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{{Organization
|OrganizationName=U.S. National Geodetic Survey
|OrganizationType=Government Agency
|Mission=To define, maintain, and provide access to the National Spatial Reference System to ensure consistent coordinates for positioning, height, and gravity across the United States.
|ParentOrganization=National Oceanic and Atmospheric Administration (NOAA), under the National Ocean Service
|CreationLegislation=Originally part of the Survey of the Coast established by an act of Congress in 1807, became NGS under NOAA in 1970 with the National Oceanic and Atmospheric Administration Organic Act
|Employees=200
|Budget=Integrated into NOAA's budget; specifics not publicly itemized (as of last known data)
|OrganizationExecutive=Director (National Geodetic Survey)
|Services=* Maintenance of the National Spatial Reference System (NSRS)
* Online Positioning User Service (OPUS) for GPS data processing
* Geodetic control and survey mark data management
* Development and distribution of geodetic models like the geoid and gravity models
* Support for mapping, charting, and navigation
|Regulations=* No direct regulatory authority, but supports compliance with various laws by providing geodetic infrastructure, e.g., for Federal Aviation Administration (FAA) navigational requirements
|HeadquartersLocation=38.99254, -77.03066
|HeadquartersAddress=1315 East-West Highway, Silver Spring, MD 20910
|Website=https://geodesy.noaa.gov/
}}
{{Short description|U.S. federal surveying and mapping agency}}
{{Distinguish|United States Coast and Geodetic Survey|United States Geological Survey}}

The '''National Geodetic Survey''' ('''NGS''') is a [[List of federal agencies in the United States|United States federal agency]] based in [[Washington, D.C.]] that defines and manages a national [[geographic coordinate system|coordinate system]], providing the foundation for transportation and communication, mapping and charting, and a large number of science and engineering applications. Since its founding in 1970, it has been part of the [[National Oceanic and Atmospheric Administration]] (NOAA), a division within the [[United States Department of Commerce|Department of Commerce]].

[[File:DarienCTUSCoastAndGeodeticSurvey1965Marker11042007.jpg|thumb|upright=1|Closeup of a United States Coast and Geodetic Survey marker embedded in a large rock in front of the Noroton Volunteer Fire Department in [[Darien, Connecticut|Darien]], [[Connecticut]]]]
[[File:Geodeticsurveypicwickenburg.jpg|thumb|upright=1|A survey marker in [[Wickenburg, Arizona|Wickenburg]], [[Arizona]]]]
[[File:East_Falls_Church_Station_survey_marker.jpg|thumb|upright=1|A metro survey marker at [[East Falls Church station]] in [[Arlington County, Virginia|Arlington County]], [[Virginia]]]]

==History==
{{see|United States Coast and Geodetic Survey#History}}

The National Geodetic Survey's history and heritage are intertwined with those of other NOAA offices. It traces its history to the [[Survey of the Coast]], which was formed in 1807 as the first scientific agency of the [[Federal government of the United States|U.S. federal government]]. It became the United States Coast Survey in 1836 and the United States Coast and Geodetic Survey in 1878, the latter name change reflecting the increasing role of [[geodesy]] in its work. Upon the creation of NOAA in 1970, the Coast and Geodetic Survey was abolished and its responsibilities were split among various agencies and offices of NOAA. The Coast and Geodetic Survey′s former geodetic responsibilities were placed under the new National Geodetic Survey in NOAA's National Ocean Survey (later renamed the [[National Ocean Service]]).

In 2009, former [[NOAA Commissioned Officer Corps]] officer [[Juliana P. Blackwell]] was named NGS Director, becoming the first woman to head either NGS or any of its ancestor organizations.

==Purpose and function==
The National Geodetic Survey is an office of NOAA's [[National Ocean Service]]. Its core function is to maintain the [[National Spatial Reference System]] (NSRS), "a consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation throughout the United States".<ref name="What_We_Do">{{cite web |url=http://geodesy.noaa.gov/INFO/WhatWeDo.shtml |work=National Geodetic Survey Website |access-date=May 27, 2013 |title=National Geodetic Survey – What We Do}}</ref> NGS is responsible for defining the NSRS and its relationship with the [[International Terrestrial Reference System and Frame|International Terrestrial Reference Frame]] (ITRF). The NSRS enables precise and accessible knowledge of where things are in the United States and its territories.

