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Introduction

A map datum is a reference from which measurements are made. In geodesy, a geodetic or map datum is a set of reference points on the earth's surface against which position measurements are made, and (often) an associated model of the shape of the earth (reference ellipsoid) to define a geographic coordinate system. Some examples of geodetic datums are: NAD27, NAD83, ED50 etc...

### Parameters

An map datum can be defined in the Eye4Software Coordinate Calculator or Eye4Software GPS Toolkit using 7 parameters, also called Helmert-7 parameters:

- Scale Factor;
- Translation X ( tX );
- Translation Y ( tY );
- Translation Z ( tZ );
- Rotation X ( rX );
- Rotation Y ( rY );
- Rotation Z ( rZ );

Also an ellipsoid has to be specified when a map datum is defined.

### Map Datum EPSG#4041 - Unknown datum based upon the Average Terrestrial System 1977 ellipsoid

### Datum Transformation Parameters Unknown datum based upon the Average Terrestrial System 1977 ellipsoid (to WGS84 datum)

Parameter |
Value |

EPSG # |
4041 |

Map Datum Name |
Unknown datum based upon the Average Terrestrial System 1977 ellipsoid |

Ellipsoid Name |
Average Terrestrial System 1977 |

Conversion |
None |

### Ellipsoid Parameters ( Average Terrestrial System 1977 Ellipsoid )

Parameter |
Value |

Semi Major Axis |
6378135 |

Inverse Flatenning |
298.257 |

Back to index of all map datums...