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National Geodetic Survey is the name I see thrown out the most when people talk about benchmarks. But many of the actual benchmarks I have seen are stamped with "U.S. Geological Survey". These are different organizations - NGS is under NOAA which is under the Dept of Commerce, whereas USGS is part of Dept of the Interior. Anyone know why the difference? Did USGS do benchmarks back in the day then pass it to NGS, or am I totally off? Or does this even matter? I'm just curious.

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Well this is part of it that I know.

1-1. Surveying.Surveying has to do with determination of the relative location of points on or near the surface of the Earth.The Art of measuring horizontal and vertical distances between objects,of measuring angles between lines.............

Thus the process of surveying is divided into the Fieldwork taking measurements and the Officework of computing and drawing neccesary to the purpose of the Survey.

1-2. Uses of Surveys

The earliest Surveys known were for the purpose of establishing the boundries of the Land,and such Surveys are still the important work of many surveyors.(BLM, Dept. of Interior)

For many years the Government,and in some instances the individual states,have conducted surveys over large areas for a variety of purposes.(USGS)and (States)

The Principal work so far accomplished consists of the fixing of National and State Boundries,the charting of coast lines and Navigable lakes and streams (USCGS)and(Army Corps of Engineers).

Thus Surveys are divided into 3 Classes:

1.Those for the primary purpose of establishing the boundries of Land.

2.Those providing information necessary for the purpose of construction of public or private works.

3. Those of large extent and high precision conducted by the Government and to some extent the States.


There is no hard and fast lineof demarcation between surveys of one class and those of another class and those of another as regards the methods employed,results obtained,or use of the data of the survey.


1-3 The Earth as a Spheroid

The Earth is an oblate spheroid of revolution,the length of its polar axis being somewhat less than that of its equitorial axis.

The lengths of these are variously computed as follows:

Clark (1866)....

Polar axis,ft.=41,710,242

Equitorial axis ft.=41,852,124


Hayford (1909)

Polar axis ft.=41,711,920

Equtorial axis ft.=41,852,860


Adopted (1924)

by International Geodetic and Geophysical Union

Polar axis ft.=41,711,940*

Equtorial axis ft.=41,852,860


*Computed from Equtorial axis by assuming that the flattening of the Earth is exactly

1/297, 1 divded by 297.

The lengths determined by Clark have been generaly accepted in the United States and have been used in Govermental Land Surveys.

HAYFORD'S values are regarded as being more nearly correct than those of Clark.


The values adopted by the International Geodetic and Geophysical Union are published by the U.S. Naval Observatory.


Surveying Agencies


1.U.S.Geological Survey

Est. 1879 is in charge of preparing the National Topographic Map seriescovering the United States and it's outlying areas.


2. U.S. Coast and Geodetic Survey

This Bureau of the Enviromental Services Administration,ESSA,Est. 1807,celebrates its 196 Anniversary.It publishes Nautical charts of the Coastal Waters of the U.S. and it's Territorial possessions,executes the principal geodetic surveys of the country,and prepares and distributes the aeronautical charts needed by American civil aviation.

President Thomas Jefferson and Ferdinand Hassler,noted Swiss Scientist,were the Founders of the Coast Survey.


3. U.S. Naval Oceanographic Office.

this agency performs essentially the same hydrographic charting functions as the Coast Survey but with respect to waters not contiguous to the U.S or possessions.


4. U.S. Lake Survey.

This is the nautical charting agency of the Corps of Engineers. It is concerned with publications of navigation charts for the Great Lakes.


5. U.S. Bureau of Land Management

Responsible for the Surveys of the Publis Domain.Rectangular public surveys are still being executed in some of the Western States and Alaska.


6. U.S. Corps of Engineers(U.S. Army)

Each Army engineer district office has a survey section that performs many kinds of surveying tasks associated with the control of Navigable water over which the corps has jurisdiction.


7.U.S. Bureau of Reclamation

The extensive construction program of this org. involves many survey tasks ranging from the preliminary mapping of proposed resivoir to the layout of a large dam.












Arkansas Missouri Geocachers Association


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It can be confusing as to the responsibilities of the various agencies. As noted NGS is part of the National Oceanic and Atmospheric Administration in the Department of Commerce. The U.S. Geological Survey (USGS) is in the Department of the Interior. NGS traces it’s legacy to the Organic Act signed by President Jefferson on February 10, 1807 creating the Survey of the Coast. Later changed in name to Coast Survey (1836), then Coast and Geodetic Survey in 1878, and finally in 1970 to NGS. NGS has the responsibility for the definition and maintenance of the national horizontal and vertical datums used by the various other agencies to define national mapping (USGS), coastal charting (NOAA/Office of Coast Survey), and Aeronautical Charting (FAA), as well has a host of other applications. The monuments established by NGS and predecessor agencies forms the framework from which the other agencies will establish lower accuracy control for their individual applications. USGS would often establish more monuments in various areas to support the needs for mapping. These marks however, were typically of a lower order of accuracy than NGS would establish. The same is true with the other agencies. Only NGS maintains a nation-wide digital data base of control. For more than 70 years NGS has welcomed the addition of data from many different sources into the national framework as long as that data meets the high level of integrity necessary for a national reference system. NGS is the only such agency in the world that will accept survey data from literally anyone as long as it meets the specific requirements for accuracy, monument stability and submitted in the appropriate computer format. You do not have to be a Federal or State surveying agency or hold any specific license such as a professional land surveyor or professional engineer to submit data to NGS. NGS established the foundational data and establishes standards for surveys to meet the many Federal, State and local requirements.


Many people, even surveyors who should know better often confuse the functions of NGS and USGS. With a few notable exceptions USGS is pretty much out of the control survey business.


It should be noted that the U.S. Lake Survey mentioned by GEO*Trailblazer 1 was disbanded about 15 years ago and it’s duties divided between the NGS, Corps of Engineers and the NOAA/Center for Operational Oceanographic Products and Services (CO-OPS).

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Interesting. Thanks for the info. And confusing it is indeed. Also a bit tricky to find some of them. Going tomorrow or Tuesday to a BM deep in the woods that has no recovery in the database since 1947.

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