**4.1. Projection system of the digital base map**

**a) Name:**

EOV, Uniform National Projection System

**b) Description:**

The EOV is a part of methods and systems (collection of mathematical
means and collection of parameters) for projecting of spatial
points and configurations to the plane. It provides the representation
of the territory of the whole country upon one single plane, angles
without distortion, optimization of linear and area distortion
resulted regularly from the projection (by minimizing of their
sum related to the whole country) and the use of but positive
coordinates. It contributes to the geometrical unity of surveying,
mapping and GIS activity in Hungary.

**c) Geometrical classification:**

Conformal cylindrical projection in transversal position.

**d) Reference surface:**

IUGG GRS 1967 reference ellipsoid

- semi-major axis: a=6378160 m,
- semi-minor axis: b=6356774.516 m,
- ellipsoidal geographic coordinates: ,

The projecting from the reference surface to the plane is done by inserting, the conformal Gauss spherical projection of minimum linear distortion, by means of a projecting sphere. As a projecting sphere serves the so-called Gauss-sphere fitted best to the reference ellipsoid along the normal parallel. It's radius: R=6379743.001 m, spherical geographical coordinates: ,

**f) Normal parallel:**

Parallel related to Hungary's accepted geographical latitude.
The relative ellipsoidal and spherical latitude:

**g) Origin of geographic coordinates:**

The plane of the Equator and the Greenwich Meridian.

**h) Origin of projection**

A point on the Gellérthegy Meridian, to which are related
the spherical geographic coordinates as follows:

and plane coordinates: x

as well as computed values are given the ellipsoidal geographic coordinates:

= 47° 08´ 39.8174" ,

**i) Origin of EOV plane coordinates:**

The origin of the EOV plane coordinates is chosen South-West from
the origin of projection so that each of the EOV coordinates are
positive in Hungary's territory:

**j) Projection zones:**

Single cylindrical zone covers the whole territory of Hungary in E-W direction.

**k) Scale factor:** m = 0.99993

**l) Linear distortion:**

Along the y axis: | -7 cm/km, | |

North of Hungary: | +26 cm/km, | |

South of Hungary: | +23 cm/km. |

Along the y axis: | -1.4 m^{2}/ha, | |

North of Hungary: | +4.5 m^{2}/ha, | |

South of Hungary: | +4.2 m^{2}/ha. |

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