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Geopositioning yields a set of geographic coordinates (such as latitude and longitude) in a given map datum. Geographic positions may also be expressed indirectly, as a distance in linear referencing or as a bearing and range from a known landmark. In turn, positions can determine a meaningful location, such as a street address.
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 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 .
Coordinate values (latitude, longitude, and altitude) should be delimited by spaces. The decimal point is a part of the value, thus must usually be configured by the operating system. [a] Multiple locations should be represented by multiple lines. Latitude and longitude should be displayed by sexagesimal fractions (i.e. minutes and seconds).
It is an alternative to referencing by geographic coordinates, which would involve two coordinates, latitude and longitude. Point features (e.g. a signpost) are located by a single distance value while linear features (e.g. a no-passing zone) are delimited by two distance values, corresponding to beginning and end.
Geographical distance or geodetic distance is the distance measured along the surface of the Earth, or the shortest arch length.. The formulae in this article calculate distances between points which are defined by geographical coordinates in terms of latitude and longitude.
However, two points with a long common prefix will be close by. In order to do a proximity search, one could compute the southwest corner (low geohash with low latitude and longitude) and northeast corner (high geohash with high latitude and longitude) of a bounding box and search for geohashes between those two.
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.