Methods for determining an initial AINS heading

A method for determining Ak (a best initial heading estimate) for use with an alignment program running in an AINS (aided INS) computer in an AINS system using serial computing, the method comprising the steps of:

• A. moving the AINS system during a filter interval,
• B. recording N pairs of GNSS position data and INS in-motion data as N records in a first array,
• C. assigning a corresponding indexed heading ψk characterizes a predetermined indexed heading selected from a circular set of K indexed headings extending in uniform spaced relation sequence from a first indexed heading to the last indexed heading,
• D. processing each of the N records in the first array with the indexed heading ψk to obtain N horizontal position measurement residuals and saving each of the respective N horizontal position measurement residuals with its corresponding indexed heading in a second array,
• E. selecting the maximum value horizontal position measurement residual from the N horizontal position measurement residuals in the second array and save it with its corresponding index heading ψk in a third array,
• F. select the next indexed heading and if the next indexed heading is not the last indexed heading, return to step C and re-execute steps C, D, E, and F and if the next indexed heading is the last indexed heading, advance to step G and perform step G,
• G. identify the smallest horizontal position measurement residuals from the recorded maximum horizontal position measurement residuals in the third array and select the corresponding value of ψk in the third array as Ak, for use in the alignment program.

A system for determining Ak (a best initial heading estimate), running in an AINS (aided INS) computer in an AINS system using parallel computing, the system comprising:

• an IMU coupled to
• the AINS computer, the IMU being coupled to provide INS data to
• a data bus from
• a triax of accelerometers and data from
• a triax of rate gyros,
• an array of AINS engine computers coupled to the data bus to be responsive to the INS data, each AINS engine computer having
• an alignment program initialized with an indexed heading ψk characterizing a predetermined heading selected from a circular set of K indexed headings extending in a uniform spaced relation sequence from a first to a Kth or last indexed heading,
• a GNSS for providing position data to the data bus,
• each AINS engine computer being coupled to the data buss, the alignment program running in each respective AINS engine being, responsive to the INS data from the IMU, the position data from the GNSS the alignment program being further characterized to provide a series of time indexed horizontal position measurement residues in response to movement of the AINS,
• a kth AINS engine producing the smallest sum of horizontal position measurement residuals being identified as the AINS engine having been initialized with an indexed heading ψk closest in value to the Ak, best initial heading estimate.