Reviewing The Data; Where' Was The Data; When' Was The Data; What' Is The Data - RD Instruments WorkHorse Sentinel User Manual

13

Reviewing the Data

13.1

'Where' was the Data?

The quickest way to find out the depth of each depth cell is to display your
recorded data using WinADCP. The velocity display tells you the distance
to the center of each cell. The computed distance assumes that the speed of
sound is constant from the transducer to the depth cell. The actual distance
is proportional to the average sound speed; if the average sound speed is 1%
less than the sound speed at the transducer, the distance to the depth cell is
1% less than the displayed distance.
13.2

'When' was the Data?

The time recorded with each data record is the time of the beginning of the
first ping of the ensemble. Plan sets the ping interval so pings occur uni-
formly across the ensemble interval (as opposed to putting all the pings at
the beginning of the interval). It leaves a few seconds at the end of each
ensemble to allow time for data recording. Hence, the average time of the
ensemble is midway between the recorded ensemble time and the time of
the next ensemble.
13.3

'What' is the Data?

The WorkHorse records velocity data in units of mm/s. Calibration depends
on how well the WorkHorse knew the speed of sound (which it computed
based on its measured temperature and the salinity value it was given). A
salinity error of 5 ppt introduces less than 0.5% velocity error.
P/N 957-6163-00 (January 2001)
WorkHorse Sentinel User's Guide
page 37