Reaching New Heights

NOAA scientists are transforming how to measure accurate heights and how we can understand the water flows beyond the ground.

Errors and inaccuracy in measuring heights from the foundation could lead a big difference between a flooded home and a safe dry home.

Did you know that buying a property near a river that routinely floods require flood insurance? One important step to obtain a flood insurance is to have access to the certified elevation of the property from a professional surveyor and/or applications.

Critical data in a low-lying coastal areas are hard to gain access simply because professionals need to have knowledge on how water will flow from point to point across the ground. Height specialists who examine the elevations of properties create flood zone maps, plot hurricane evacuation routes, and plan future coastal development to account for sea level rise all depend on the accuracy of measuring heights.

Vertical Datum

Measuring heights meet NOAA’s National Geodetic Survey (NGS). National Geodetic Survey provides the substructure for all positioning activities in the nation. Scientists at NGS preserve a national coordinate system that defines the foundational elements of latitude, longitude, elevation, orientation, and shoreline data throughout the US. This system ensures that those who utilize the accurate positioning data are using the same heights reference. The height element of this nationwide system is called the vertical datum. It is a collection of particular points on the Earth with known heights either above or below the sea level.

Uneven Sea Level

Measuring elevation from sea level is not as easy as it might seem. Sea level is uneven and irregular. All the large and small variations to the size, shape, and mass distribution of the earth cause variations in different places. These variations regulates the shape of the planet’s water and it is what we call global sea level.

Reaching New Heights

Calculation of accurate heights based on mean sea level can be tricky, time-consuming and can also cost a lot. Scientists at NGS are putting their hard work and efforts to make accurate height measurement better than it is today. The result will be a new vertical datum, slated to be released in 2022 that will allow those that need to calculate heights to within about an inch for most locations around the nation.

The new vertical datum will serve as the starting point to update height data over time as gravity values around the nation shift with the changing landscape of the Earth. It will be straightforward to get accurate height information because it will also be tied into GPS. And lastly, users will be able to easily determine how heights are changing over time for a certain location. This new model will be a huge improvement when monitoring things like levee heights, hurricane evacuation routes, or even the elevation of your property.

The Gravity for the Redefinition of the American Vertical Datum will contribute about $4.8 billion in social and economic benefits to the nation over 15 years through improved floodplain mapping, coastal resource management, construction, agriculture, and emergency evacuation planning. A recent study also calculates a savings of $2.2 billion in improved floodplain management alone, because the new and improved height measurements will result in fewer property damage from flooding circumstances.

Surveying the entire gravity field of the US to update the nation’s vertical datum might be one of the most ambitious projects ever managed in the more than 150 year history of the NGS but this will definitely improve how we measure accurate heights from this day to the future.