Ocean Systems Test and Evaluation Program : Microwave Air Gap - Bridge Clearance Sensor Test, Evaluation and Implementation Report.

Abstract

The National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) manages several programs to monitor the Nation's coastal waters, including PORTS® (Physical Oceanographic Real-Time System). PORTS® provides ship masters and pilots with accurate, real-time information to help avoid groundings and collisions. CO-OPS requires an expanding suite of instruments to provide critical data from bays and harbors to support the maritime community. Many harbors are depth-constrained, and many bridge heights also limit safe vessel passage. With increasing vessel size and vessel traffic, there is a continually increasing risk of overhead allision with bridges. Some vessels may also avoid entering or departing a harbor because of bridge clearance (i.e. air gap) limitations. The economic gains potentially realized by both increased commerce and the avoidance of allisions are considerable, and a clear requirement for air gap information has been voiced by the maritime industry. Concerns over bridge allisions and resulting litigation prompted the Port Authority of New York and New Jersey (PANYNJ), the United States Coast Guard (USCG), the Maryland Port Administration (MPA) and the Port of Long Beach (PLB) to request and/or fund the development and installation of air gap sensors. Houston/Galveston and San Francisco have also expressed interest in air gap sensors. In response to these requests, CO-OPS has entered into agreements with several entities to procure a commercially available microwave air gap sensor and conduct tests and evaluations to ensure satisfactory performance of the sensor. CO-OPS evaluated three types of air gap sensor technologies that measure the air gap, (or distance from the lowest structure of a bridge to the water surface) within the navigational zone. Based on these evaluations, the microwave air gap bridge clearance sensor technology best meets the requirements for this need. After evaluations and dialogue with vendors, CO-OPS selected the MIROS SM-094 microwave air gap sensor to further test for air gap measurement applications.