A map is a reduced and generalized image of an area. When the convex surface of planet Earth is imaged as a flat plane, distortions are easily formed. In order to be able to describe the surface of the Earth with the least possible errors, various map projections have been developed. In different map projections, some basic feature is correct, but other features have distortions.

Maps describing Finland use a Gauss-Krüger projection, which is an example of a right-angled map projection. In it, shapes and angles correspond to reality. In a right-angled map, the shapes of states are identifiable, but it is impossible to compare their sizes. Right-angled projection is also most often used in nautical charts. If you want to compare different areas, you need to use a right-surface map projection. In it, for example, the ratios of the areas of the states are the same as in reality, but many of them are distorted in form. Distance maps use a coordinate system of the correct length, where the scale remains unchanged over the entire map area.

In addition to the projection, the coordinate system of a map is also important. The coordinate system (KKJ) used in Finnish maps is based on imitating the shape of Earth's surface. KKJ coordinates can be expressed as either geographic coordinates, that is, latitude and longitude, or as rectangular [[$ xy $]] coordinates. In addition, a nationwide unified coordinate system (CMO) is in use.

Due to the proliferation of GPS measurements, more and more attention has been paid to coordinate systems and their accuracy. Finland is in the process of using the EUREF-FIN coordinate system based on international coordinate systems, which is more accurate than at present and better suited for satellite positioning as well.

The Global Positioning System (GPS) is a system maintained by the United States Department of Defense. Its development began in 1973 for military purposes. It is based on 24 positioning satellites, the data from which can be used to determine the position of the GPS locator quite accurately. Based on the data received and the speed at which the radio waves propagate, the GPS locator calculates how far it is from the satellite. When the distance from three satellites is known, the position can be calculated. A fourth satellite is used for authentication. The system also needs ground stations for maintenance and monitoring.

GPS satellites use two different transmission frequencies, one of which is encrypted and used only by the U.S. Defense Forces. Civilian GPS, or SPS (Standard Positioning System), is less accurate than the corresponding U.S. Defense Forces GPS, or PPS (Precise Positioning System). In the past, the United States also sent an intentional interference signal on the SA (Selective Availability) civilian frequency, but this interference was stopped on May 2, 2000, resulting in a significant increase in GPS accuracy.