The “High” Latitudes of Early Spanish Maps

Abstract

ABSTRACTSearch for the cause of consistently “high” latitudes on Spanish maps of the New World made prior to about 1767, indicates that crude tables, primitive instruments, and arithmetical ineptitude were not the major fault. Study of navigational methods and instruments used at that time discloses that the chief cause of error was failure to compensate for magnetic declination. Recomputation of cited values discloses the amount of this declination in the early 1700s, and this computed value agrees very closely indeed with declination values determined for that time by a variety of methods. Insertion of this recovered declination into surviving old computations reduces the latitude error from major fractions of a degree (“high”) to a very few minutes.