After a bit more

research and after consulting with the

celestial navigation mafia this is what I have for Haversine vs Cosine formulas:

Haversine formula is way easier to do manually, resulting in fewer

mistakes. It has been superseded by other manual methods though.

On a computer the Cosine formula is better as long as you aren't talking about 1m distances. Even then just make sure your processor and subroutines will handle 20 significant digits and you should be fine. For

celestial navigation and/or

route planning, Cosine works just fine.

Programming-wise, Cosine formula is 1 line, Haversine is 3 lines.

Historical aside: The height of tech*nology for navigator’s calculations used to be log tables. As there is no (real) log of a negative number, the ‘versine’ enabled them to keep trig func*tions in positive numbers. Also, the sin²(θ/2) form of the haversine avoided addition (which en*tailed an anti-log lookup, the addi*tion, and a log lookup). Printed tables for the haver*sine/in*verse-haver*sine (and its log*arithm, to aid multip*lica*tions) saved navi*gators from squaring sines, com*puting square roots, etc – arduous and error-prone activ*ities.

http://www.movable-type.co.uk/scripts/latlong.html