German main elevation network
The German Main Height Network ( DHHN2016 ) is a precise leveling network of measured height differences to establish a uniform height reference system in Germany. It goes back to a decision of the plenum of the AdV at the 116th meeting in Bonn in 2005, which provides for the renewal of the DHHN in the period 2006–2011 and which entrusts the spatial reference working group with further detailed planning.
precursor
The oldest German altitude information related to the zero point of the Neufahrwasser level near Danzig or in Schleswig-Holstein to the zero point of the level in Hamburg . They were gradually transferred to a uniform height system.
Elevation systems in the German Main Elevation Network (DHHN)
Original level
The first precision leveling took place in 1868 and was continuously improved. These go back to a decision of the Second Degree Measurement Conference in 1867 to carry out geometric precision levels instead of trigonometric main levels . The measurements, also known as original leveling , were continued in northern Germany (as part of the Prussian new admission ), Alsace-Lorraine and Hohenzollern until 1894 and expanded into a total height network. Heights of this loop leveling (mean final error ± 2.04 mm / km), which refer to the normal height point 1879, are referred to as height above sea level (heights above sea level in the old system).
DHHN12
Before the Berlin observatory was demolished in 1912, five underground fixtures (UF) (special construction for height control point) in Hoppegarten near Müncheberg (40 km from the city center of Berlin, 24 km from today's city limits) replaced the normal height point in 1879 without adding the reference horizon change. In addition to these five UFs, two more simple UFs north and south were added to the three middle UFs at a distance of 100 to 300 meters. They are intended to serve as additional safeguards in the event that the UF on the road is at risk. This means that the normal high point in 1912 as a point group consists of a total of eleven underground determinations.
Since no gravity measurements were carried out for the leveling , the heights were corrected with the normal gravity . The heights above sea level obtained in this way in the new system were normal orthometric heights . This elevation system is now called DHHN12 . The status number of the system is 100.
SNN56
In the GDR normal heights were under the name heights above zero height ( HN use) (mnemonic: " H onecker- N ull" ). They were initially implemented by the state leveling network from 1956 (SNN56). The measurements in the first-order leveling network were carried out from 1954 to 1956. The reference level was taken from the connection level of the Uniform Precision Leveling Network (EPNN) of the Eastern European countries, the Kronstadt level , a Baltic Sea level near St. Petersburg, with regard to the Krassowski ellipsoid . SNN56 heights are also referred to as heights above HN56.
SNN76
After a complete renovation measurement of the State Nivellementnetzes 1st order 1974-1976 were from 1979 in the GDR , the normal heights in 1976 introduced. The state leveling network 1976 (SNN76) was compensated for and obtained its level by maintaining the normal height of the normal height point Hoppegarten from the adjustment of 1956. Thus, like the SNN56, it relates to the Kronstadt gauge . Heights in SNN76 are also referred to as heights above HN76.
DHHN85
In the years 1980 to 1985, repeated measurements were taken in the (old) Federal Republic of Germany in the German Main Elevation Network. The final evaluation of these measurements took place in 1990 as a compulsory adjustment in normal orthometric heights while maintaining the DHHN12 height of the point UF Wallenhorst.
DHHN92
DHHN92 was the elevation system that was valid in Germany until it was replaced by DHHN2016 in June 2017. Corresponding height information is marked with "NHN", example: "500 m above sea level. NHN ". The differences to the previous systems are a few millimeters in the lowlands and just under 20 cm in the Alps.
The surveying administrations of the 16 federal states of Germany decided in 1993 (after the reunification of Germany) to introduce a uniform height reference system, the DHHN92, for the old and new federal states. With connection leveling and gravity measurements between the existing altitude networks DHHN85 (old federal states) and SNN76 (new federal states), the necessary foundations for the merger to form a network were laid from 1990 to 1992. The evaluation was carried out as a compulsory adjustment of the geopotential elevation differences of the involved leveling lines while recording the geopotential elevation of the REUN / UELN junction No. 230 at the New St. Alexander Church in Wallenhorst near Osnabrück, which was assumed to be free of errors .
The final working heights in the DHHN92 were calculated as normal heights according to Molodenski's theory by dividing the geopotential heights available at points by the individually calculated normal gravity value. The normal gravity formula of the GRS80 and point coordinates in the ETRS89 were used. Heights in DHHN92 therefore refer to the quasigeoid that was calculated with the parameters of the GRS80 and that runs through the zero point of the former Amsterdam level. With this, the DHHN92 was determined at the same reference level as the pan-European leveling networks.
To distinguish between heights of the previous DHHN versions, DHHN92 heights are called heights above normal height zero (heights above sea level). The status number of the altitude system is 160.
