Geodesy

The main purpose of our geodetic activities is to determine co-ordinates for the location of points on the earth's surface in geodetic reference systems, elevations referred to reference surfaces and gravity values. Under the heading Geodesy there is a general description of geodesy, a glossary (in Swedish), a collection of formulae (partly in Swedish) and a FAQ page (in Swedish).

Reference systems

The geodetic description of the Earth distinguishes between three fundamental surfaces: the Earth's surface, which includes the sea surface where there are seas, is the surface on which we live; the geoid is the equipotential surface of the Earth's gravity field that best connects to the sea surface; and the Earth ellipsoid is the rotational ellipsoid that best connects to the geoid. To define the position of points on the Earth's surface we need geodetic reference systems based on these three surfaces, their internal relations and their changes over time.

• Three-dimensional systems
• Two-dimensional systems
• Height systems
• The geoid
• Gravity systems
• Postglacial land uplift

Introduction of SWEREF 99 and RH 2000

A change to a homogeneous national reference system for positioning is planned. Lantmäteriet, in cooperation with users, will further develop and implement methods for changing planar and vertical reference systems.

Map projections

For map production and several other technical applications the most practical way to define the location of points is in a plane co-ordinate system. The reference ellipsoid, or part of it, is depicted on a plane surface by a map projection. The choice of projection is steered by the need to minimize projection errors and to make the computation of projection corrections as simple as possible. Most Swedish maps are produced using the Gauss-Krüger (Transverse Mercator) projection. Under this heading there is information on most of the map projections used today and a description of the theory of map projections.

Transformations

In this context the term transformation can be generally used for all functions where one set of co-ordinates is mathematically converted from one co-ordinate system - the From (source) system - to another set of co-ordinates in another co-ordinate system - the To (destination) system. Lantmäteriet has developed a software package, Gtrans, for co-ordinate transformations. A distinction is made between defined transformation relationships, conversions, and empirical relationships which are the result of fitting between two different systems.

• Relationships and parameters
• Transformation methods
• Gtrans
• Additional software

GPS and other surveying techniques

Today, most geodetic survey work is carried out using GPS equipment. In the future, GPS will be complemented by other satellite-based systems such as Galileo and GLONASS. Galileo is the planned European equivalent of GPS, whereas the Russian equivalent, GLONASS, which comprises a limited number of satellites, is already operational. Other surveying techniques are also described under this heading.

The Geodetic Archive

Lantmäteriet's Geodetic Archive contains documents and field books dating from the end of the 1700's up to the present day. Parts of the old material were previously classified and are still kept in the Military Archives but, nowadays, the general public has access to this material. Station descriptions and sketches and lists of co-ordinates and heights can be obtained from the Geodetic Archive.

Reports/Publications

The results of much of the work carried out by Lantmäteriet's Geodetic Research Department is publishes in a series of reports (LMV-rapporter). Reports published since 2000 on can be downloaded as pdf files. Other reports are presented in a list.