A self-locating datum marker buoy (SLDMB) is a drifting surface buoy designed to measure surface ocean currents. The design is based on those of the Coastal Ocean Dynamics Experiment (CODE) and Davis-style oceanographic surface drifters – National Science Foundation (NSF) funded experiments exploring ocean surface currents. The SLDMB was designed for deployment by United States Coast Guard (USCG) vessels in search and rescue (SAR) missions and is equipped with a Global Positioning Satellite (GPS) sensor that, upon deployment in fresh- or saltwater, transmits its location periodically to the USCG to aid in SAR missions. Additionally, SLDMB are deployed in oceanographic research in order to study surface currents of the ocean.

Because it has a small above-water surface and high underwater surface area, the effect of surface winds and waves has a negligible effect, instead moving with the flow of the upper 1m of the water column.

Deployment of the SLDMB may be accomplished by aircraft (both fixed-wing and rotary) or by ship. Electronics consist of a GPS receiver, electronic transmitter and sufficient batteries to provide continuous data collection for a period of two weeks to one month.

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