Patent ID: 6957143

Claim:
A method for monitoring the substitution of at least one high quality position measurement with a set of upgraded low quality position measurements, said method comprising the steps of: (A) selecting a high quality source of position measurements of an object from a group of high quality sources; (B) obtaining at least one high quality position measurement of said object using said selected high quality source; (C) saving said at least one high quality position measurement of said object; (D1) selecting a low quality source of position measurements of said object from a group of low quality sources; (D2) obtaining at least one low quality position measurement of said object using said selected low quality source; (E) substantially continuously monitoring and checking if said at least one high quality position measurement of said object is of substantially high quality; (F) if said at least one high quality position measurement of said object is of substantially high quality, using said at least one high quality position measurement of said object for navigation purposes of said object; (G) if each at least one available high quality position measurement of said object is not of substantially high quality, and if each said low quality position measurement of said object is not of substantially high quality, upgrading said at least one low quality position measurement of said object by using at least one previously saved high quality position measurement of said object to obtain at least one upgraded low quality position measurement of said object; (H) using said at least one upgraded low quality position measurement of said object in place of said at least one high quality position measurement of said object for navigation purposes, if each said upgraded low quality position measurement of said object is of substantially high quality; and (I) repeating said steps (A–H); wherein said at least one low quality position measurement of said object includes a low quality epoch timing coordinate indicative of when said at least one low quality position measurement of said object was taken; and wherein said low quality position measurement of said object is not of said substantially high quality if said low quality position measurement of said object includes an unacceptable error in said low quality position measurement of said object, or is not substantially recent.