Datum and Reference Ellipsoid

Datum

The Earth is shaped like a flattened sphere. This shape is called an ellipsoid. A datum is a model of the earth that is used in mapping. The datum consists of a series of numbers that define the shape and size of the ellipsoid and it's orientation in space. A datum is chosen to give the best possible fit to the true shape of the Earth.

There are a large number of datums in use. Many of them are optimised for use in one particular part of the world. WGS-84 is an example of a datum that is used globally.

List of Datum and Their Reference Ellipsoid

Sn | Datum |   Ellipsoid | Semi-major axis  | 1/flattening | Region of use  |

1 | Adindan | Clarke 1880 | 6378249.145 | 293.465 | Burkina Faso  |

2 | Arc 1950 | Clarke 1880 | 6378249.145 | 293.465 | Botswana |

3 | Australian Geodetic 1984 | Australian National  | 6378160 | 298.25 | Australia; Tasmania |

4 | European 1950 | International 1924  | 6378388 | 297  | England; Ireland; Scotland |

5 | Korean Geodetic System | GRS 80  | 6378137  | 298.2572221 | South Korea |

6 | Leigon | Clarke 1880 | 6378249.145 | 293.465 | Ghana  |

7 | Liberia 1964 | Clarke 1880 | 6378249.145 | 293.465 | Liberia |

8 | Minna | Clarke 1880 | 6378249.145 | 293.465 | Nigeria  |

9 | Montserrat Island Astro 1958 | Clarke 1880  | 6378249.145 | 293.465 | Montserrat (Leeward Islands) |

10 | North American 1983 | GRS 80  | 6378137  | 298.2572221 | Canada |

11 | North American 1983 | GRS 80  | 6378137  | 298.2572221 | CONUS |

12 | North American 1983 | GRS 80  | 6378137  | 298.2572221 | Hawaii |

13 | North American 1983 | GRS 80  | 6378137  | 298.2572221 | Mexico; Central America |

14 | North Sahara 1959 | Clarke 1880  | 6378249.145 | 293.465 | Algeria |

15 | Observatorio Meteorologico 1939 | International 1924  | 6378388 | 297  | Azores (Corvo & Flores Islands) |

16 | Old Egyptian 1907 | Helmert 1906  | 6378200  | 298.3 | Egypt |

17 | Old Hawaiian | Clarke 1866 | 6378206.4 | 294.9786982 | Hawaii |

18 |...