Method, apparatus and system for estimating user position with a satellite positioning system in poor signal conditions

A receiver for a satellite positioning system, the satellite positioning system including at least one satellite providing satellite ranging codes, the receiver having a receiver clock with an unknown receiver clock offset, the receiver able to solve for its position in signal conditions such that even if some of the navigation component of satellite ranging codes accessible to the receiver cannot be demodulated, the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for the at least one satellite can be determined, the receiver comprising:

• i) a non-volatile memory, for storing a program for solving for the receiver position;
• ii) a processor for executing the stored program;
• iii) an antenna responsive to the satellite ranging codes;
• iv) an antenna responsive to information about the at least one satellite and about the location of a nearby reference point;
• wherein the program solves for position according to the procedure including the steps of:
• a) including the system time at arrival as an independent and additional variable of the pseudorange function for each of the ranging codes, a variable in addition to the receiver position;
• b) providing estimates of the times of flight of the ranging codes and of the repeating part of the pseudoranges for the ranging codes for each of the at least one satellite;
• c) receiving information about the at least one satellite sufficient to determine the orbit of the at least one satellite, although not necessarily the position of the at least one satellite;
• and
• d) solving simultaneously for the receiver position and the system time at arrival.

A system for providing navigation solutions, comprising:

• A) a receiver for a satellite positioning system, the satellite positioning system including at least one satellite providing satellite ranging codes, the receiver having a receiver clock with an unknown receiver clock offset, the receiver able to solve for its position in signal conditions such that even if some of the navigation component of satellite ranging codes accessible to the receiver cannot be demodulated, the ranging codes can be baseband processed so that at least a repeating part of the pseudorange for each satellite can be determined, the receiver comprising:
• i) a non-volatile memory, for storing a program for solving for position;
• ii) a processor for executing the stored program;
• iii) an antenna responsive to the satellite ranging codes;
• iv) an antenna responsive to information about the at least one satellite and about the location of a nearby reference point;
• wherein the program solves for position according to the procedure including the steps of:
• a) including the system time at arrival as an independent and additional variable of the pseudorange function for each of the ranging codes, a variable in addition to the receiver position;
• b) providing estimates of the times of flight of the ranging codes and of the repeating part of the pseudoranges for each of the ranging codes;
• c) receiving information about the at least one satellite sufficient to determine the orbit of the at least one satellite, although not necessarily the position of the at least one satellite;
• and
• d) solving simultaneously for the receiver position and the system time at arrival;
• and
• B) a means of providing the information about the at least one satellite.