U.S. National Geodetic Survey facts for kids
The National Geodetic Survey (NGS) is a special government group in the United States. It helps us know exactly where things are across the country. Think of it like creating a super-accurate map for everyone to use! This helps with things like building roads, sending signals, and making detailed maps. NGS started in 1970 and is part of NOAA, which is a science agency within the United States Department of Commerce.
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How NGS Started: A Brief History
The National Geodetic Survey has a long and interesting past. Its roots go back to 1807, when a group called the Survey of the Coast was formed. This was the very first science agency of the U.S. government.
Over the years, its name changed. In 1836, it became the United States Coast Survey. Then, in 1878, it was renamed the United States Coast and Geodetic Survey. This new name showed that the group was doing more work with geodesy. Geodesy is the science of measuring Earth's shape, gravity, and how points on its surface change over time.
When NOAA was created in 1970, the old Coast and Geodetic Survey was split up. Its job of measuring Earth's shape and positions went to the new National Geodetic Survey. This new NGS became part of NOAA's National Ocean Survey, which is now called the National Ocean Service.
In 2009, Juliana P. Blackwell became the Director of the National Geodetic Survey. She was the first woman to lead NGS or any of its earlier groups.
What Does NGS Do?
The main job of the National Geodetic Survey is to keep up the National Spatial Reference System (NSRS). This is like a super-accurate grid for the entire United States. It defines things like how far north or south you are (latitude) and how far east or west you are (longitude). It also tells you your height, how big things are, and even how gravity works in different places.
NGS makes sure this system is correct for the U.S. and its territories. It also connects the NSRS to a worldwide system called the International Terrestrial Reference Frame. This helps everyone around the world use the same measurements.
Mapping Our World: How the NSRS Works
The NSRS has two main parts: geometric and physical.
Geometric Measurements: Finding Your Spot
The geometric part helps us find exact locations in 3D space. The official system for this in the U.S. is called NAD83. You can use this system through special survey markers that NGS places on the ground. You can also use the Continuously Operating Reference Station (CORS) network. This network uses many GPS antennas that are always on. NGS also figures out how NAD83 connects to the international system.
Physical Measurements: Understanding Height and Gravity
The physical part of the NSRS deals with height. The main height system is called NAVD88. This system uses measurements taken by "leveling," which is a way to find the exact height difference between two points.
Because height is linked to Earth's gravity, NGS also collects gravity measurements. They create maps of the geoid, which is like the true sea level surface of the Earth. This helps them understand how gravity affects height measurements.
NGS works to keep the NSRS accurate over time. The North American plate (the part of Earth's crust we live on) is always moving and changing. Things like melting glaciers, sinking land, and other natural events can change the ground. NGS makes sure their measurements stay correct even with these changes.
New Datums Coming Soon!
NGS is planning to release new measurement systems in 2022.
- The North American Terrestrial Reference Frame of 2022 (NATRF2022) will replace NAD83. It will help define how the North American plate relates to the international system. Other U.S. territories will have their own special systems.
- The North American-Pacific Geopotential Datum of 2022 (NAPGD2022) will replace NAVD88 for heights. This new system will use a very accurate geoid model. This model will be so precise that it will make it easier to figure out heights using GPS, without needing as many leveling projects. This geoid model uses gravity measurements collected by NGS's GRAV-D program. It also uses information from satellites like GRACE and GOCE.
Other Helpful Services from NGS
NGS offers many other services to the public:
- They map how coastlines change in the U.S.
- They provide aerial pictures of areas hit by natural disasters. This helps emergency workers and people quickly see the damage.
- Their Online Positioning and User Service (OPUS) helps people use their own GPS data. It gives them accurate location information within the NSRS.
- NGS also has tools to help people convert data between different measurement systems.
See also
- Height Modernization
- Surveying
- Topography
