The NMEA FAQ (version 6.6, 30 Jan , 2008, 27KB) discusses the National Marine Electronics Association's standards for data communication between marine instruments (as used between a GPS and Autopilot, for example)
A Practical Guide to GPS by Don Bartlett discusses the use of GPS on land, with particular emphasis on the use of the UTM grid used on many topographic maps.
The OSGB FAQ by Phil Brady discusses the grid system used by the Ordnance Survey of Great Britain. Phil has provided a program to convert between OSGB coordinates and Lat/Long. It is available as BASIC source (6495 bytes) and as DOS executable (43,506 bytes).July 24/97
A NiCad Battery FAQ (33,866 bytes) discusses the charactristics of NiCad batteries, and dispels the "NiCad Memory" myth.
Ed Williams' Aviation Formulary covers great circle calculations and other topics of interest to all navigators, as well as some calculations of specific interest to aviators.