Triangulation station

A Trigonometric point ( TP) or triangulation point, sometimes called trigonometers, is an observation point of land surveying or a larger triangle mesh. It forms, with its coordinates and its demarcation (stabilization in the terrain) an essential basis for Geodesy and Cartography.

In the topographic maps the TP are marked as small triangles. In the grounds are such points for geodetic measurements connection, their exact orientation and as benchmarks for local surveys.

High - and ground points

One distinguishes high points and ground points. High points are usually the tops of steeples ( it is usually the knob under the cross ), and other highly visible spots on tall buildings, also crosses the summit, symmetrical factory chimneys and high transmit antennas. They usually serve as a destination point and only in special cases ( Turmstube, eccentric ) as a measurement point of view, in contrast to the ground points.

These are marketable in the free area through an underground granite or steel plate, which is about 1 meter deep and in the middle of a cross mark is engraved. It will be buried as a visible " day mark" standing a pillar (long granite stone) with a square cross -section, the head protrudes about 20 cm from the soil and also contributes a bit cross, which is located just above the junction of the underground plate. In Germany the columns bear on the north side usually a triangle and on the south side, the letters " TP". In Austria, Hungary, etc. on the other hand ( Katastertriangulierung ) is " KT " engraved North Up; to the east are also pyramidal tapered "KF" stones in use.

To protect important TPs are " attached" to additional survey points in the immediate vicinity, that is insured controllable by blocking degree. For TPs in the vicinity of buildings a part of the elaborate demarcation can be omitted and, for example, secured by bolts on tower churches or "twin - stones ". For accurate measurements in the field of TP- ground point is exposed and then buried the pillars again centered on the plate. For all other purposes ( " local connection") is usually sufficient to the cross mark on the stone surface.

TP are no height fixed points. The amount of which may change through the training and digging Especially with pillars. To control the horizontal position a few savepoints are created where possible in the immediate vicinity, the distance to the TP is accurately known. In towns ground points can also be due to roads or sidewalks in small depressions, which are closed by a cover. For TPs with low priority ( 4th to 5th order, see below) are also coverable metal brands in use.

Surveying piers and Signalbauten

Some points in the network of the first order, or major control points eg dams are marketable instead of granite stones with surveying pillars, which are about 120 cm high. You must sound depth of at least 80 cm or be built directly on bedrock (frost depth ~ 60 cm). The cross-section is at least 35x35 cm, in a stainless steel or brass plate is embedded above, on which the instrument ( Universalistrument, theodolite, etc.) is placed exactly centered. Astronomical and Laplacepunkte have I.A. a larger cross section in order to establish a passage instrument or an astrolabe can. For particularly sensitive measurements - for example, on the portal points of a tunnel - a wooden platform is built to prevent the slightest pier inclination to the observer.

For compression and verification of trigonometric networks of national surveying the TP were previously marked with their own Signalbauten ( highs or measuring storms or " pyramids " ) of wood or metal. These signals were often permanently established, as it (3 to 30 km) had to be targeted for angle measurements from a distance. On particularly important TP these signals were built as towers with up to 40 m height. Because of the good visibility numerous signaling and observation towers were later discovered as lookouts and expanded:

TPs on lookout stations (selection)

• Ameisberg and mist stone in the mill and Waldviertel, Austria
• Anna tower on the Bröhn Deister, Germany
• Aubergwarte on the Auberg, Austria
• Ebersnackenturm on the Ebersnacken, Germany
• Lookout on the Eschkopf, Germany
• Lookout on the mountain Götzer ( Grosskreutz, Brandenburg, Germany ), new 2012 TP is a ground point next to it
• Hermannskogel waiting at Vienna (former fundamental point of Austria)
• Lookout tower Müggelturm on the small Müggelberg in (Berlin- Köpenick, Berlin, Germany ), new in 1961, TP is a ground point, the fundamental point of the Soldner coordinate system 18 of the Prussian estate cadastre was
• Radspitzturm on the Radspitze, Germany
• Lookout on the Sněžník ( High Schneeberg ), Czech Republic / Poland
• Bismarck Tower on the Tanecnice (dance Plan), Czech Republic

• These numerous TPs come on viewing platforms by mountain peaks.

Signalbau ( pyramid) at Dallmin in Brandenburg

TP on Barenberg ( Small Thank ) with concrete column as Auffindehilfe and protection

Pyramid signal; TP at the base of the pyramid

Lookout on the mountain Götzer

Lookout tower on the small Müggelberg

In recent years, since it determines the coordinates of new points increasingly satellite-based method (GPS ), the Signalbauten be partially dispensable. Smaller Signalbauten can occasionally still be found in mountainous countries primarily as rod signals. Survey points to hard to reach mountains in Asia or America are also signaled by " cairns ", centric built cairns, which are up to 40 km wide recognizable in the theodolite.

Monuments to TP

The National Survey with the basic trigonometric points is part of our technological history. Chance can be found at TP- places Monuments to explain the place and in memory of his technical history.

• The TP Rauenberg is the fundamental point of the German main triangle mesh ( DHDN ). He was on the earlier than "Rough mountain " or " rough mountain " named hill in Berlin's Tempelhof- Schöneberg. In 1985 a monument was erected at this location.

A number of existing TP have also been made ​​independently under monument protection, such as the trigonometric point "Bremer heap " at Drolshagen. or trigonometric point " Engelberg " in Olpe.

Networks 1st to 4th order

On the basis network of triangulation 1st order - which are around 20-50 km mutual distance - build tighter surveying networks: the network 2nd order with 10 km point distance - in the earlier usual way of working - right down to the 4th order in km intervals. From the 3rd -order the TPs are less expensive marketable because they can be produced more easily in case of destruction or the overgrowth. In Austria, Hungary and some neighboring countries, these points are marketable than about 80 cm deep -reaching granite stones and called KT- stones (after the previous cadastral triangulation of Austria - Hungary).

In Lower Saxony, some trigonometric points go back to the Hanoverian State Survey of Carl Friedrich Gauss. A special point is the TP Rauenberg: He is the fundamental point of the German main triangle mesh ( DHDN ) - analogous to the above-mentioned Hermannskogel for Austria's land surveying.