Normal high point 1879
Coordinates: 52 ° 30 '12.4 " N , 13 ° 23' 34.9" O The normal peak 1879 (NHP 1879) marked the height reference surface normal zero , the m by definition 37,000 proceeds below this point. It was located on the north side of the New Berlin Observatory until the building was demolished in 1912. The height of the normal height point of 37 m was transferred from the Amsterdam level with an accuracy of about one centimeter by precision leveling , whereby sealevel should beabout 30 mm above the zero point of the Amsterdam level.
NHP 1879 was replaced in 1912 by the normal altitude point 1912 (NHP 1912) about 40 km east of Berlin.
Historical development
Before 1879, the height measurements within the Prussian national territory were related to different zero points chosen for the respective purpose. While a large number of authorities and private engineers counted altitude information from the zero point of a sea level, especially the Amsterdam and Swinoujscie levels, others preferred to use the mean water observed at a port in the Baltic or North Sea as a starting point. In some cases, the zero point of a nearby river level or another point that appears suitable was used as a basis for the special measurements.
The cause of this diversity was that there was a lack of a precise and coherent leveling network. Thus it was not possible to combine the measurements carried out in different parts of the country and to relate them to a common zero point.
After the precision leveling of the trigonometric department of the Prussian land survey had advanced so far that they covered the greater part of the Prussian state, namely the one lying north of the latitude of Berlin, with a coherent network, believed the head of the land survey, Lieutenant General Otto von Morozowicz , the appropriate time has come to remedy this situation and submitted a corresponding application to the Central Directory of Surveying at the meeting of December 11, 1875. A commission was thereupon charged with examining the matter more closely and preparing proposals.
In the deliberations of this commission, which met under the chairmanship of Lieutenant General von Morozowicz on October 7, 1876 and which consisted of Messrs Oberbergrat Wilhelm Hauchecorne , Building Councilor Röder, Major Oskar Schreiber , Major Steinhausen and Privy Building Councilor Adolf Wiebe , the urgent need arose of a normal height point, which as a visible designation established a zero point to be introduced for all height regulations in the Prussian state. The necessity was emphasized, for the effective implementation of a uniform basis of all leveling, to oblige all departments of the state administration to the exclusive use of this zero point.
A detailed discussion also took place about the most appropriate choice of the location for the normal altitude point. In favor of choosing a point on the coast, the intention was to use the mean water of the sea to control and define the normal altitude point. However, the mean water could only be determined by observations over several years and only under the condition that the adjacent land is not subject to any uplift or subsidence.
The commission opted for a location in a central location, not in the mountains, but on old ground that is less exposed to uplift and subsidence. The central location also made it possible to have a good connection to the surrounding leveling network. On the basis of an expert opinion by the director of the Royal Observatory in Berlin (Professor Dr. Foerster), it was decided to attach the normal height point to one of the observation pillars of the Berlin observatory (north view, see panel VI). The point should be easily adjustable from the outside with a leveling instrument.
The “mean sea level” was chosen as the altitude for the normal zero point to avoid negative altitudes. In order to define this vague term more precisely, the following was considered at the time:
- We know nothing more of the mean sea level than the so-called "mean water", which has resulted from the level observations at individual port locations over the past 20 to 30 years and whose mutual altitude has been determined by leveling the relevant levels.
- The mean sea level on the high seas is - with the currently available science and technology - not measurable. For theoretical reasons, however, the same level - both in different seas and in the same sea in different places - cannot be demonstrated, and the existence of significant level differences can hardly be doubted.
- It emerges from this that the “mean sea level” can only be spoken of in an approximate sense and that in the present case the approximate mean water on our sea coasts is to be taken.
- Of all the zero points, that of the Amsterdam level has so far been used most frequently in Prussia. Its height agrees sufficiently with the mean waters observed on our sea coasts to be taken as "mean sea level" in the sense described under 3.
