Nautical time to the zero zone, and A–M (except J) to the east and N–Y to the west (J may be assigned to local time in non-nautical applications — zones M and Y have the same clock time but differ by 24 hours: a full day). These can be vocalized using the NATO phonetic alphabet which pronounces the letter "Z" as "Zulu", leading to the use of the term "Zulu Time" for Greenwich Mean Time, or UT1 from January 1, 1972 onward. Zone Z runs from 7°30′W to 7°30′E longitude, while zone A runs from 7°30′E to 22°30′E longitude, etc. These nautical
Circle of equal altitude Circle of equal altitude The circle of equal altitude also called circle of position, CoP, is the real line of position in celestial navigation. It is defined as the locus of the Earth on which an observer sees a star, at a given time, with the same observed altitude. The center of the CoP, is the substellar point or geographical position of the observed body, and its radius is the great circle distance equal to the zenith distance of the body. The equation links the following variables formula_1 Being "B" the latitude (+N/S), "L" the longitude (+E/-W). "LHA" = "GHA"