Datum Transformations


A DATUM is a point, a line, or surface used as a reference in surveying and mapping. A geodetic datum is a mathematical model of the earth used to calculate the coordinates on any map.

For Important updates/corrections to published Datum Transformation Parameters click here.

To find a country and its' associated datums or a datum and its' associated countries go to the On-line Geodetic Datum Reference System.

Why is a datum important?
The main problem warfighters face is many coutries use their own datum when making their maps and doing their survey. These are referred to as local datums. The same area may have two datums giving each point two different coordinates. In addition datums generated by individual countries do not match at their boundaries. More Detail

Transformation equations and parameters provide a means of transforming coordinates referenced to one datum into coordinates referenced to a different datum.

A choice in transformation algorithm methods exist.
It is crucial that the parameters used to transform datums are consistent with the algorithm being used!
If you do not know which algorithm your software incorporates - stop and locate this information.

Types of Datum Transformations

Standard Molodensky Formula (used by NGA/TR8350.2 and GEOTRANS)

3-Parameter Transformations in GEOTRANS
7-Parameter Transformations in GEOTRANS

7-parameter Helmert (used by NATO/STANAG 2211)

Molodensky-Badekas (7+3) Transformations

 

Ellipsoid Parameters

Origins of Selected Datums

Datum, Grids, and Projections Working Group

Notice to Datum Transformation and GEOTRANS users - Aug 14, 2002

To Submit Datum Transformation Parameters

 


Point of Contact: Coordinate Systems Analysis Team
phone (314) 676-9124, DSN 846-9124
coordsys@nga.mil

Document last modified April 29, 2013