Providing ephemeris data and clock corrections to a satellite navigation system receiver

Abstract

A device can access scaled values and scaling factors, which are used to convert the scaled values into coefficients and residuals. The coefficients and residuals can in turn be used with time-dependent functions to reconstruct predicted ephemeris data, including clock correction data, for satellite navigation system satellites. Ephemeris data that is broadcast from any of the satellites can be used to update the calculated ephemeris data.

1 . A method of processing satellite navigation system data in a client device, said method comprising:
 accessing a first broadcast value of a first clock correction parameter associated with a first satellite, said first broadcast value received from said first satellite and corresponding to a first point in time, wherein said first clock correction parameter is used as a first coefficient in a polynomial useful for determining an amount of bias associated with a clock onboard said first satellite;   accessing a first calculated value of said first clock correction parameter, said first calculated value determined by evaluating a time-dependent first function using said first point in time as input; and   adjusting a second calculated value using the difference between said first broadcast value and said first calculated value, said second calculated value determined by evaluating said first function using as input a second point in time that is after said first point in time.   
     
     
         2 . The method of  claim 1  further comprising:
 accessing a second broadcast value of a second clock correction parameter associated with said first satellite, said second broadcast value received from said first satellite and corresponding to said first point in time; 
 accessing a second calculated value of said second clock correction parameter, said second calculated value determined by evaluating a time-dependent second function using said first point in time as input; and 
 adjusting said second calculated value using said second broadcast value and a calculated amount of clock drift at said first point in time, said calculated amount of clock drift determined by evaluating a time-dependent third function using said first point in time as an input. 
 
     
     
         3 . The method of  claim 1  further comprising:
 accessing a pseudo-range from said client device to a second satellite at an epoch; 
 determining a true range from said client device to said second satellite at said epoch; and 
 using a difference between said true range and said pseudo-range to determine an amount of bias at said epoch for a clock onboard said second satellite. 
 
     
     
         4 . A method of processing satellite navigation system data in a client device, said method comprising:
 accessing a first broadcast value of a first clock correction parameter associated with a first satellite, said first broadcast value received from said first satellite and corresponding to a first point in time, wherein said first clock correction parameter is used as a first coefficient in a polynomial useful for determining an amount of bias associated with a clock onboard said first satellite;   accessing a first calculated value of said first clock correction parameter, said first calculated value determined by evaluating a time-dependent first function using said first point in time as input;   accessing a second broadcast value of said first clock correction parameter, said second broadcast value received from said first satellite and corresponding to a second point in time; and   determining a value of a second clock correction parameter using said first broadcast value and said second broadcast value, wherein said second clock correction parameter is used as a second coefficient in said polynomial.   
     
     
         5 . The method of  claim 4  wherein said determining comprises:
 fitting a first-order equation to said first and second broadcast values; and 
 determining the slope of said first-order equation, said slope corresponding to said value of said second clock correction parameter. 
 
     
     
         6 . The method of  claim 4  further comprising:
 accessing a third broadcast value of said first clock correction parameter, said third broadcast value received from said first satellite and corresponding to a third point in time; and 
 determining a value of a third clock correction parameter using said first, second and third broadcast values, wherein said third clock correction parameter is used as a third coefficient in said polynomial. 
 
     
     
         7 . The method of  claim 6  wherein said determining comprises:
 fitting a second-order equation to said first, second and third broadcast values; and 
 determining the second derivative of said second-order equation, said second derivative corresponding to said value of said third clock correction parameter. 
 
     
     
         8 . The method of  claim 4  further comprising:
 accessing a pseudo-range from said client device to a second satellite at an epoch; 
 determining a true range from said client device to said second satellite at said epoch; and 
 using a difference between said true range and said pseudo-range to determine an amount of bias at said epoch for a clock onboard said second satellite.