Circle of latitude circle. There are 89 integral (whole degree) circles of latitude between the equator and the Poles in each hemisphere, but these can be divided into more precise measurements of latitude, and are often represented as a decimal degree (e.g. 34.637°N) or with minutes and seconds (e.g. 22°14'26"S). There is no limit to how precisely latitude can be measured, and so there are an infinite number of circles of latitude on Earth. On a map, the circles of latitude may or may not be parallel, and their spacing may vary, depending on which projection is used to map the surface of
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