Benchmark (surveying)
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The term benchmark, bench mark, or survey benchmark originates from the chiseled horizontal marks that surveyors made in stone structures, into which an angle-iron could be placed to form a "bench" for a leveling rod, thus ensuring that a leveling rod could be accurately repositioned in the same place in the future. These marks were usually indicated with a chiseled
arrow An arrow is a fin-stabilized projectile launched by a bow. A typical arrow usually consists of a long, stiff, straight shaft with a weighty (and usually sharp and pointed) arrowhead attached to the front end, multiple fin-like stabilizers c ...
below the horizontal line. The term is generally applied to any item used to mark a point as an elevation reference. Frequently, bronze or aluminum disks are set in stone or concrete, or on rods driven deeply into the earth to provide a stable elevation point. If an elevation is marked on a map, but there is no physical mark on the ground, it is a
spot height A spot height is an exact point on a map with an elevation recorded beside it that represents its height above a given datum.Whittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984, p. 506. . In the UK this is the Ordna ...
.


Purpose

The
height Height is measure of vertical distance, either vertical extent (how "tall" something or someone is) or vertical position (how "high" a point is). For example, "The height of that building is 50 m" or "The height of an airplane in-flight is abou ...
of a benchmark is calculated relative to the heights of nearby benchmarks in a network extending from a ''fundamental benchmark''. A fundamental benchmark is a point with a precisely known relationship to the
vertical datum In geodesy, surveying, hydrography and navigation, vertical datum or altimetric datum, is a reference coordinate surface used for vertical positions, such as the elevations of Earth-bound features (terrain, bathymetry, water level, and built stru ...
of the area, typically
mean sea level There are several kinds of mean in mathematics Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. ...
. The position and height of each benchmark is shown on large-scale maps. The terms "height" and "
elevation The elevation of a geographic location is its height above or below a fixed reference point, most commonly a reference geoid, a mathematical model of the Earth's sea level as an equipotential gravitational surface (see Geodetic datum § Vert ...
" are often used interchangeably, but in many jurisdictions they have specific meanings; "height" commonly refers to a local or relative difference in the vertical (such as the height of a building), whereas "elevation" refers to the difference from a nominated reference surface (such as sea-level, or a mathematical/geodetic model that approximates the sea level known as the
geoid The geoid () is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent. This surface is extended ...
). Elevation may be specified as
normal height Normal heights is a type of height above sea level introduced by Mikhail Molodenskii. The normal height H^* (or H^N) of a point is computed as the ratio of a point's geopotential number (i.e. its geopotential difference with that of sea level), by t ...
(above a reference ellipsoid),
orthometric height The orthometric height is the vertical distance ''H'' along the plumb line from a point of interest to a reference surface known as the ''geoid'', the vertical datum that approximates mean sea level. Orthometric height is one of the scientific fo ...
, or
dynamic height Dynamic height is a way of specifying the vertical position of a point above a vertical datum; it is an alternative for orthometric height or normal height. It can be computed dividing the location's geopotential number by the normal gravity at 4 ...
which have slightly different definitions.


Other types of survey marks

Triangulation point A triangulation station, also known as a trigonometrical point, and sometimes informally as a trig, is a fixed surveying station, used in geodetic surveying and other surveying projects in its vicinity. The nomenclature varies regionally: they a ...
s, also known as trig points, are marks with a precisely established horizontal position. These points may be marked by disks similar to benchmark disks, but set horizontally, and are also sometimes used as elevation benchmarks. Prominent features on buildings such as the tip of a
church Church may refer to: Religion * Church (building), a building for Christian religious activities * Church (congregation), a local congregation of a Christian denomination * Church service, a formalized period of Christian communal worship * C ...
spire A spire is a tall, slender, pointed structure on top of a roof of a building or tower, especially at the summit of church steeples. A spire may have a square, circular, or polygonal plan, with a roughly conical or pyramidal shape. Spires are ...
or a
chimney stack A chimney is an architectural ventilation structure made of masonry, clay or metal that isolates hot toxic exhaust gases or smoke produced by a boiler, stove, furnace, incinerator, or fireplace from human living areas. Chimneys are typ ...
are also used as reference points for
triangulation In trigonometry and geometry, triangulation is the process of determining the location of a point by forming triangles to the point from known points. Applications In surveying Specifically in surveying, triangulation involves only angle me ...
. In the
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
triangulation points are often set in large concrete markers that, as well as functioning as triangulation points, have a benchmark set into the side. With the increasing use of GPS and electronic distance measuring devices, the same techniques and equipment are used to fix the horizontal and vertical position of a survey marker at the same moment, and therefore the marks are usually regarded as "fixed in three dimensions". Flush brackets are metal plates placed flush into the faces of buildings or other structures. Although many are attached to triangulation pillars as above, Non-Pillar Flush Brackets were also frequently located in the faces of buildings.


