An official website of the United States government.
Here's how you know we're official.
A .gov website belongs to an official government organization in the United States.
A small lock or https:// means you’ve safely connected to a .gov website. Share sensitive information only on official, secure websites.
VIDEO: Watch how geodesy plays a key role in so many aspects of modern life and how this science helps you get from point A to B. Transcript
Many organizations use geodesy to map the U.S. shoreline, determine land boundaries, and improve transportation and navigation safety. To measure points on the Earth’s surface, geodesists assign coordinates (similar to a unique address) to points all over the Earth. In the past, geodesists determined the coordinates of points by using Earth-based surveying tools to measure the distances between points. Today, geodesists use space-based tools like the Global Positioning System (GPS) to measure points on the Earth’s surface.
Geodesists must accurately define the coordinates of points on the surface of the Earth in a consistent manner. A set of accurately measured points is the basis for the National Spatial Reference System, which allows different kinds of maps to be consistent with one another.
To measure the Earth, geodesists build simple mathematical models of the Earth which capture the largest, most obvious features. Geodesists have adopted the ellipsoid as the most basic model of the Earth. Because the ellipsoid is based on a very simple mathematical model, it can be completely smooth and does not include any mountains or valleys. When additional detail of the Earth is needed, geodesists use the geoid. A geoid has a shape very similar to global mean sea level, but this exists over the whole globe, not just over the oceans.
Every day,we need to know where we are and how to get where we need to go. But did you ever stop to think just how we know where “here” is, and how the technology we rely on gets us “there”?
It's all thanks to geodesy:the science of measuring where things are on Earth and how those locations change over time. It starts with reference points—physical markers placed in the ground all over the U.S. There are over a million of them! And NOAA keeps track of them all. You’ve probably walked by one without noticing. In the past, surveyors would leapfrog across the entire country, measuring the exact location of each marker. Now, many of those markers are automated, continuously receiving signals from GPS satellites to compute their precise locations. By knowing where all those markers are, GPS tells us precisely where we are and how to get where we need to go. But it's not that simple. Earth itself is always changing—from shifting tectonic plates to sinking land to changing water levels and tides. So, NOAA's geodesists are always measuring. Part scientists, part engineers, and part detectives, geodesists study the shape and movement of the Earth and measure positions with great precision. Look around you. So many things in our modern world are made possible by geodesy. And the system is always improving, with geodesists being able to measure even more of Earth's changes and with more precision than ever before. And that's more important now than ever ...
Trying to navigate a busy street on your way to the grocery store? Geodesy helps you get there quickly and safely. That farmer trying to grow as much food as they can? They're using geodesy to save water and fertilizer, applying them to crops exactly where needed. That means a more resilient and reliable food supply at your local grocery store. That package you ordered online? It likely passed under bridges with only feet to spare.
NOAA's systems work together—measuring tides and bridge clearance, all tied to a common reference—so ships can carry more cargo and travel safely through port. Worried about flooding where you live? Geodesists measure slight differences in Earth's gravity to better understand the shape of the planet. This information helps support more accurate flood maps to keep you and your community safe. Lost or injured on a hike? Geodesy helps responders coordinate faster to reach you in an emergency.
Geodesy: It's the invisible utility that supports and connects everything around you. And homes, buildings, even entire cities ... They exist, thanks to the work of geodesists. Because modern life depends on knowing exactly where “here” is.
Social