Patent ID: 7053826

Claim:
A navigation receiver method for extending fix ranges under weak signal conditions, comprising: receiving directly from an orbiting navigation satellite a codephase measurement with a half cycle ambiguity of one-millisecond about equal to a range 150-km, and a navData message that has data bit wavelength of 20-milliseconds and a half cycle ambiguity of 10-milliseconds about equal to a range 1500-km; accepting parity errors in said navData message that otherwise would prevent decoding; extracting a data bit phase from said navData message so the range of position in weak signal conditions can be extended from the range of the codephase at 150-km out to 1500-km; when a time-stamp is not available, but a measured phase of a bit transition time (BTT m ) and codephase are available, then estimating the number of data bits N set by equating a predicted range to a measured range; and outputting a position solution; wherein, when combined with a previously computed position, the measured data bit phase BTT m is used to estimate total pseudoranges when a position and timing uncertainty are each less then one-forth of the BTT range, or when a line of sight effect of each is less than ten-milliseconds for degraded conditions where the timing message cannot be reliably demodulated, to allow a positioning capability of at least ±1500-km from a previous position.