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ISO 6709, Standard representation of geographic point location by coordinates, is the international standard for representation of latitude, longitude and altitude for geographic point locations. The first edition ( ISO 6709:1983 ) was developed by ISO/IEC JTC 1 /SC 32.
Informally, specifying a geographic location usually means giving the location's latitude and longitude. The numerical values for latitude and longitude can occur in a number of different units or formats: [2] sexagesimal degree: degrees, minutes, and seconds : 40° 26′ 46″ N 79° 58′ 56″ W
The reverse conversion is harder: given X-Y-Z can immediately get longitude, but no closed formula for latitude and height exists. See "Geodetic system." Using Bowring's formula in 1976 Survey Review the first iteration gives latitude correct within 10-11 degree as long as the point is within 10,000 meters above or 5,000 meters below the ellipsoid.
Geodetic latitude measures how close to the poles or equator a point is along a meridian, and is represented as an angle from −90° to +90°, where 0° is the equator. The geodetic latitude is the angle between the equatorial plane and a line that is normal to the reference ellipsoid.
The precision of the latitude part does not increase so much, more strictly however, a meridian arc length per 1 second depends on the latitude at the point in question. The discrepancy of 1 second meridian arc length between equator and pole is about 0.3 metres (1 ft 0 in) because the earth is an oblate spheroid .
Primarily from the United States Government Printing Office Style Manual. [1] State names usually signify only parts of each listed state, unless otherwise indicated. Based on the BLM manual's 1973 publication date, and the reference to Clarke's Spheroid of 1866 in section 2-82, coordinates appear to be in the NAD27 datum.
For placenames in the UK, Streetmap.co.uk is very useful for clicking on a precise point to show the coordinates. Near the foot of a page displaying a map is a link "Click here to convert/measure coordinates" which takes you to a "Grid Conversion Results" page with the WGS84 latitude and longitude amongst other useful values.
Address geocoding, or simply geocoding, is the process of taking a text-based description of a location, such as an address or the name of a place, and returning geographic coordinates, frequently latitude/longitude pair, to identify a location on the Earth's surface. [1]