Agencies responsible for benchmarks

Benchmarks are typically placed ("monumented") by a government agency or private survey firm, and many governments maintain a register of these marks so that the records are available to all. These records are usually in the form of a geographically searchable database (computer or map-based), with links to sketches, diagrams, photos of the marks, and any other technical details. Government agencies that place and maintain records of benchmarks include: *
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
**
Natural Resources Canada Natural Resources Canada (NRCan; french: Ressources naturelles Canada; french: RNCan, label=none)Natural Resources Canada is the applied title under the Federal Identity Program; the legal title is Department of Natural Resources (). is the depa ...
(Geodetic Survey Division) *
Denmark ) , song = ( en, "King Christian stood by the lofty mast") , song_type = National and royal anthem , image_map = EU-Denmark.svg , map_caption = , subdivision_type = Sovereign state , subdivision_name = Danish Realm, Kingdom of Denmark ...
**
GST GST may refer to: Taxes * General sales tax * Goods and Services Tax, the name for the value-added tax in several jurisdictions: ** Goods and services tax (Australia) ** Goods and Services Tax (Canada) ** Goods and Services Tax (Hong Kong) **G ...
( da, Geodatastyrelsen) *
France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...
**
Institut Géographique National An institute is an organisational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body. In some countries, institutes can ...
( IGN on Wiki FR). *
India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...
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Survey of India The Survey of India is India's central engineering agency in charge of Cartography, mapping and surveying.
*
Republic of Ireland Ireland ( ga, Éire ), also known as the Republic of Ireland (), is a country in north-western Europe consisting of 26 of the 32 counties of the island of Ireland. The capital and largest city is Dublin, on the eastern side of the island. A ...
** Ordnance Survey Ireland *
Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical re ...
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Istituto Geografico Militare The ''Istituto Geografico Militare'' (IGM), or Military Geographic Institute, is an Italian public organization, dependent on the Italian Army general staff (''Stato Maggiore dell'Esercito''). It is the national mapping agency for Italy. Overvie ...
*
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
**
Geospatial Information Authority of Japan The , or GSI, is the national institution responsible for surveying and mapping the national land of Japan. The former name of the organization from 1949 until March 2010 was Geographical Survey Institute; despite the rename, it retains the same ...
(GSI) *
Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...
** Netherlands Partnership Geodetic Infrastructure (NSGI) ***
Rijkswaterstaat Rijkswaterstaat, founded in 1798 as the ''Bureau voor den Waterstaat'' and formerly translated to Directorate General for Public Works and Water Management, is a Directorate-General of the Ministry of Infrastructure and Water Management of the Net ...
(vertical) *** Kadaster (horizontal) *
New Zealand New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
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Land Information New Zealand Toitū Te Whenua Land Information New Zealand (LINZ) is the public service department of New Zealand charged with geographical information and surveying functions as well as handling land titles, and managing Crown land and property. The minist ...
*
Pakistan Pakistan ( ur, ), officially the Islamic Republic of Pakistan ( ur, , label=none), is a country in South Asia. It is the world's List of countries and dependencies by population, fifth-most populous country, with a population of almost 24 ...
** Survey of Pakistan *
South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...
**
Department of Rural Development and Land Reform The Department of Rural Development and Land Reform was, from 2009 to 2019, one of the departments of the South African government. It was responsible for topographic mapping, cadastral surveying, deeds registration, and land reform. The department ...
*
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** Instituto Geográfico Nacional (IGN) *
United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the continental mainland. It comprises England, Scotland, Wales and North ...
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Ordnance Survey of Northern Ireland {{Unreferenced, date=April 2021 Ordnance Survey of Northern Ireland (OSNI) was the official mapping agency of Northern Ireland. The agency ceased to exist separately on 1 April 2008 when it became part of Land and Property Services, an executiv ...
*
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
** The
National Geodetic Survey The National Geodetic Survey (NGS) is a List of federal agencies in the United States, United States federal agency that defines and manages a national coordinate system, providing the foundation for transportation and communication; mapping an ...
(NGS; formerly U.S. Coast & Geodetic Survey) ** The
United States Army Corps of Engineers , colors = , anniversaries = 16 June (Organization Day) , battles = , battles_label = Wars , website = , commander1 = ...
(USACE) ** The
United States Forest Service The United States Forest Service (USFS) is an agency of the U.S. Department of Agriculture that administers the nation's 154 national forests and 20 national grasslands. The Forest Service manages of land. Major divisions of the agency inc ...
** The
United States Geological Survey The United States Geological Survey (USGS), formerly simply known as the Geological Survey, is a scientific agency of the United States government. The scientists of the USGS study the landscape of the United States, its natural resources, ...
(USGS)


