Swedish grid

The Swedish grid is a coordinate system that was previously used for government maps in Sweden. RT 90 is a slightly modified version of the RT 38 from 1938. RT 90 has been replaced with SWEREF 99 as the official Swedish spatial reference system.
While the system could be used with negative numbers to represent all four "quarters" of the earth, the standard application of RT 90 is only useful for the northern half of the eastern hemisphere where numbers are positive. The coordinate system is based on metric measures rooting from the crossing of the Prime Meridian and the Equator at 0,0. The Central Meridian used to be based on a meridian located at the old observatory in Stockholm, but today it is based on the Prime Meridian at Greenwich. The numbering system's first digit represents the largest distance, followed by what can be seen as fractional decimal digits. Therefore, X 65 is located halfway between X 6 and X 7.
The coordinate grid is specified using two numbers, named X and Y, X being the south–north axis and Y the west–east axis. Two seven-digit numbers are sufficient to specify a location with a one m resolution.
Example:
X=6620000 Y=1317000 denotes a position 6620 km north of the Equator and -183 km west of the Central Meridian, which happens to be somewhere near the town center of Arvika.