What is air gap?

The NOAA Air Gap system is a tool that measures the clearance between the water surface and the bridge.

By a margin of 2.1 feet, the USS New York clears the Huey P. Long Bridge on June 27, 2009. | Download

Air gap measurements are updated every six minutes to account for changes in water level and bridge height, due to bridge traffic, air temperature, and other factors. Data on air gap along with real-time data on water conditions like tides, currents, and winds, help ship captains safely enter and leave U.S. ports. This information is critical for a ship captain to safely navigate a ship under a bridge.

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