The NSRS may be divided into its geometric and physical components. The official [[geodetic datum]] of the United States, [[North American Datum|NAD83]] defines the geometric relationship between points within the United States in three-dimensional space. The datum may be accessed via NGS's network of survey marks or through the [[Real-time kinematic|Continuously Operating Reference Station]] (CORS) network of [[Global Positioning System|GPS]] reference antennas. NGS is responsible for computing the relationship between NAD83 and the ITRF. The physical components of the NSRS are reflected in its height system, defined by the vertical datum [[North American Vertical Datum of 1988|NAVD88]]. This datum is a network of [[orthometric height]]s obtained through spirit [[Levelling|leveling]]. Because of the close relationship between height and Earth's gravity field, NGS also collects and curates terrestrial [[gravity]] measurements and develops regional models of the [[geoid]] (the level surface that best approximates sea level) and its slope, the [[Vertical deflection|deflection of the vertical]]. NGS is responsible for ensuring the accuracy of the NSRS over time, even as the [[North American Plate|North American plate]] rotates and deforms over time due to crustal strain, [[post-glacial rebound]], [[subsidence]], elastic deformation of the crust, and other geophysical phenomena.

NGS will release new datums in 2022.<ref>{{cite web |title=New Datums |url=https://geodesy.noaa.gov/datums/newdatums/index.shtml |website=National Geodetic Survey |access-date=March 21, 2017}}</ref> The North American Terrestrial Reference Frame of 2022 (NATRF2022) will supersede NAD83 in defining the geometric relationship between the North American plate and the ITRF.<ref name="geodesy.noaa.gov">{{cite web |author=US Department of Commerce, NOAA, National Geodetic Survey |title=Naming Conventions, New Datums |url=https://geodesy.noaa.gov/datums/newdatums/naming-convention.shtml |website=geodesy.noaa.gov |language=EN-US}}</ref> United States territories on the Pacific, Caribbean, and Mariana plates will have their own respective geodetic datums. The North American-Pacific Geopotential Datum of 2022 (NAPGD2022) will separately define the height system of the United States and its territories, replacing NAVD88.<ref name="geodesy.noaa.gov"/> It will use a geoid model accurate to 1 centimeter (0.4") to relate orthometric height to ellipsoidal height measured by GPS, eliminating the need for future leveling projects. This geoid model will be based on airborne and terrestrial gravity measurements collected by NGS's GRAV-D program as well as satellite-based gravity models derived from observations collected by [[GRACE and GRACE-FO|GRACE]], [[GOCE]], and [[Satellite geodesy|satellite altimetry]] missions.<ref>{{cite web |author=US Department of Commerce, NOAA, National Geodetic Survey |title=xGEOID16 Evaluation Computation |url=https://beta.ngs.noaa.gov/GEOID/xGEOID16/ |website=beta.ngs.noaa.gov |language=EN-US}}</ref>

NGS provides a number of other public services.<ref name="What_We_Do"/> It maps changing shorelines in the United States and provides aerial imagery of regions affected by natural disasters, enabling rapid damage assessment by emergency managers and members of the public. The Online Positioning and User Service (OPUS) processes user-input GPS data and outputs position solutions within the NSRS. The agency offers other tools for conversion between datums.

==See also==
* [[Height Modernization]]
* [[Surveying]]
* [[Topography]]

==References==
{{reflist|2}}

==External links==
* {{oweb|https://geodesy.noaa.gov/}}

{{ES_Government|state=collapsed}}

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[[Category:Exploration of North America]]
[[Category:Geodesy organizations]]
[[Category:Geographic data and information organizations in the United States]]
[[Category:Government agencies established in 1970]]
[[Category:National Oceanic and Atmospheric Administration|National Geodetic Survey]]