Notable benchmarks

* The brass benchmark in the Amsterdam
Stopera The Stopera is a building complex in Amsterdam, Netherlands, housing both the city hall of Amsterdam and the Dutch National Opera and Ballet, the principal opera house in Amsterdam that is home of Dutch National Opera, Dutch National Ballet and ...
(combined city hall and opera house) is a tourist attraction, since the benchmark below the
Dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use ...
square, which has been used for the zero level of
Normaal Amsterdams Peil Amsterdam Ordnance Datum or ' (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 ', and in 1955 by other European countries. In the ...
(NAP) in the
Netherlands ) , anthem = ( en, "William of Nassau") , image_map = , map_caption = , subdivision_type = Sovereign state , subdivision_name = Kingdom of the Netherlands , established_title = Before independence , established_date = Spanish Netherl ...
, is concealed by a
manhole cover A manhole cover or maintenance hole cover is a removable plate forming the lid over the opening of a manhole, an opening large enough for a person to pass through that is used as an access point for an underground vault or pipe. It is designed t ...
. The latter benchmark has been used also for the national zero level of other countries in northwest Europe as well as for the European Vertical Reference System (EVRS). * Benchmark A in Washington, D.C. is miniature replica of the
Washington Monument The Washington Monument is an obelisk shaped building within the National Mall in Washington, D.C., built to commemorate George Washington, once commander-in-chief of the Continental Army (1775–1784) in the American Revolutionary War and the ...
. Installed in the late 1800s, this benchmark was used during the construction of the Monument and in subsequent surveys performed by the NGS. Upon completion of the monument grounds, Benchmark A was buried in a brick-lined pit and concealed by a manhole cover. In 2019, the "mini monument" was unveiled to the public for a brief time before being covered back up again.


Image gallery

USCGS-E134.jpg, C&GS benchmark disk in the
United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
Bench mark at Saint Goussaud, Limousin, France, by Institut Geographique National.jpg, Bench mark at Saint Goussaud, Limousin, France, by
Institut Géographique National An institute is an organisational body created for a certain purpose. They are often research organisations (research institutes) created to do research on specific topics, or can also be a professional body. In some countries, institutes can ...
Torontobenchmark.jpg, City of
Toronto Toronto ( ; or ) is the capital city of the Canadian province of Ontario. With a recorded population of 2,794,356 in 2021, it is the most populous city in Canada and the fourth most populous city in North America. The city is the ancho ...
benchmark disk in
Canada Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
Point Géodesique no. 2378, Terres et Forêts Québec (cropped).jpg, Benchmark disk in
Ottawa Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the core ...
, Ontario, Canada Image:Barcdock1.jpg, Vial Moll de Bosch i Alsina, near Port de Barcelona building, & pedestrian crossing
Barcelona Barcelona ( , , ) is a city on the coast of northeastern Spain. It is the capital and largest city of the autonomous community of Catalonia, as well as the second most populous municipality of Spain. With a population of 1.6 million within ci ...
File:Charing Cross benchmark.jpg, Benchmark on the plinth of the statue of King Charles I in
Trafalgar Square Trafalgar Square ( ) is a public square in the City of Westminster, Central London, laid out in the early 19th century around the area formerly known as Charing Cross. At its centre is a high column bearing a statue of Admiral Nelson commemo ...
, London: the site of the medieval
Charing Cross Charing Cross ( ) is a junction in Westminster, London, England, where six routes meet. Clockwise from north these are: the east side of Trafalgar Square leading to St Martin's Place and then Charing Cross Road; the Strand leading to the City; ...
, and the point from which distances from London are calculated File:PylonBenchmarkNMKT.jpg, Benchmark painted on an electricity pylon's foundation File:Dorfkirche Flemsdorf 2020 Vermessungspunkt.jpg, Benchmark of the Prussian Survey Authority on a church in Brandenburg


See also

*
Benchmarking Benchmarking is the practice of comparing business processes and performance metrics to industry bests and best practices from other companies. Dimensions typically measured are quality, time and cost. Benchmarking is used to measure performan ...
—a recreational activity in which participants search for benchmarks using a handheld
GPS The Global Positioning System (GPS), originally Navstar GPS, is a Radionavigation-satellite service, satellite-based radionavigation system owned by the United States government and operated by the United States Space Force. It is one of t ...
receiver. *
Broad arrow A broad arrow, of which a pheon is a variant, is a stylised representation of a metal arrowhead, comprising a tang and two barbs meeting at a point. It is a symbol used traditionally in heraldry, most notably in England, and later by the Britis ...
*
Geoid The geoid () is the shape that the ocean surface would take under the influence of the gravity of Earth, including gravitational attraction and Earth's rotation, if other influences such as winds and tides were absent. This surface is extended ...
*
Levelling Levelling or leveling (American English; American and British English spelling differences#Doubled in British English, see spelling differences) is a branch of surveying, the object of which is to establish or verify or measure the height of sp ...
—a surveying technique that uses benchmarks *
Ordnance datum In the British Isles, an ordnance datum or OD is a vertical datum used by an ordnance survey as the basis for deriving altitudes on maps. A spot height may be expressed as AOD for "above ordnance datum". Usually mean sea level (MSL) is used fo ...
*
Spot height A spot height is an exact point on a map with an elevation recorded beside it that represents its height above a given datum.Whittow, John (1984). ''Dictionary of Physical Geography''. London: Penguin, 1984, p. 506. . In the UK this is the Ordna ...


References


External links

{{EB1911 poster, Bench-mark
Canadian Spatial Reference System

History of the Canadian Geodetic Survey Division

UK benchmark database

Detailed description of the different types of UK benchmark

US NGS Benchmarks overlaid on a Google Map

Benchmarks and levelling points

Benchmarks in the UK, mostly Gloucestershire, plus Gibraltar & Barcelona
Surveying and geodesy markers Vertical position