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Diving Deeper: What is Geodesy? (audio podcast)

Explore: Aerial Photography and Shoreline Mapping

Explore: Global Positioning

Explore: Height Modernization

NOS Education: Geodesy Tutorial

National Geodetic Survey

Employees of NGS conduct leveling to investigate possible subsidence (land sinking) of the Washington Monument for the National Park Service.

While we may tend to think of the Earth as a uniform, smooth globe, in reality its shape and surface are quite complex. This complexity provides challenges when trying to determine the latitude, longitude, or elevation of a point on the Earth’s surface. Figuring all this out is part of the science of geodesy.

At the National Ocean Service, geodesy is the business of the National Geodetic Survey (NGS). NGS develops and maintains the National Spatial Reference System, a national coordinate system that provides the foundation for transportation, navigation, land record systems, mapping and charting efforts, and a multitude of scientific and engineering applications. This system defines position (latitude, longitude, and elevation), distances and directions between points, strength and direction of gravity (no, it is not simply “straight down”), and how these change over time.

NGS implements a coastal mapping program to define the national shoreline and other features needed for updating nautical charts and managing our coastal resources. After natural disasters, NGS conducts aerial photography surveys to help in search and rescue efforts and speed recovery. Additionally, NGS provides airport geodetic control, runway, navigational aid, obstruction, and other aeronautical data critical to the operation of the National Airspace System.

Additionally, NGS develops industry guidelines, specifications, and standards and provides training for conducting geodetic surveys and using surveying equipment.

NGS products, services, and data support maritime navigation, aviation safety, hurricane evacuation routes, coastal resiliency and restoration, monitoring climate change impacts, ocean observing, and more.