[Acoustics] Divergence in data from field vs playback

[Rainville,François [CIS-WSB]]

We have now often witnessed a difference between Q as initially produced by the ADCP (apparently still live in the computer memory. As seen within F12. Info kept in the Survey Notes by the Operator) and the Q for the same transects during the playback of recorded data files.

Most of the time, the differences in values are only seen in the least significant digits but we have also seen examples where this was not the case. In one situation, the difference was 247 versus 244.6 cms for a transect. This is clearly a case where significant figures as prescribed by our standards at WSC (i.e., 3 significant figures. Max 3 decimal places.) were also affected.

- Has anyone else witnessed such discrepencies between raw data/field notes and played back data?
- Does anyone have an explanation for this phenomena?

Thanks, F.

Francois Rainville
Standards Technologist
Water Survey of Canada
613-992-1673