4. Geodetical fundamentals of the digital base map

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

e) Projecting sphere:
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:

n = 47° 10´ 00.0000" , n = 47° 07´ 20.05780".

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:

= 47° 06´ 00.0000" , = 0° 00´ 00.0000" ,
and plane coordinates: x0 = 0.0 m, y0 = 0.0 m,
as well as computed values are given the ellipsoidal geographic coordinates:
= 47° 08´ 39.8174" , n = 19° 02´ 54.8584".

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:

x = xEOV - 200 000.000 m , y = yEOV - 650 000.000 m

x increases from S to N, y from W to E.

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.

m) Area distortion:
Along the y axis:-1.4 m2/ha,
North of Hungary:+4.5 m2/ha,
South of Hungary:+4.2 m2/ha.

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