![]() The ellipsoid is flattened at the poles, relative to the sphere, by about 1 part in 300. When defining map projections then, it is common to approximate the surface of the earth with a simpler surface such as an ellipsoid or sphere. The surface of constant geopotential referred to as mean sea level or the geoid is quite complicated and its mathematical form is correspondingly complex. ![]() The derivation of a map transformation requires a mathematical representation of the surface of the Earth. The curved surface is usually the surface of the Earth and the plane is what we call a map. Concepts MapsĪ map projection is a procedure or mathematical formula to transform a curved surface onto a plane. Along with comments in the source code, it also describes the format of the map and grid parameter files. The purpose of this document is to give a brief introduction to mapping, gridding, and the associated terminology used in the Mapx library at NSIDC. ![]() The location is also constant, which makes it easy to compare data from different sensors or different time periods. Grids are an efficient means of storing data because the location of a value within the grid is implicit-it is not explicitly stored in the grid. Satellite remote sensing has made possible the collection of data over large areas of the Earth.
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