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geodesy iconGeodesy Roadmap to Resources


The National Geodetic Survey (NGS) develops and maintains a national system of positioning data needed for transportation, navigation, and communication systems. NGS also implements a coastal mapping program, conducts aerial photography surveys, develops standards for conducting geodetic surveys and assists state, county, and municipal agencies throughout the United States with training workshops.

The Web pages listed below are a small selection of the information and technical resources provided by NGS and similar organizations around the world. Many more resources are accessible through the NGS Web site

In addition, some of the Web pages listed reside within larger Web sites. You may wish to browse through these Web sites and examine other available resources.

The National Geodetic Survey - What it Does

NGS: Positioning America For the Future

This Web page provides a brief overview of the National Geodetic Survey (NGS). On the right hand side of the page are links where you can download short descriptions of many NGS programs (PDF format) including the Ionosphere Mapping Program, the Height Modernization Program and the National CORS Program. If you scroll to the bottom of this page, under the heading "So, What is Geodesy? Who Needs it and Why?" there are links to excellent materials (PDF format) explaining the role of geodesy in contemporary America, and two very good on-line geodesy tutorials.

NOS Web Site News Feature on NGS Activities

This Web page briefly describes the National Spatial Reference System (NSRS), the Global Positioning System (GPS), and the NGS Height Modernization program. The page discusses the importance of geodesy and provides links to related geodetic programs and downloadable information.

The History of the National Geodetic Survey

This Web site provides a wealth of information on the history of the National Geodetic Survey and its evolution from the Survey of the Coast, the United States first civilian scientific agency, formed by Thomas Jefferson in 1807. In addition to over 600 pages of reader-friendly text, there are links to historical photo albums, short stories about geodetic expeditions, as well as historical maps and charts. A must see !

The National Geodetic Survey's Continuously Operating Reference Station (CORS) Web Site.

This is the official Web site of NGS's continuously operating reference stations (CORS). Surveyors, geographic information system (GIS) professionals, engineers, scientists, and others use data from the CORS system to assure horizontal and vertical positioning accuracies within a few centimeters.

A central feature of this Web site is a "dynamic" map of the United States and its territories. The different symbols and colors on the map indicate the locations and sampling rates of hundreds of CORS stations in the United States' network. By selecting and "clicking" on an area of the map you can "zoom" into a region where a CORS receiver is located. By selecting and "clicking" on a specific receiver, you can view a detailed area map showing the receiver's exact location, see photographs of the receiver, and view coordinate data that the receiver is collecting from Global Positioning System satellites in real time.

When a specific receiver has been selected, you can obtain different kinds of information about it from the menu on the left hand side of the Web page. Just select the information you would like to see and then "click" the submit button.

Ecosystem Health and Land Loss in the Chesapeake Bay

Although this Web site dates back to 1997, it demonstrates how geodetic and other monitoring techniques can be used together to determine the health of the Chesapeake Bay ecosystem. The project description includes sections on sea level variation, land subsidence, remote sensing of coastlines using satellites and GPS. Each section of the project is accompanied by enhancing graphics and images.

The Geoid

This Web page links to definitions, descriptions and research about the geoid. The link to "What is the Geoid" is geared to the general public and is accompanied by several good images. While most links on the page present information better suited to individuals with specific training in the geodetic sciences, there are many excellent images and kernels of information sprinkled throughout this pages links.

The Canadian Geodetic Survey Division - What is Geodesy?

This tutorial is offered by the Geodetic Survey Division of Canada and includes information on geodesy, GPS, the geoid, surveying, and gravity. The tutorial is accompanied by well-developed graphics. You can select these and other subjects by "clicking" on them from the menu of topics on the left hand side of the Web page.

Links to Additional Resources

This portal Web site offers links to many geodetic resources including government agencies, university programs, scientific organizations, and international institutes. Many of these organizations offerings are very technical in nature however, there are hidden gems to be found within the list of links; for example, were you aware that the United States Department of Defense has a directorate of time ? Check out: and other links here.


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