For these reasons, the commission decided that the normal zero point should be brought into line with the zero point of the Amsterdam level and that this altitude should be brought about due to the connection of this level with the German leveling network that had just been completed (October 1876). Finally it was stipulated that the mark to be produced at the observatory should be named “Normal high point for the Kingdom of Prussia” and for the heights counted from normal zero the designation “Height above normal zero” or in abbreviated form “Height above NN "should be introduced.
In the meeting of December 2, 1876, the Central Directory fully endorsed the above proposals of the commission. After declarations of approval were received from the ministries in the course of 1877, in particular with regard to the mandatory introduction of the normal zero point, work on establishing the normal high point was started under the direction of the head of the trigonometric department and continued until spring Completed in 1879. Only one ministry, through its representative, the President of the Geodetic Institute, Leutnant General Baeyer , rejected the introduction. He probably couldn't get over the fact that his trigonometric leveling from Świnoujście to Berlin around 1835 was not appropriately appreciated and the Amsterdam level was decided to refer to.
For the birthday of Kaiser Wilhelm I , the formal handover of the facility took place on March 22, 1879.
Description of the plant
The building of the Royal Observatory near the Hallesches Tor in Berlin had four pillars intended for the installation of their main instruments: a central, a north, a south and a west pillar. These were - completely isolated from each other and from the walls of the building - built of bricks and two meters below the natural ground established . Since the property on which the observatory was built between 1832 and 1835 was so deep that the groundwater rose almost to the surface of the natural soil when the level was unusually high, a very wide driveway two meters high was built around the building. The foundation of the pillars was four meters below the level of the path.
The then director of the observatory, Wilhelm Foerster , commented on the experience gained since then with regard to the strength of the pillars in a report as follows:
“The systematic readings of numerous spirit levels on the pillars of the observatory, in particular the continuous observation of the position of the central pillar against the vertical and the meridian , which have been systematically carried out for over 40 years, irrefutably confirm the extraordinary durability of the building ground , although in the neighboring Bessel and Charlottenstrasse the building site is indeed an unfavorable one. The observatory has also already gone through a very important groundwater crisis without any changes in the masonry or changes in the position of the pillars against the vertical and the meridian. When the present shipping canal, which passes the Hallesches Tor, was constructed in 1848, the groundwater, the level of which had previously been observed with a float near one of the pillar foundations, suddenly and continuously sank by more than 5 feet , so that the swimmer never showed water again later. "
The normal height point was marked and defined on the north pillar of the observatory in the following way:
A 1.70 m long syenite bar (panel VII), which, with its longitudinal axis in a horizontal position, was walled into the above-mentioned pillar of the observatory, protruded with its protruding front part freely through the perforated northern outer wall of the building. On its vertical, finely ground face on a body made of white enamel glass pushed into it from above, it had a vertical millimeter scale 20 cm long, the middle line of which marked the normal height point.
The part of the beam protruding from the masonry of the pillar was 0.65 m long and its cross-section was in the form of a square, rounded at the top, 0.32 m on a side. A dovetail- shaped groove to accommodate the glass body was worked into its flat top surface (panel IX), on the visible front surface of which the scale was located. The upper part of the groove, which was not filled by the glass body, was filled with a ground-in and cemented piece of syenite. The top surface of the syenite bar (scale stone) bore the initial inscription 37 METER ABOVE NORMAL-ZERO in gold-plated bronze with reference to the center line of the scale. The height of the center bar on the ground has been chosen such that on a a (about 10 m) at a short distance in the garden of the observatory tripod located leveling the height of the line of sight could be read directly from the scale. Corresponding numbering was available for this purpose.
The housing of the normal high point and its closure had been designed and executed by the government architect Gérard in a monumental style and with an artistic decoration corresponding to the importance of the facility.
The scale stone emerging freely from the pillar of the observatory (panel VII) was walled and vaulted in the perforated wall at a distance of 8 cm from its periphery. The face of this vault was clad with a slab made of polished Strehlen granite . This was worked out according to the shape of the scale stone and surrounded the head part with a gap of 3 cm.
