**a) Name:**

Hungarian Reference System, HD-72, Hungarian Datum of 1972

**b) Description:**

The HD-72 is Geodetic Reference System ensuring
the geodetical unity of Hungary's surveying, mapping and remote
sensing activity located and relatively oriented at the Geodetic
Datum Point Szőlőhegy. Its definition was made in
the course of adjustment of the Hungarian Astrogeodetical Network
on the ellipsoid of the reference system IUGG GRS 1967 and at
the Laplace-points on the condition =
minimum set up for the deflections
of the vertical (where and are the values of the deflection of
the vertical).

**c) Reference ellipsoid:**

The ellipsoid of the reference system IUGG GRS 1967 (See chapter 4.1.)

**d) Datum station:**

- Name: Geodetic Datum Point Szőlőhegy
- Its coordinates on the reference ellipsoid:
- = 47° 17´ 32.6156" ,
- = 19° 36´ 09.9856" ,
- h = H + N = 229.24 m + 6.56 m = 235.80 m,

where

- h = the height above the ellipsoid,
- H = normal height above the Baltic-Sea level,
- N = undulation of geoid.

The ellipsoidal azimuth of the direction from the Datum Point Szőlőhegy to the control point Erdőhegy:

= 209°55´ 26.64"

Its surface geographical (astronomical) coordinates:

_{Ast} = 47°17'30.44" ,
_{Ast} = 19°36'10.18".
Surface (astronomical) azimuth of the direction from Szőlőhegy to Erdőhegy:
_{Ast} = 209°55´ 27.79".

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