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Spatial References, Coordinate Systems, Projections, Datums, Ellipsoids
posted by Satri
on Tuesday May 08, @10:55AM
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from the mastering-the-basics dept.
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from the mastering-the-basics dept.
SharpGIS offers a nice generic entry on spatial references, coordinate systems, projections, datums and ellipsoids. Even if this is things you already know, I'm sure some of your colleagues could benefit from reading it. ;-) From the text: "[...] coordinate systems are that they are all relative to the center of Earth and except the Geocentric coordinate system, uses a height system relative to the surface of the earth. This poses two immediate problems: * Where is the center of the earth * What is the shape of the earth? [...] A common statement that I hear in GIS is the following “My map doesn’t have a projection”, but this is simply not possible (unless you have a good old globe). Often people are referring to data that is in longitude/latitude and displayed on a map without applying any projection. What happens is that the system applies the simplest projection it can: Mapping Longitude directly to X and Latitude to Y. This results in an equirectangular projection, also called the “Plate Carree” projection."
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Technology: Spatial References Website 7 comments
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Kurt's Weblog links to the Spatial References website, which lists projections information in various formats. In addition to seeing existing EPSG codes, users can submit their own projections. Information for projections are translated in GML, Proj4, ESRI WKT, OGC WKT, USGS and JSON. Comments about the projections can also be shared. See also related stories below.
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