Normalnull ("standard zero") or Normal-Null (short N. N. or NN ) is an outdated official vertical datum used in Germany. Elevations using this reference system were to be marked "Meter über Normal-Null" (“meters above standard zero”). Normalnull has been replaced by Normalhöhennull (short NHN).
In 1878 reference heights were taken from the Amsterdam Ordnance Datum and transferred to the New Berlin Observatory in order to define the Normalhöhenpunkt 1879. Normalnull has been defined as a level going through an imaginary point 37.000 m below Normalhöhenpunkt 1879. When the New Berlin Observatory was demolished in 1912 the reference point was moved east to the village of Hoppegarten (now part of the town of Müncheberg, Brandenburg, Germany).
Geodesy is the Earth science of accurately measuring and understanding Earth's geometric shape, orientation in space and gravitational field. The field also incorporates studies of how these properties change over time and equivalent measurements for other planets. Geodynamical phenomena include crustal motion, tides and polar motion, which can be studied by designing global and national control networks, applying space and terrestrial techniques and relying on datums and coordinate systems.
A geographic coordinate system (GCS) is a coordinate system associated with positions on Earth. A GCS can give positions:
A prime meridian is the meridian in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian form a great circle. This great circle divides a spheroid into two hemispheres. If one uses directions of East and West from a defined prime meridian, then they can be called the Eastern Hemisphere and the Western Hemisphere.
Mean sea level (MSL) is an average level of the surface of one or more of Earth's bodies of water from which heights such as elevation may be measured. The global MSL is a type of vertical datum – a standardised geodetic datum – that is used, for example, as a chart datum in cartography and marine navigation, or, in aviation, as the standard sea level at which atmospheric pressure is measured to calibrate altitude and, consequently, aircraft flight levels. A common and relatively straightforward mean sea-level standard is instead the midpoint between a mean low and mean high tide at a particular location.
The World Geodetic System (WGS) is a standard for use in cartography, geodesy, and satellite navigation including GPS. This standard includes the definition of the coordinate system's fundamental and derived constants, the ellipsoidal (normal) Earth Gravitational Model (EGM), a description of the associated World Magnetic Model (WMM), and a current list of local datum transformations.
The prime meridian is a geographical reference line that passes through the Royal Observatory, Greenwich, in London, England. It was first established by Sir George Airy in 1851, and by 1884, over two-thirds of all ships and tonnage used it as the reference meridian on their charts and maps. In October of that year, at the behest of US President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference. This conference selected the meridian passing through Greenwich as the official prime meridian due to its popularity. However, France abstained from the vote, and French maps continued to use the Paris meridian for several decades. In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana.
In computer science, a pointer is an object in many programming languages that stores a memory address. This can be that of another value located in computer memory, or in some cases, that of memory-mapped computer hardware. A pointer references a location in memory, and obtaining the value stored at that location is known as dereferencing the pointer. As an analogy, a page number in a book's index could be considered a pointer to the corresponding page; dereferencing such a pointer would be done by flipping to the page with the given page number and reading the text found on that page. The actual format and content of a pointer variable is dependent on the underlying computer architecture.
In geodesy, a reference ellipsoid is a mathematically defined surface that approximates the geoid, which is the truer, imperfect figure of the Earth, or other planetary body, as opposed to a perfect, smooth, and unaltered sphere, which factors in the undulations of the bodies' gravity due to variations in the composition and density of the interior, as well as the subsequent flattening caused by the centrifugal force from the rotation of these massive objects . Because of their relative simplicity, reference ellipsoids are used as a preferred surface on which geodetic network computations are performed and point coordinates such as latitude, longitude, and elevation are defined.
Amsterdam Ordnance Datum or Normaal Amsterdams Peil (NAP) is a vertical datum in use in large parts of Western Europe. Originally created for use in the Netherlands, its height was used by Prussia in 1879 for defining Normalnull, and in 1955 by other European countries. In the 1990s, it was used as the reference level for the United European leveling Network (UELN) which in turn led to the European Vertical Reference System (EVRS).
A geodetic datum or geodetic system is a coordinate system, and a set of reference points, used for locating places on the Earth. An approximate definition of sea level is the datum WGS 84, an ellipsoid, whereas a more accurate definition is Earth Gravitational Model 2008 (EGM2008), using at least 2,159 spherical harmonics. Other datums are defined for other areas or at other times; ED50 was defined in 1950 over Europe and differs from WGS 84 by a few hundred meters depending on where in Europe you look. Mars has no oceans and so no sea level, but at least two martian datums have been used to locate places there.
The Meades Ranch Triangulation Station is a survey marker in Osborne County in the state of Kansas in the Midwestern United States. The marker was initially placed in 1891; from 1901 to 1989, it was the reference location relative to which all locations in the United States were measured, and from 1913 to 1989, it was the reference location for all surveys in the continent.
The Berlin Observatory is a German astronomical institution with a series of observatories and related organizations in and around the city of Berlin in Germany, starting from the 18th century. It has its origins in 1700 when Gottfried Leibniz initiated the "Brandenburg Society of Science″ which would later (1744) become the Prussian Academy of Sciences. The Society had no observatory but nevertheless an astronomer, Gottfried Kirch, who observed from a private observatory in Berlin. A first small observatory was furnished in 1711, financing itself by calendrical computations.
In many countries, kilometre zero or similar terms in other languages is a particular location from which distances are traditionally measured. Historically, they were markers where drivers could set their odometers to follow the directions in early guide books.
IEEE Standard 1355-1995, IEC 14575, or ISO 14575 is a data communications standard for Heterogeneous Interconnect (HIC).
The North American Datum (NAD) is the horizontal datum now used to define the geodetic network in North America. A datum is a formal description of the shape of the Earth along with an "anchor" point for the coordinate system. In surveying, cartography, and land-use planning, two North American Datums are in use for making lateral or "horizontal" measurements: the North American Datum of 1927 (NAD 27) and the North American Datum of 1983 (NAD 83). Both are geodetic reference systems based on slightly different assumptions and measurements.
A vertical datum or height datum is a reference surface for vertical positions, such as the elevations of Earth features including terrain, bathymetry, water level, and man-made structures; in any particular case one must be assigned even if arbitrarily, and commonly adopted criteria for a vertical datum include the following approaches:
In mathematics and physics, a vector is an element of a vector space.
Normalhöhennull or NHN is a vertical datum used in Germany.
Metres above the Adriatic is the vertical datum used in Austria, in the former Yugoslavian states of Slovenia, Croatia, Bosnia-Hercegovina, Serbia, Montenegro, North Macedonia, as well as in Albania to measure elevation, referring to the average water level of the Adriatic Sea at the Sartorio mole in the Port of Trieste.
Null Island is a name for the point on the Earth's surface where the prime meridian and the equator cross, located in international waters in the Gulf of Guinea off the west African coast. In the WGS84 datum, this is at zero degrees latitude and longitude, and is the location of a buoy. The name 'Null Island' serves as both a joke based around the suppositional existence of an island there and as a name to which coordinates erroneously set to 0,0 are assigned in placenames databases in order to more easily find and fix them. The nearest land is a small islet offshore of Ghana, between Akwidaa and Dixcove at, 307.8 nmi to the north. The seabed depth at this place is around 4,940 metres (16,210 ft).
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