Introduction to Geodetic Datums
Geodetic datums define the size and shape of the earth and the origin and orientation of the coordinate systems used to map the earth. Hundreds of different datums have been used to frame position descriptions since the first estimates of the earth's size were made by Aristotle. Datums have evolved from those describing a spherical earth to ellipsoidal models derived from years of satellite measurements.
Modern geodetic datums range from flat-earth models used for plane surveying to complex models used for international applications which completely describe the size, shape, orientation, gravity field, and angular velocity of the earth. While cartography, surveying, navigation, and astronomy all make use of geodetic datums, the science of geodesy is the central discipline for the topic.
Referencing geodetic coordinates to the wrong datum can result in position errors of hundreds of meters. Different nations and agencies use different datums as the basis for coordinate systems used to identify positions in geographic information systems, precise positioning systems, and navigation systems. The diversity of datums in use today and the technological advancements that have made possible global positioning measurements with sub-meter accuracies requires careful datum selection and careful conversion between coordinates in different datums.
The earth has a highly irregular and constantly changing surface. Models of the surface of the earth are used in navigation, surveying, and mapping. Topographic and sea-level models attempt to model the physical variations of the surface, while gravity models and geoids are used to represent local variations in gravity that change the local definition of a level surface.
Datums in Use
- Hundreds of geodetic datums are in use around the world.
- The Global Positioning system is based on the World Geodetic System 1984 (WGS-84).
- Parameters for simple XYZ conversion between many datums and WGS-84 are published by the Defense mapping Agency.
What DATUM should I use ?
In the manual of the Trip Tracker you can find a list of regions with there corresponding Datums. If you live i.e in Portugal then you can select DATUM EUR-L. If you are not sure you can always select WGS84 as default DATUM
You can also manualy add a DATUM if you have the information of this new DATUM
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