EMSE 6340 Chapter Notes - Chapter 3: Cross-Origin Resource Sharing, International Terrestrial Reference System, Cartesian Coordinate System
6 Jun 2016
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Textbook chapter 3: geodesy, datums, projections, & coord. Geodesy = science of measuring the earth"s shape. Map projection = transferring spatial data from earth"s surface onto a flat map. There can be multiple coordinates for the same point depending on the measurement technique and adjustments for measurement errors. Ensure that you are working within the same coordinate system in your work. Eratosthenes" estimate of the earth"s circumference with less than 4% error compared to the actual circumference (73). Spheroid ~ ellipsoid (various usage that seems to suggest interchangeable use, but actually, ellipsoid a class of spheroid known as oblate spheroid. Semi-major axis the longer radius in the equatorial direction (a) Semi-minor axis the shorter radius in the direction of the pole (b) The ellipsoid is flattened at the poles. The ellipsoid that best estimates the earth depends on where (i. e. which country/local area) the semi-minor and semi-major axis are measured/estimated.
