Abstract: A method of determining the distance traveled during an event by a mobile GPS receiver. The event comprises epochs. The method comprises receiving pseudorange data comprised of one of pseudorange differences or range rates. Each pseudorange difference, in turn, comprises a difference between a first pseudorange and a second pseudorange. The first pseudorange comprises the pseudorange between the receiver and a GPS satellite at a first epoch. The second pseudorange comprises the pseudorange between the receiver and the GPS satellite at a second epoch. The range rates comprise a range rate measurement taken by the receiver of the GPS satellite from the first epoch to the second epoch. Line-of-sight data comprised of at least one normalized vector between the receiver and the GPS satellite is then determined. Based on the pseudorange and line-of-sight data, incremental distance data is then determined. A sum over the event of the incremental distance data is then determined.

Abstract: A method of using altitude information to arrive at a more accurate GPS position. A 3D GPS position is used as an initial estimate. The latitude and longitude of the initial estimate are used to retrieve an altitude from a database. This altitude is used to calculate a 2D GPS position. The 2D GPS position is then used to retrieve another altitude from the database, and the calculate-retrieve process is continued until the calculation converges.

Abstract: A system and method is disclosed for corresponding data associated with primary correction of at least one first measurement of a GPS satellite characteristic to a second measurement of the GPS satellite characteristic taken at a mobile receiver. In a preferred embodiment of the invention, a first processor is coupled to at least one wide-area GPS corrections receiver and at least one local-area GPS corrections receiver. The wide-area and local-area receivers operate to determine the first measurement and secondary data associated with correction of the determined first measurement. In operation, an estimate of the location of the mobile receiver is determined by the first processor. The availability to the mobile receiver of the secondary correction data from the wide-area and local-area GPS corrections receivers is determined, preferably based on the location estimate. From the secondary correction data, primary data representing the primary correction is determined by the first processor.