Latitude Zero (film) was launched in the early 19th century). Mackenzie takes them to Latitude Zero to deal with the serious injuries of Dr Masson. While returning to Latitude Zero, they are attacked by a rival supersubmarine, the "Black Shark", captained by Kuroi (Hikaru Kuroki), who works for a rival of Mackenzie, Dr. Malic (Romero), who is also over 200 years old and has a base at Blood Rock. Latitude Zero is a paradise hidden fifteen miles below the surface at the intersection of the Equator and the International Date Line. Gold is plentiful there and is used for protective clothing by the
Rhumb line ship's latitude could be established accurately by sightings of the Sun or stars but there was no accurate way to determine the longitude. The ship would sail north or south until the latitude of the destination was reached, and the ship would then sail east or west along the rhumb line (actually a parallel, which is a special case of the rhumb line), maintaining a constant latitude and recording regular estimates of the distance sailed until evidence of land was sighted. The surface of the Earth can be understood mathematically as a Riemann sphere, that is, as a projection of