The map layer displays observations from automated and manual reporting stations at airports (e.g. ASOS) stations maintained by NOAA/NWS, FAA, or DOD, NWS' Coastal-Marine Automated Network (C-MAN) stations, NWS' Moored Buoys, NOS' Physical Oceanographic Real-Time System (PORTS), and ships participating in the Voluntary Observing Ship (VOS) program.

In addition, observations from some regional observing systems are also displayed including the Gulf of Maine Ocean Observing System (GoMOOS). Presently, observations from NOS' National Water Level Observing Network (NWLON) are not displayed.

Significiant wave height is the average wave height of the highest 33% of all individual waves during a specified time sampling period. If a mariner was to observe the passage of 100 individual waves past a given point, the significant wave height would be the average height of the highest 33 waves. Significant wave height tends to be the height of the waves that is most readily observed by the human eye. NowCOAST displays significant wave height data from both buoys and ships. Wave observations at buoys are estimated from data from accelerometers or inclinometers on board during a 20 minute sampling period. Wave observations from ships are made by observers usually on the side of the ship form which the waves are coming. The quality of the wave observations from ships depend on the observer's training, size of the vessel, and the height at which the observation is taken.

The latest observations from NOS stations as well as other platforms can be found by going to nowCOAST's Meteorological map layer under 'Geo-Referenced Links/Observations - In-Situ Stations:'