Daily Archives: February 12, 2008

Datum, Ellipsoid, Rhumb Line, Secant, Spheroid, Tangent and other useful terms in Map Projection

Posted on February 12, 2008 by

Datum—A reference for position on the surface of the Earth. In surveying, a datum is a reference system for computing or correlating the results of surveys. There are two principal types of datums: vertical and horizontal. A vertical datum is … Continue reading →

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GPS Receivers: Method of Operation

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A typical GPS receiver calculates its position using the signals from four or more GPS satellites. Four satellites are needed since the process needs a very accurate local time, more accurate than any normal clock can provide, so the receiver … Continue reading →

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Classes of Map Projection

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There are several ways to classify the wide variety of map projections. One of the most common classifications is by distortion characteristics: which properties of the Earth does the projection maintain? Which does it distort? Classification based on distortion characteristics … Continue reading →

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Map Projection

Posted on February 12, 2008 by

A map projection is a way to represent the curved surface of the Earth on the flat surface of a map. A good globe can provide the most accurate representation of the Earth. However, a globe isn’t practical for many … Continue reading →

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