1. A computer-implemented method for determining how to estimate one or more positions of a receiver, wherein the method comprises: determining whether to estimate a first latitude and a first longitude of a first position of the receiver using a first objective function that calculates an L-1 norm of residuals or a second objective function that calculates an L-2 norm of residuals, wherein the determination is based on one or more of:—(1) data specifying a geographical region in which the receiver is located, (2) data specifying whether the receiver is indoors or outdoors, or (3) data specifying whether a signal received by the receiver from a transmitter meets a predefined multipath condition.