A geographic coordinate system is a coordinate system that enables every location on Earth to be specified by a set of numbers, letters or symbols. A common choice of coordinates is latitude, longitude and elevation. The invention of a geographic coordinate system is generally credited to Eratosthenes of Cyrene, who composed his now-lost Geography at the Library of Alexandria in the 3rd century BC.
In the 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically-plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles, off the coast of western Africa around the Canary or Cape Verde Islands, and measured north or south of the island of Rhodes off Asia Minor.
Ptolemy credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day.
Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead. Mathematical cartography resumed in Europe following Maximus Planudes' recovery of Ptolemy's text a little before ; the text was translated into Latin at Florence by Jacobus Angelus around In , the United States hosted the International Meridian Conference, attended by representatives from twenty-five nations.
Twenty-two of them agreed to adopt the longitude of the Royal Observatory in Greenwich, England as the zero-reference line.
The Dominican Republic voted against the motion, while France and Brazil abstained. In order to be unambiguous about the direction of 'vertical' and the 'horizontal' surface above which they are measuring, map-makers choose a reference ellipsoid with a given origin and orientation that best fits their need for the area they are mapping. They then choose the most appropriate mapping of the spherical coordinate system onto that ellipsoid, called a terrestrial reference system or geodetic datum.
Datums may be global, meaning that they represent the whole Earth, or they may be local, meaning that they represent an ellipsoid best-fit to only a portion of the Earth. Points on the Earth's surface move relative to each other due to continental plate motion, subsidence, and diurnal Earth tidal movement caused by the Moon and the Sun. This daily movement can be as much as a meter. Continental movement can be up to 10 cm a year, or 10 m in a century.
A weather system high-pressure area can cause a sinking of 5 mm. Scandinavia is rising by 1 cm a year as a result of the melting of the ice sheets of the last ice age, but neighbouring Scotland is rising by only 0. The book actually willcontain certain things you need. Reading online book will be greatexperience for you. It is usually cheaper that you must buy the book in the book store. Contain of the book is really same with the printed book.
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