Hungarian Datum 1972 (HD72) has been established as the geodetic base of the Hungarian EOV (Unified National Projection) grid. Its classic geodetic definition can be found at the mirror of the official description directory. This kind of data is not suitable for GIS and GPS (User Datum) purposes. As the datum transformation parameters between the HD72 and the WGS84 have been published incorrectly several times (and the incorrect numbers have been mirrored on many-many websites) we summarize them correctly here.

Base ellipsoid:
GRS67 (IUGG 1967)

The Molodensky-Badekas type transformation parameters:
Direction of the transformation: HD72 » WGS84
dX= +57.01 meters
dY= –69.97 meters
dZ= –9.29 meters
Errors:
Average horizontal accuracy: 0.40 meters.
Maximum horizonal error: 1.00 meter.
Vertical accuracy: optimized.
Reference:
TIMÁR Gábor, MOLNÁR Gábor, PÁSZTOR Szilárd (2002): The Molodensky-Badekas (3-parameters) datum transformation between the WGS84 and the Hungarian Datum 1972 for practical use (in Hungarian with English summary). Geodézia és Kartográfia 54(1): 11-16.
This parameter set is accepted by the EPSG as Coordinate Transformation #1831.
For GPS receivers: in the User Datum function, the da and df parameters can be computed from the shape difference between the GRS67 and the WGS84 ellipsoids and the shift parameters should be rounded to integers as follows:
dX= +57 meters
dY= –70 meters
dZ= –9 meters
da= –23 meters
df= –0.0000001 (Note that in some receivers this number should be multiplied by 10000, resulting df=–0.0011304)

The Bursa-Wolf type transformation parameters
Direction of the transformation: HD72 » WGS84
dX= +52.684 meters
dY= –71.194 meters
dZ= –13.975 meters
eX= +0.3120 arc seconds
eY= +0.1063 arc seconds
eZ= +0.3729 arc seconds
k= +1.0191 ppm
Rotation convention: Coordinate frame rotation (most GIS packages use this one).
Errors:
Average horizontal accuracy: 0.19 meters.
Maximum horizonal error: 0.41 meters.
Vertical accuracy: optimized.
Notice: several 7-parameter sets can be defined with almost this accuracy, but take care of the signs of the parameters and the rotation convention.
Reference:
TIMÁR Gábor, MOLNÁR Gábor (2002): Standardization problems of the HD72 » ETRS89 datum transformation (in Hungarian with English summary). Geodézia és Kartográfia 54(12): 28-30.

Special thanks to Tibor BORZA and Gábor VIRÁG (Space Geodesy Observatory, Hungarian Institute of Geodesy, Cartography and Remote Sensing), for the calculation of the Bursa-Wolf parameters.

Do you have a question or a comment? Don't hesitate to mail it to G. Timár

Last modified: 30 Oct 2003