[Acoustics] false bed

[David S. Mueller]

Nick,

At 2.4 MHz I would expect very little penetration even in silt. The first
thing I would check is the salinity and temperature in those data. A speed
of sound error is a likely source of this behavior. 

David S. Mueller
U.S. Geological Survey
Office of Surface Water
9818 Bluegrass Parkway
Louisville, KY 40299

dmueller at usgs.gov

Voice: 502-493-1935
Fax: 502-493-1909
Mobile:502-558-5907


-----Original Message-----
From: acoustics-bounces at simon.er.usgs.gov
[mailto:acoustics-bounces at simon.er.usgs.gov] On Behalf Of Nick Wray
Sent: Friday, March 17, 2006 7:28 AM
To: acoustics at simon.er.usgs.gov
Subject: [Acoustics] false bed


Whilst using a stream pro 2.4Mhz to gauge a section of slow river that
had a bed of light silt (no moving bed)   the depth recorded was deeper
than measured by staff. Is the ADCP ping being absorbed slightly by the
silt before returning the echo hence measuring a deeper depth.and
therefore a greater area than actual.

Nick

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