"The National Oceanic and Atmospheric Administration (NOAA) National Ocean Service (NOS) Center for Operational Oceanographic Products and Services (CO-OPS) is responsible for developing and maintaining the National Water Level Observation Network (NWLON). CO-OPS, like most operational, technical programs, analyzes state-of-the-art and emerging technologies to identify potential improvements in data quality and operating efficiency and to maintain core expertise for authorized missions. A critical challenge facing CO-OPS is to ensure that water level measuring technologies are capable of delivering data that meet prescribed accuracies, are reliable and resilient in harsh environments, offer improvements in deployment, operation and maintenance efficiencies, and are expected to have a reasonable life-of-industry support for parts manufacturing and service. The ocean observing community has recognized that microwave radar technology, which was previously developed for various range measurement applications, also offers many potential benefits for long-term water level monitoring. In response, the CO-OPS Ocean Systems Test and Evaluation Program (OSTEP) conducted a series of extensive laboratory and field tests on a set of four types of microwave radar sensors from four different manufacturers to determine their suitability for use at NWLON stations and other locations where CO-OPS requires long- and short-term water level measurements observing systems. Analysis of data collected by the selected four sensors over the last 2.5 years of testing points to the Design Analysis WaterLog® H-3611i radar sensor as the best suited for CO-OPS measurement applications at this time. Analysis included an assessment of the four sensors' water level measurement performance over a broad range of environmental variability. Sensor selection was based on quantitative criteria and a related scoring method specifically designed with CO-OPS' unique operations and applications in mind. All four sensors demonstrated similar measurement accuracy capabilities, and their scores were very close. However, specific aspects of each sensor influenced the choice of the WaterLog® sensor for this application. Testing of newer versions of the other three sensors, as well those from other manufacturers including Design Analysis, may continue, and they may still be considered for use in CO-OPS operational water level stations. Results presented in this report, however, focus only on measurements collected from WaterLog® radar sensors"--Executive Summary.

National Ocean Service (NOS)