Circle of latitude the Earth onto a plane. On an equirectangular projection, centered on the equator, the circles of latitude are horizontal, parallel, and equally spaced. On other cylindrical and pseudocylindrical projections, the circles of latitude are horizontal and parallel, but may be spaced unevenly to give the map useful characteristics. For instance, on a Mercator projection the circles of latitude are more widely spaced near the poles to preserve local scales and shapes, while on a Gall–Peters projection the circles of latitude are spaced more closely near the poles so that comparisons of area will be accurate. On most non-cylindrical and non-pseudocylindrical
Latitude to radians, the arc distance is about The distance in metres (correct to 0.01 metre) between latitudes formula_7 − 0.5 degrees and formula_7 + 0.5 degrees on the WGS84 spheroid is The variation of this distance with latitude (on WGS84) is shown in the table along with the length of a degree of longitude (east-west distance): A calculator for any latitude is provided by the U.S. Government's National Geospatial-Intelligence Agency (NGA). The following graph illustrates the variation of both a degree of latitude and a degree of longitude with latitude. Historically a nautical mile was defined as the length of