For many years the compass
was the ONLY instrument that would, on it's own accord give a relatively accurate direction, and even at that it was not so precise that a small error in accuracy could leave you probably hundreds of miles from your destination
A latitude stick was probably worse, but at least the error in precision( or accuracy ... or both) wouldn't compound, sextants are great, but on ship? Then you have the labourous computations.
In general the compass
was what everyone had, but the declination will constantly change ... you "east" in New York
, will not be your "east" in London.
Without parameters set up with the question, there are too many variables ... and if it was as simple as following a latitude, the question should've indicated that if one were to follow the latitude at New York
, where would be the first landfall after crossing the Atlantic Ocean
... or whatever.
BTW ... about 2 GPS
on a ship ... even two "same model"(because of proprietary software), consumer-grade GPS
will give a relatively accurate True or Grid bearing, by comparing the given coordinates ... even at about 20 feet or so, since each GPS will, lose and gain the same GPS sats at the same time ... it's called differential.
But a single
GPS in the length of a 30' boat ... or even less, might jump with the loss or gain of sats ... substantially. The shorter the boat(or travel), the more off the bearing could be ... even to the point of the GPS, for a moment, saying you're going backwards or at a 90 degree deflection