Two Body Fixes by Calculator
M. F. A’Hearn, George S. Rossano · NAVIGATION Journal of the Institute of Navigation · 1977
we present an approach to the Solution of the two body fix which utilizes all of the computing capability of a pocket calculator (non-programmable). The method results in substantial time savings over the normal approach, either by calculator or by tables, and requires no plotting, no assumed positions, and only a very rudimentary estimate of the navigator's position, the last only for correcting for motion between the times of the two sights.