1. A method of determining navigational parameters of a moving object, comprising: making pseudorange (PR) measurements at the object from signals received from ranging signal sources; making accumulated delta range (ADR) measurements at the object from signals received from the ranging signal sources; computing ADR differences between ADR measurements separated by a time interval that is greater than a time interval between consecutive ADR measurements; determining an optimal time interval between ADR measurements to be used for computing the ADR differences; and estimating at least one navigation parameter of the moving object from the PR measurements and the ADR differences.