Dataset: Water Level
Deployment: SensoryNCE_2014

To convert the absolute pressure to gauge pressure, atmospheric pressure readings from the nearby (~ 13 km away) weather station at Skidaway Institute of Oceanography were employed.  Gauge pressure was converted to water depth above the PT by assuming the pressure variation in the vertical direction was solely due to hydrostatic effects.  The water density was determined from the PT temperature measurement and the salinity measured at the dock, which was assumed to be equal to the salinity in the vicinity of the PTs.  Temperature and salinity were assumed to be vertically homogeneous.  To improve the accuracy of the absolute pressure readings (and thus the estimated water surface elevation), the three PTs were calibrated in a 1 deep tank at seven temperatures, ranging from 12 to 26 C.  Linear calibration curves were developed to calculate the pressure difference between two of the PTs (stations A and D) and the third reference PT (station F) as a function of temperature.  These curves were used during data processing to adjust the pressure data to a common reference pressure.  The standard deviations of the mean pressure difference between the PTs at stations A and D and the reference PT at station F were calculated for each calibration temperature.  The difference was found to be less than Pa in all cases, which corresponded to less than 1 mm of water surface elevation difference.  The water surface elevation was calculated relative to the NAVD88 vertical datum by adding the water depth data to the PT elevation using the dimensions of the stand and the GPS measurement of the antenna position.  To arrive at sufficiently accurate water surface elevation measurements, the GPS measurements were post-processed using GrafNet (NovAtel, Calgary, Alberta, Canada), treating the GPS system as a stationary closed loop network.  The system included four GPS antenna/receivers (one at each PT and one on the dock) and several Continuously Operating Reference Stations (CORS) operated by the U.S. National Geodetic Survey (NGS).  The estimated vertical accuracy from GrafNet was approximately 0.5 cm for all stations.  This level of accuracy was obtained using simultaneous GPS measurements.  The vertical positions of the PT stands did not vary during the experimental periods.

BCO-DMO Data Manager Processing Notes:
* added a conventional header with dataset name, PI name, version date
* data extracted from MATLAB .mat files to ASCII flat files to serve in the BCO-DMO system
* modified parameter names to conform with BCO-DMO naming conventions
* added approximate lat and lon of sampling location to data
* tidal_stage rounded to three decimal places
* Time format changed from matlab datenum to Date and Time (yyyy-mm-dd,HH:MM:SS)
* Data version 2 (2018-07-12) replaces data version 1 (2017-07-20) - improved metadata, added timestamp in UTC in addition to local date/time