For echosounder data products only. Currently used by the ASL Acoustic Profiler Time Series data products.
Ensemble Period
This option will cause the search to perform the standard box-car average resampling on the data. 'Boxes' of time are defined based on the ensemble period, e.g. starting every 15 minutes on the 15s, with the time stamp given as the center of the 'box'. Acoustic pings that occur within that box are averaged range or bin-wise, and the summary statistics, such as 'Data.averagedPings' are updated. This process is often called 'ping averaging'. The process uses log scale averaging, which involves backing out the dB scale to pressure, compute the weighted average, and then compute the dB scale again. Weighted averages are used when raw files bridge an ensemble period and when the data is already an ensemble or ping average.
The default value is no averaging, meaning the data is not altered. Some echosounders are configured to do ping averaging during acquisition, so the data you request with this option could already be averaged. To determine if the echosounder is averaging data as it is acquiring, check the device details page (e.g. http://dmas.uvic.ca/DeviceListing?DeviceId=22608, go to the additional attributes tab) or check the data products: see the comment field in the plots or the Config structure in mat files. Available ensemble periods are 1, 10, 15 and 60 minutes.
Calibration
This option will apply the calibration to the data, when the calibration coefficients are available. The calibration calculation and coefficients are supplied by the manufacturer. See the device details page (additional attributes tab) to see the coefficients, see the instrument documentation page, or contact us for more details. These values are also provided in the mat file Config / Cal structure - see the ASL data product page for more information.
The default value is to apply calibration when available. The alternative option will provide the raw data only. Raw data has units of raw counts, which are proportional to the received acoustic pressure.