Bruce M. Conkey
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Just like what is the best dog breed? What is the brightest light? What is the best boot? Nothing is EASY, not even finding EASY STREET!!
Geodetic datum
Latitude and longitude values can be based on different geodetic systems or datums, the most common being WGS 84, a global datum used by all GPS equipment.[n 4] Other datums are significant because they were chosen by a national cartographical organisation as the best method for representing their region, and these are the datums used on printed maps. The latitude and longitude on a map may not be the same as on a GPS receiver. Coordinates from the mapping system can sometimes be roughly changed into another datum using a simple translation. For example, to convert from ETRF89 (GPS) to the Irish Grid add 49 metres to the east, and subtract 23.4 metres from the north.[6] More generally one datum is changed into any other datum using a process called Helmert transformations. This involves converting the spherical coordinates into Cartesian coordinates and applying a seven parameter transformation (translation, three-dimensional rotation), and converting back.[1]
In popular GIS software, data projected in latitude/longitude is often represented as a 'Geographic Coordinate System'. For example, data in latitude/longitude if the datum is the North American Datum of 1983 is denoted by 'GCS North American 1983'.
In other words, just follow the yellow brick road!
I could tell you how God takes the bumps out of the roads and I could tell you that following God won't put you on EASY STREET but life would be a lot EASIER!!
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03-19-2015 06:57 PM
