Fundamental station
Encyclopedia
A fundamental point is the geometric origin of a geodetic network
and defines the geodetic datum of a national survey.
Some fundamental stations are an astronomical or satellite geodetic observatory
. In any case, the geographic latitude and longitude
of the station is precisely determined by methods of astrogeodesy and is chosen as ellipsoidal latitude and longitude at the Earth ellipsoid
which is used to calculate the coordinates of the whole network.
Also, precise azimuths to one or two nework points are observed, and are taken over as orientated directions of these network lines. By these procedure, the polar axis of the reference ellipsoid becomes parallel to the Earth rotation
axis, and therefore the vertical deflection
of the fundamental point is zero.
The term Fundamental station is used for special observatories which combine several space
positioning techniques like VLBI, Satellite Laser Ranging
, GPS, Glonass
etc. They are the basis of Plate tectonic analyses which allow the monitoring of continental drift
rates with accuracies of mm/year.
Important fundamental stations in Europe
are
Worldwide about 30 fundamental stations are existing: about 5 in the USA and in Commonwealth of Independent States
countries, 2-3 in South America, Africa, Eastern Asia, Australia and Antarctica.
The basic coordinate system
is the ITRF
reference frame, which is related to the ICRS celestial inertial system by means of very precise Earth Orientation Parameters
(EOPs), containing polar coordinates, Nutation
- and Earth rotation
parameters. The ITRF data set is revised every 3–5 years, the actual accuracy is in the millimeter area. The ITCS is based on about 500 Quasar
s in the far universe, and on some 3000 fundamental stars of our galaxy
. The actual coordinates of the latter (FK6) were published in 2000 by the Astronomisches Rechen-Institut (ARI) in Heidelberg
.
Geodetic network
A geodetic network is a network of triangles which are measured exactly by techniques of terrestrial surveying or by satellite geodesy.In "classical geodesy" this is done by triangulation, based on measurements of angles and of some spare distances; the precise orientation to the geographic north...
and defines the geodetic datum of a national survey.
Some fundamental stations are an astronomical or satellite geodetic observatory
Observatory
An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geology, oceanography and volcanology are examples of disciplines for which observatories have been constructed...
. In any case, the geographic latitude and longitude
Longitude
Longitude is a geographic coordinate that specifies the east-west position of a point on the Earth's surface. It is an angular measurement, usually expressed in degrees, minutes and seconds, and denoted by the Greek letter lambda ....
of the station is precisely determined by methods of astrogeodesy and is chosen as ellipsoidal latitude and longitude at the Earth ellipsoid
Earth ellipsoid
An Earth ellipsoid is a mathematical figure approximating the shape of the Earth, used as a reference frame for computations in geodesy, astronomy and the geosciences...
which is used to calculate the coordinates of the whole network.
Also, precise azimuths to one or two nework points are observed, and are taken over as orientated directions of these network lines. By these procedure, the polar axis of the reference ellipsoid becomes parallel to the Earth rotation
Earth rotation
Earth's rotation is the rotation of the solid Earth around its own axis. The Earth rotates towards the east. As viewed from the North Star Polaris, the Earth turns counter-clockwise.- Rotation period :...
axis, and therefore the vertical deflection
Vertical deflection
The vertical deflection at a point on the earth is a measure of how far the direction of the local gravity field has been shifted by local anomalies such as nearby mountains....
of the fundamental point is zero.
The term Fundamental station is used for special observatories which combine several space
Space
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction. Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of a boundless four-dimensional continuum...
positioning techniques like VLBI, Satellite Laser Ranging
Satellite laser ranging
In satellite laser ranging a global network of observation stations measure the round trip time of flight of ultrashort pulses of light to satellites equipped with retroreflectors...
, GPS, Glonass
GLONASS
GLONASS , acronym for Globalnaya navigatsionnaya sputnikovaya sistema or Global Navigation Satellite System, is a radio-based satellite navigation system operated for the Russian government by the Russian Space Forces...
etc. They are the basis of Plate tectonic analyses which allow the monitoring of continental drift
Continental drift
Continental drift is the movement of the Earth's continents relative to each other. The hypothesis that continents 'drift' was first put forward by Abraham Ortelius in 1596 and was fully developed by Alfred Wegener in 1912...
rates with accuracies of mm/year.
Important fundamental stations in Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
are
- GrasseGrasse-See also:*Route Napoléon*Ancient Diocese of Grasse*Communes of the Alpes-Maritimes department-External links:*...
