Daily Archives: February 12, 2008

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

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

Posted in Class Notes, Geography Practicals/Lab and Statistical Techniques, map making | 4 Comments

GPS Receivers: Method of Operation

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

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

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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