The subordinate lines of the leveling nets were also evaluated in DHHN92 and this height reference system has thus been implemented throughout Germany. The federal states have gradually introduced the DHHN92 as the official height reference system.
Due to natural and man-made changes in height, regular renewal of the nets is necessary in order to maintain the practical accuracy of official height control points. Due to the high age of the leveling on which the DHHN92 is based, the land surveying authorities are working on a jointly organized campaign to renew the 1st order of the DHHN. A campaign started in 2006 and was completed in 2011.
DHHN2016
DHHN2016 is the height system adopted on September 21, 2016 by the Working Group of the Land Surveying Administrations (AdV) and introduced in Germany on June 30, 2017. It is part of the Integrated Spatial Reference 2016 . It is a new measurement of the first-order leveling network with deviations from DHHN92 in the range of up to a few centimeters.
To distinguish between heights of the previous DHHN versions, DHHN2016 heights are referred to as heights above normal height zero (NHN) in DHHN2016 . The altitude system is marked with the status number 170.
Comparison of the systems in Germany
Height specifications according to DHHN12 (NN) are 12 to 16 cm higher than those according to SNN76 (HN), depending on the location. The maximum deviations of the first-order leveling points are 16 cm.
The difference between heights according to DHHN92 (NHN) and DHHN12 (NN) is between -80 mm and +42 mm, with an average of 4 mm. It is larger in the Alps than in the flat northern Germany. Therefore, DHHN12 (NN) and DHHN92 (NHN) are approximately the same in these areas. Rounding height information can lead to apparent deviations in the meter range. However, due to new measurements as part of the conversion, deviations of +59 cm ( Zugspitze ) have already occurred.
DHHN92 heights are given the addition NHN. For technical layout reasons (number of characters), NHN is sometimes unofficially abbreviated to NH, which can lead to confusion with HN information of the systems SNN56 and SNN76 . Out of habit, altitude information is sometimes incorrectly labeled m above sea level. NN , even if the values are actually related to zero normal height . Occasionally, however, no measured DHHN92 height information is available and the calculated values are not freely accessible. Another reason for the continued use of altitude information related to sea level is the easier comparability with historical information.
Height differences to neighboring countries
See also
Individual evidence
- ↑ Reinkensmeier, Gunthard: "Renewal of the DHHN" - the way through the AdV bodies . In: The renewal of the German main elevation network and the uniform integrated geodetic spatial reference 2016 . 2018, p. 9 , doi : 10.5675 / Raumzeichen_2016_Hauptdokument ( DHHN2016, main document [PDF; accessed on July 21, 2020]).
- ↑ The normal high point of 1912 - date point of the DHHN 2012? In: Measurement Brandenburg , 2/2005, pp. 31–39 (PDF; 1.5 MB)
- ↑ FORUM. Journal of the Association of Publicly Appointed Surveying Engineers , Issue 4/2016 (PDF), p. 2
- ↑ a b Diethelm Weber: The new all-German main height network DHHN 92 , Allgemeine Vermessungs-Nachrichten, 5/1994, pp. 179-180
- ↑ Working group of the surveying administrations of the federal states of the Federal Republic of Germany (AdV) Working group height fixed point field and gravity fixed point field (AK Niv): The repeated measurements 1980 to 1985 in the German main height network and the main height network 1985 of the Federal Republic of Germany, Bavarian Land Surveying Office, 1993, pp. 10-13
- ↑ Working group of the surveying administrations of the federal states of the Federal Republic of Germany (AdV) Working group height fixed point field and gravity fixed point field (AK Niv): German Main Height Network 1992 (DHHN 92) , Bavarian State Surveying Office, Munich 1995
- ↑ Working group of the surveying administrations of the federal states of the Federal Republic of Germany
- ↑ Working group of the surveying administrations of the federal states of the Federal Republic of Germany AdV: This is the height: New coordinates for the official spatial reference ( Memento of the original of August 18, 2017 in the Internet Archive ) Info: The archive link was inserted automatically and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ State Institute for the Environment, Measurements and Nature Conservation Baden-Württemberg: Höhensysteme in Baden-Württemberg (Homepage LUBW> Topics> Water> Running waters> Water development-hydraulic engineering-flood protection> Water survey3> News). Retrieved February 26, 2018 .
- ↑ The German Height Reference System - Federal Agency for Cartography and Geodesy Accessed on May 23, 2017
- ↑ Customer information 3/2009. (pdf; 1.1 MB) State Office for Surveying and Geoinformation Bavaria , September 2009, p. 2 , accessed on April 25, 2013 .
