![]() As such, their collection depends on the chosen model of the Earth. This decision normally involves allowing for some type of distortion to occur in order to minimize or eliminate distortion for one or more other properties that are essential to the map's objective.Īnother major concern that drives the choice of a projection is the compatibility of data sets (geographic information). To select a map projection, determine which of the properties is the most important for the project and select the coordinate system or map projection that best preserves that property. Some map projections are clearly better for specific purposes than others, so the purpose of a map must be considered to determine which projection should be used. Map projections can be used in a map to preserve one or more of the following properties, though never all of them simultaneously:Įach projection preserves, compromises, or approximates these properties in different ways. These useful traits of maps motivated the development of map projections. Maps can be more useful than globes in many situations: they are more compact and easier to store, they readily accommodate an enormous range of scales, they are viewed easily on computer displays, they can facilitate measuring properties of the terrain being mapped, they can show larger portions of the Earth's surface at once, and they are cheaper to produce and transport. Therefore, a map projection must have been used to create the map, and, conversely, maps could not exist without map projections. The study of map projections is the characterization of these distortions.Ī map of the earth is a representation of a curved surface on a plane. Every distinct map projection distorts in a distinct way. Since any method of representing a sphere's surface on a plane is a map projection, all map projections distort. The Mercator projection shows courses of constant bearing as straight lines.Ĭarl Friedrich Gauss's Theorema Egregium proved that a sphere cannot be represented on a plane without distortion.
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