Question

Which is The most important line of latitude which is used as the reference to calculate the other latitudes. What is its value?

Answer 1

Important lines of latitude:
the equator (0°)
the Tropic of Cancer (23.5° north)
the Tropic of Capricorn (23.5° south)
the Arctic circle (66.5° north)
the Antarctic circle (66.5° south)
the North Pole (90° north)
the South Pole (90° south)