, central FranceFranceThe French Republic , The French Republic , The French Republic , (commonly known as France , is a unitary semi-presidential republic in Western Europe with several overseas territories and islands located on other continents and in the Indian, Pacific, and Atlantic oceans. Metropolitan France... - GrazGrazThe more recent population figures do not give the whole picture as only people with principal residence status are counted and people with secondary residence status are not. Most of the people with secondary residence status in Graz are students...
-Lustbühel (AustriaAustriaAustria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...
) - MalvernMalvern, WorcestershireMalvern is a town and civil parish in Worcestershire, England, governed by Malvern Town Council. As of the 2001 census it has a population of 28,749, and includes the historical settlement and commercial centre of Great Malvern on the steep eastern flank of the Malvern Hills, and the former...
, England (?) - OnsalaOnsalaOnsala is a locality situated in Kungsbacka Municipality, Halland County, Sweden, with 11,375 inhabitants in 2005. It is also the biggest peninsula in Sweden, south of Gothenburg....
(large Radio telescopeRadio telescopeA radio telescope is a form of directional radio antenna used in radio astronomy. The same types of antennas are also used in tracking and collecting data from satellites and space probes...
), Sweden - Wettzell (20m Radio telescope) in the Bayerischer Wald, GermanyGermanyGermany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
- ZimmerwaldZimmerwaldZimmerwald was until 31 December 2003 an independent municipality in the Canton of Bern, Switzerland. It is located on a hill in the proximity of the city of Bern in the Bernese Mittelland...
near Berne, SwitzerlandSwitzerlandSwitzerland name of one of the Swiss cantons. ; ; ; or ), in its full name the Swiss Confederation , is a federal republic consisting of 26 cantons, with Bern as the seat of the federal authorities. The country is situated in Western Europe,Or Central Europe depending on the definition....
.
Worldwide about 30 fundamental stations are existing: about 5 in the USA and in Commonwealth of Independent States
Commonwealth of Independent States
The Commonwealth of Independent States is a regional organization whose participating countries are former Soviet Republics, formed during the breakup of the Soviet Union....
countries, 2-3 in South America, Africa, Eastern Asia, Australia and Antarctica.
The basic coordinate system
Coordinate system
In geometry, a coordinate system is a system which uses one or more numbers, or coordinates, to uniquely determine the position of a point or other geometric element. The order of the coordinates is significant and they are sometimes identified by their position in an ordered tuple and sometimes by...
is the ITRF
International Terrestrial Reference System
The International Terrestrial Reference System describes procedures for creating reference frames suitable for use with measurements on or near the Earth's surface. This is done in much the same way that a physical standard might be described as a set of procedures for creating a realization of...
reference frame, which is related to the ICRS celestial inertial system by means of very precise Earth Orientation Parameters
Earth Orientation Parameters
The Earth's rotation is not even. Any motion in/on the Earth causes a slowdown or speedup of the rotation, or a change of rotation axis. Most of them can be ignored, but movements of very large mass, like sea current or tide can produce discernible changes and cause error to very precise...
(EOPs), containing polar coordinates, Nutation
Nutation
Nutation is a rocking, swaying, or nodding motion in the axis of rotation of a largely axially symmetric object, such as a gyroscope, planet, or bullet in flight, or as an intended behavior of a mechanism...
- and Earth rotation
Earth rotation
Earth's rotation is the rotation of the solid Earth around its own axis. The Earth rotates towards the east. As viewed from the North Star Polaris, the Earth turns counter-clockwise.- Rotation period :...
parameters. The ITRF data set is revised every 3–5 years, the actual accuracy is in the millimeter area. The ITCS is based on about 500 Quasar
Quasar
A quasi-stellar radio source is a very energetic and distant active galactic nucleus. Quasars are extremely luminous and were first identified as being high redshift sources of electromagnetic energy, including radio waves and visible light, that were point-like, similar to stars, rather than...
s in the far universe, and on some 3000 fundamental stars of our galaxy
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
. The actual coordinates of the latter (FK6) were published in 2000 by the Astronomisches Rechen-Institut (ARI) in Heidelberg
Heidelberg
-Early history:Between 600,000 and 200,000 years ago, "Heidelberg Man" died at nearby Mauer. His jaw bone was discovered in 1907; with scientific dating, his remains were determined to be the earliest evidence of human life in Europe. In the 5th century BC, a Celtic fortress of refuge and place of...
.