Unpublished report to the National Snow and Ice Data Center, Boulder, Colorado USA.ĮASE-Grid: Brodzik, M. A Mapping and Gridding Primer: Points, Pixels, Grids, and Cells. Usually requires user to understand custom projection settings 1ġ Projection difficulties arise because the projection ellipsoid and reference datum are different, and most software assume they are the same No undefined "off-the-Earth" corner cells Intersection of the four center cells, grids can be nestedĬells can be nested if the grid extent is changedĬoverage can stay the same, only the number of cells changesĬorner cell locations in azimuthal grids are undefined Comparison of EASE Grid versionsĬenter of cell, polar grids cannot be nested There are currently two EASE Grids, referred to as EASE-Grid and EASE-Grid 2.0. Since areas don't change between grid cells, visualization and intercomparison operations are greatly simplified and analysis is more convenient. The EASE Grids utilize an equal-area projection because that minimizes the amount of distortion over the poles, using the Northern and Southern Hemisphere projections, and on other key areas of the globe, using the temperate and global projections. This map suffers from both areal and shape distortion. On equal-area maps, a small circle placed anywhere on the map will always cover the same area on the globe, though the shape may be distorted. A very popular map that is neither conformal nor equal-area is the cylindrical equidistant map, also known as the lat-lon grid. from -6% at the pole to +276% at the equator. No map projection is both, and some are neither." On conformal maps, angles within a small area are reproduced accurately so a small circle on the globe will look like a small circle on the map by definition, the aspect ratio remains 1:1 everywhere, while the areal distortion varies, e.g. Knowles (1993) states that "Two of the most important characteristics of maps are whether they are conformal or equal-area. Data can be expressed as a digital array with one of many possible grid resolutions, which are defined in relation to one of four possible projections: Northern / Southern Hemispheres (Lambert's equal-area, azimuthal), temperate zones (cylindrical, equal-area), or global (cylindrical, equal-area). The Equal-Area Scalable Earth (EASE) Grids are intended to be versatile formats for global-scale gridded data, including remotely sensed data. Exchange for Observations and Local Knowledge of the Arctic (ELOKA).
NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC).
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