The new projection represents them more accurately. The rectangle in Web Mercator is misleading: on the earth, these lines are not the same length. Its northern edge is shorter than its southern edge. In the custom coordinate system, the shape of the neatline polygon is a trapezoid instead of a rectangle. The image below shows a comparison of the map in the new custom projected coordinate system and in Web Mercator. You want to choose a projected coordinate system in which the places and properties that are most important to your map are the least distorted. Your choice of a projected coordinate system depends on many factors, including the part of the world you are mapping, the scale of your map, and the purpose of your map. There are dozens of projections available in ArcGIS that can be configured into countless projected coordinate systems. They are usually used for maps of the entire world. Three maps, drawn with examples of conformal, equal area, and equidistant projections, overlaid with geodesic circles that demonstrate geometric distortions.Ĭompromise projections provide a representation of the earth that is not perfectly correct in any way but not badly distorted in any way either. Equidistant projections preserve distances, although only from certain points or along certain lines on the map. Equal area projections preserve area, at the expense of angles, so the shapes of some places appear skewed. But the cost of this quality is the distortion of areas and distances. Projection typesĬonformal projections preserve angles locally, so the shapes of features appear true. Each one seeks to preserve some geometric property at the expense of others. All projections distort the earth in some way. You will not find a projection that is suitable for all maps.
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