The National Geodetic Survey (NGS) develops and maintains a national coordinate system, which provides the foundation for transportation, navigation, land record systems, mapping and charting efforts, defense operations, and a multitude of scientific and engineering applications. NGS products, services, and data support maritime navigation, aviation safety, hurricane evacuation routes, climate change activities, ocean observing, and more.
A geoid model is a complex mathematical representation of global mean sea level with many practical applications for surveyors, engineers, and the scientific community.
In 2012, the National Geodetic Survey released GEOID12A, the latest model of the geoid, which can be described as the "shape" of mean sea level around the globe. Surveyors, engineers, and the scientific community use the geoid (pronounced jee-oid)—a model derived through complex math and gravity measurements—to measure surface elevations with a high degree of accuracy.
While the science behind the construction of geoid models is very complex, one reason why we need such models is surprisingly simple: a small difference in height measurement on land determines which way water flows, and this makes the development of new and better geoid models an ongoing priority.
By providing a more accurate means of determining elevations, the new model will assist those involved in floodplain management, coastal and emergency response, port operations, and river flow monitoring. More accurate elevations also help lessen risks to coastal communities caused by hurricanes, storm surges, tsunamis, and other flood-related events. Engineering and other activities requiring accurate elevations also benefit, including precision agriculture and the construction and maintenance of dams, levees, roads, and other infrastructure.
Surveyors work to improve the National Spatial Reference System, which is essential for many activities that require highly accurate location and elevation data like property surveys, utilities, and siting public infrastructure such as bridges to ensure safe navigation.
The National Geodetic Survey (NGS) defines and manages the National Spatial Reference System—the coordinate system that defines latitude, longitude, height, scale, gravity, orientation, and shoreline throughout the United States. The first major improvement to this reference system, NGS’s National Adjustment of 2011 Project, integrated new position information for more than 80,000 survey marks with NGS's more advanced Global Positioning System receiver-based control points. As a result, the coordinates of the nation's reference system are now consistent across space and time.
Consistency in the National Spatial Reference System is critical, because people rely on positioning data for countless engineering and scientific applications—to plan roads to improve traffic flow, to check the integrity of buildings, to ensure airplanes land safely on the runway, and even to measure small changes in sea level over time. Surveyors and others use the reference system throughout the country to ensure their positional coordinates are compatible with those determined by others, so that when experts create maps; mark off property boundaries; and plan, design, and build roads, bridges, and other structures, everything matches up.
NOAA collects aerial imagery used to improve the accuracy of shoreline data.
For every dollar American taxpayers spend on the National Geodetic Survey’s Coastal Mapping Program, they receive more than $35 in benefits. This statistic was the result of a recent independent socio-economic scoping study.
The program provides critical baseline data to accurately map the U.S. shoreline. These data are important for national security, maritime shipping, and navigation. The program also provides geographical reference data needed to manage, develop, conserve, and protect coastal resources.
Direct economic benefits of the program alone were estimated at $100 million—15 times program costs. Also, the study estimated that the Coastal Mapping Program supports 1,500 jobs outside of the program.
NOAA derives shoreline data through various remote sensing technologies including aerial imagery, satellite imagery, and Light Detection and Ranging (LiDAR).
The National Geodetic Survey conducted an elevation survey of the Washington Monument and the National Mall. Results indicate the monument experienced no significant vertical movement as a result of a 2011 earthquake in the region.
A survey conducted earlier this year by NOAA’s National Geodetic Survey (NGS) indicates that a rare 5.8-magnitude earthquake in the region in August 2011 had no discernible impact on the settlement of the Washington Monument.
The 2012 survey also showed—based on five leveling surveys of relatively consistent points of measurement taken since 1926—that the area of the National Mall built on landfill has settled at a rate of approximately 0.013 inches per year, or a total of approximately one inch. This region includes the Washington Monument and areas south to the Potomac River.
NGS further found that the rate of settlement for the Washington Monument itself, based on multiple measurements taken since 1901, is 0.02 inches per year. This indicates that the monument has settled approximately 2.2 inches since 1901.
The 2012 survey, which encompassed the entire National Mall in Washington, D.C., is the first of what NOAA and the National Park Service plan to be a series of periodic geodetic leveling observations of the Mall area to better track subsidence changes and ensure adequate preservation of the Mall. The 2012 survey was conducted at the request of the National Park Service.
In 2012, the National Geodetic Survey (NGS) released the Leveling Online Computations User Service (LOCUS) Web utility— software that performs a preliminary adjustment of geodetic leveling, enabling surveyors to obtain accurate heights referenced to the official National Vertical Datum in their project area. An additional benefit of the new software is that LOCUS-based leveling projects submitted to NGS for publication will require less processing prior to publication. Accurate heights are necessary for floodplain mapping, coastal zone management, monitoring sea-level change, safe navigation, and many other mapping and engineering applications.