The opening of the granite slab was widened from the front face of the scale stone to a semicircle of 37.5 cm radius. A richly decorated bronze door (panel X) that could be opened from top to bottom, which rested in an oblong (rectangular) panel made of the same material, closed the opening in front of the scale stone. On the bronze plaque above the door was the gilded inscription NORMAL HIGH POINT FOR THE KINGDOM OF PRUSSIA and on the door itself 37 METERS ABOVE ZERO . The case for the normal high point was made of polished green Swedish granite. A bronze plaque set in its base showed the date of its establishment (March 22, 1878), one year before the inauguration.
In order to control the normal height point with regard to any change in its altitude, it was related to the west pillar of the observatory as follows: A horizontal cast-iron T-beam with an upstanding footbridge was walled into the north side of the west pillar about 0.60 m above the ground whose outer arm stepped freely through the surrounding wall. With its reinforced end protruding about 7 cm from the wall, the support encircled an agate ball with a diameter of 31 mm so that its highest point could be used to set a leveling staff . An iron lid with a lock in the form of a square box protected the brand and closed the opening in the surrounding wall. The difference in height between the contact point of this control bolt and the normal height point - at the same time as the absolute height of the NHP - was determined and coordinated with great accuracy.
The local position of the two points to one another did not allow the work to be done from one point of view. Rather, it required two setups of a leveling instrument and an auxiliary point. As such, the previously fixed in the foundation wall of the observatory and the was Nivellementnetz related height pin 3236 uses. This had been marketed to give the normal altitude point the intended altitude, which was set at 0.841 m above the height bolt. With regard to the above It was stipulated that the control bolt should have the same height as the height bolt.
monument
The monument at the southern end of Enckestrasse, which was erected exactly at the former location of the normal height point, is due to an initiative of DVW Berlin-Brandenburg e. V. (formerly D eutscher Association for V ermessungs w esen) formed and consists of an approximately 2.50 m high stele made of steel in the form of a stylized leveling rod , which is mountable and in exactly 37,000 m in height with a slit a , draw attention allowed . On the stele, the history of the high point and the German main height network is explained in German and English. The stele was erected as part of the redesign of the open spaces at the Academy Jewish Museum Berlin on behalf of the Berlin Senate Department for Urban Development and the Environment ; DVW Berlin-Brandenburg was involved as a specialist consultant in the landscape planning competition and provided the texts for the stele.
The stele was unveiled on October 26, 2012 by the then district mayor of Friedrichshain-Kreuzberg , Franz Schulz , together with representatives of the DVW Berlin-Brandenburg.
literature
- Johann Franz Encke : Astronomical observations at the Royal Observatory in Berlin. Volume 1, Berlin 1840
- Land recording: The normal high point for the Kingdom of Prussia at the Royal Observatory in Berlin. Determined by the trigonometric department of the land registry. with 7 plates, self-published by the Landesaufnahme, Berlin 1879
- Land survey: Levels of the trigonometric department of the land survey. Volume 4, self-published by the Landesaufnahme, Berlin 1880
- E. Heller, R. Wernthaler: Development and accuracy of the new German main height network. DGK Series B, Issue No. 17, Munich 1955, ISBN 3-7696-8418-4
- DVW messages in: zfv - magazine for geodesy, geoinformation and land management, issue 6/2012, Wißner Verlag
- Hans-Gerd Becker: Monument Prussian normal high point 1879 in On the trail of land surveying in Berlin and Brandenburg , 2014, Potsdam, p. 36
Web links
- Hans-Gerd Becker: "Monument Prussian Normal High Point 1879" in "On the trail of land surveying in Berlin and Brandenburg" (PDF file; 10832 kB)
Individual evidence
- ↑ retrobibliothek.de , Meyers Konversationslexikon
- ↑ S. German: What is "normal zero"? . In: Physikalische Blätter 1958, Volume 14, Issue 2, pp. 62–66. ISSN 1521-3722 doi : 10.1002 / phbl.19580140203