It's also interesting that they are not teaching/using printed tables. They enter the readings into a computer to calculate the location... assuming the computer has not been EMP'd or hacked. It's much harder to EMP/hack a book. I was taught the subtle wonders of celestial navigation in my high-school NAVY ROTC course in the early 70's. I wrote a FORTRAN program to do the calculations on an IBM 1130. Commander was quite impressed... I was offered a chance to attend the Naval Academy.