A method for substituting at least one high quality position measurement of an object taken before an interrupting event with a set of upgraded low quality position measurements of the object provided by the same source of measurements after the interrupting event. The method comprises the following steps: (A) obtaining at least one high quality position measurement of the object provided by a source of measurements before the interrupting event; (B) saving at least one high quality position measurement of the object; (C) if at least one position measurement of the object provided by source of measurements after the interrupting event is of substantially high quality, using at least one position measurement of substantially high quality of the object for navigation purposes of the object; and (D) if each position measurement of the object provided by the source of measurements after the interrupting event is of low quality, and if there is not at least one restoration event; then upgrading at least one position measurement of the object by using an upgrade algorithm.