What are NAVD88 and GEOID18?

The North American Vertical Datum of 1988 NAVD88) and GEOID18, are two vertical datums used for elevations in North America.

NAVD88, or the North American Vertical Datum of 1988, is a vertical datum used for elevations in North America. It was established by the National Geodetic Survey (NGS) of the United States government as the official vertical datum for the United States, Canada, and Mexico.

A vertical datum is a reference surface used to measure elevations or depths. In the case of NAVD88, it is a reference surface used to measure elevations above sea level. The NGS established the datum by averaging the mean sea level at over 200 tide stations along the coast of North America. It is based on a network of over 600 benchmarks (fixed points with known elevation) and is the foundation of the U.S National Spatial Reference System (NSRS).

NAVD88 & Surveying

In the field of surveying, NAVD88 is a crucial reference surface. It is used to determine the elevation of points on the earth's surface, which is essential for mapping, land surveying, and construction projects. For example, a surveyor may use NAVD88 to determine the elevation of a building's foundation, or to establish a benchmark for a construction project. Additionally, it serves as a common reference for the control and mapping data that enables the vertical integration of data from different sources.

One of the main advantages of NAVD88 is its wide acceptance and use in North America. It is used by government agencies, private companies, and individuals, making it easy for surveyors and engineers to obtain accurate elevations for points on the earth's surface. It also ensures consistency in elevations across different regions, making comparing data from different locations easier.

The Next Chapter: GEOID18

In recent years, the NGS has released a new version of the vertical datum, the Geoid Height (GEOID18), which is the latest version of the vertical reference surface that provides a more accurate representation of the earth's gravity field and it's used to improve the precision of the elevations from NAVD88. This is especially important for areas with significant elevation changes.

NAVD88 provides a common reference for the control and mapping data, making it easier for surveyors and engineers to obtain accurate elevations for points on the earth's surface. With the advancement in technology, a new version of the vertical datum, the Geoid Height (GEOID18) has been released to improve the precision of the elevations from NAVD88.