"Dead reckoning” (in navigation) is an interesting use of dead - I think it’s been around quite a while, and I cannot see any obvious rationale for its use

On the etymology of “dead reckoning” there is an interesting article at straightdope.com. 

Wikipedia offers:

“...According to the Oxford English Dictionary, the phrase dead reckoning dates from Elizabethan times (1605–1615).  The popular etymology from deduced is not documented in the OED or any other historical dictionary. It is not clear what ‘dead’ might mean in the context of dead reckoning, and several alternative theories have been promulgated....”