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
International Latitude Observatory The data collected by the observatories over the years still has use to scientists, and has been applied to studies of polar motion, the physical properties of the Earth, climatology and satellite tracking and navigation. The final six observatories were located, in order of Longitude (E to W), in: International Latitude Observatory The International Latitude Observatories were a system of (originally) six observatories located near the parallel of 39° 08' north latitude. They were used to measure the variation in latitude that occurs as a result of the "wobble" of the Earth on its polar axis. The original six observatories