination is also pointed out. Contour GDOP maps demonstrate that it is worthwhile to add one absolute-range measurement (more difficult to implement) to the set of pseudo-ranges (relatively easy to implement).