Inertial Navigation System Standardized Software Development. Volume IV. Program Listings

Section 1 of Volume 4 contains the listings of the variable precision form of the numerical simulator program, VUMSIM. In this version all the 'flight code' (i.e., simulated navigation computer operations) is performed in a user- specified floating point format, providing the capability of simulating a reduced computer word length. Appropriate library subroutines, for the specified word length, are automatically incorporated (for sine-cosine, square root, and arc tangent). The special routines called are those with names starting with the letter V. The remaining 'flight code' is modified to call the variable precision routines. The 'ideal' IMU simulator portion of the program is unchanged from NUMSIM. Section 2 contains the listings of the numerical simulator proper, NUMSIM, as described in Volume 3, without the variable precision option. Both NUMSIM and VUMSIM accept instantaneous values of specific force in the local vertical wander azimuth frame from PROFGEN at the trajectory sample rate and output the integrals of specific force in the simulated IMU frame to the 'flight code' at the appropriate attitude of navigation rate. Subsequent modifications to NUMSIM/VUMSIM, to accept integrals of specific force in the appropriate IMU frame directly from PROFGEN are described in the addendum.