[Acoustics] Using ADCP equipment for bathometric surveys

[Tracy Vermeyen]

Hi Daniel,

I have been performing bathymetric surveys with a Rio Grande ADCP for
the last few years with success.  I have performed surveys using
hand-held GPS to get a starting position (northing/easting) then using
ADCP bottom tracking data (distance travelled north/east) to compute a
N/E for each ADCP depth measurement.  This works well when water surface
elevations are not of concern.  For example, on a lake or reservoir, or
near-field survey of a hydraulic structure.  Much of this work has been
in support of 2-D and 3-D hydrodynamic modeling, so it has included
collecting velocity profiles along with the bathymetry data.

I have also brought RTK GPS data into the ADCP software, WinRiver,
which is survey grade (1-2 cm-accuracy) on both horizontal and vertical
position.  Using RTK-GPS increases the accuracy but also the time, cost,
and effort to perform a bathymetric survey.  Using RTK GPS is required
when performing a survey on a river where water surface elevation is
important.  

I have incorporated a digital depth sounder as a vertical beam to
measure depths directly beneath the ADCP and GPS receiver.  Using a
depth sounder simplifies data processing and removes the uncertainty
associated with averaging 4 depths measured by the 4 inclined ADCP
beams.  Using the ADCP depth is a concern especially in areas with steep
banks, non-uniform bottoms (think dunes or scour holes) or vertical
walls.

As far as software goes, I have written utilities to extract the
(x,y,z) data from a ADCP ASCII data file, then the data is processed
along with the RTK-GPS data to match the depths with the appropriate
post processed RTK GPS positions using Time, position, or Ensemble
number to compile depth data with water surface elevation.  Post
processing can be easily done in a spreadsheet.

There is a package out there called HyPack
(http://www.hypack.com/hypack.asp) that claims to be able to do
bathymetric surveys using ADCPs in place of fathometers. But I do not
have experience with this package.  I know the US Army Corps of
Engineers use this package, so maybe they can relate their experiences.

Hopefully, this short description meets your needs.  If you can contact
me for more information.



>>> "Daniel Hannon" <Daniel.Hannon at dnr.nsw.gov.au> 02/20/06 07:23PM
>>>
I've been looking at ADCP use here at Tumut NSW Australia, but
[although
we have many sites] cannot justify it unless I can find other uses for
it.  Because we are in the headwater area of the catchment, we only
have
say 5 sites were we would use an ADCP more than once a year.  Most of
our sites are wading depth and too shallow for [and/or no advantage
in]
an ADCP.
 
Therefore I was trying to get out of the suppliers an answer as to
whether their [sontek/rdi] ADCP was capable of and software is
available
for - not only stream flow measurement - but bathometric survey.  And
-
if they are capable of it and the software will produce 3d plots and
allow multiple transects or slices [XS's] - I am aware that they can
be
connected to GPS, so essentially ADCP's have the capacity to do this
sort of task, the equipment could easily do what I am proposing,
software may be a problem.  
 
Has anyone used one like this, is the software available?
 
 
 
 
Danny Hannon,
Natural Resource Officer - Hydrographic
Murray - Murrumbidgee Region,
TUMUT   NSW   
phone  0269470209
mobile  0427692675
email:daniel.hannon at dipnr.nsw.gov.au 


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