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Modern positioning systems – GPS, Glonass, Galileo and Beidou – are global and therefore require three-dimensional, globally adapted reference systems.
As satellite-based surveying techniques, such as GPS, began to be adopted on an increasing scale during the 1990's, the importance of three-dimensional reference systems also began to increase.
To state a position in a three-dimensional reference system
The fundament for all spatial information is the reference system. To give positions, determination of three dimensions is required, normally in a three-dimensional right-angled coordinate system (X,Y,Z), also known as a Cartesian coordinate system. Positions can be converted into geodetic coordinates – latitude and longitude – which, together with the height above the ellipsoid, define the three-dimensional position.
Questions and answers
Latitude and longitude can be given either as decimal degrees; or degrees and decimal minutes (actually arc minutes); or degrees, minutes and decimal seconds (actually arc seconds). Hence there are three ways to enter one and the same position. See examples of a latitude below:
- Decimal degrees: 60.75350° N
- Degrees, decimal minutes: 60°45,210'N
- Degrees, minutes, decimal seconds: 60°45'12.6"N
There is an Excel sheet for conversion between the different formats (xlsx, new window).
The difference between latitude and longitude in RT 90 and globally adapted reference systems (pdf, in Swedish, new window) (SWEREF 99, WGS 84 and others) is about 100‑300 meters in Sweden.
In order for a position expressed as latitude and longitude to be unambiguous, one must specify which reference system is used.