Uniform co-ordinate

The basis for Finland's national mapping and for defining horizontal co-ordinates is the national grid co-ordinate system, which is abbreviated as KKJ. This grid co-ordinate system is based on the Gauss-Krüger projection. Co-ordinates according to the KJJ can be defined and presented either in the basic co-ordinate system or in the uniform co-ordinate system (YKJ). Co-ordinates in the uniform co-ordinate system are referred to as uniform co-ordinates.

In the national grid co-ordinate system the area of Finland is divided into six 3-degree wide projection zones or bands. In practice, there are four bands because the outermost ones are located right in the eastern and western borders of the country.
The central meridians of four bands are 21, 24, 27 and 30 degrees east longitude. The projection bands are at their widest in Southern Finland and narrow towards the north. The easting of the location of an object is determined by its distance to the central meridian. The northing is formed of the distance to the equator.

In the basic co-ordinate system the location is described in projections according to band as so-called band co-ordinates. The uniform co-ordinate system differs from the basic co-ordinate system in that there Finland is described as one wide band in place of four bands. The central meridian of this band is 27 degrees, which is the same as the third band of the basic co-ordinate system. The uniform co-ordinate system is used when viewing the whole of Finland or areas crossing the bands of the basic co-ordinate system.

The uniform co-ordinate system is usually used as the co-ordinate system of Statistics Finland's geographic information data unless otherwise stated.