Document1
COVIS SONAR PARAMETERS AND SETTINGS
Revision History
DATE
EDITOR
12-14-09
Jackson
12-14-09
Light
12-14-09
Light
COMMENTS
Origination
Format edited
Minor editing, changed absolute values in terminology
to more generic N
1
Document1
1.0 INTRODUCTION
The following values for sonar parameters and settings are targets, not rigid
specifications. The final values will be determined on the basis of limitations of the
sonar as well as tradeoffs between accuracy, data acquisition time, file size, etc.
2.0 TERMINOLOGY
Term
Mode
Ping
Scan
Sweep
Run
Sequence
Description
Refers to plume imaging, plume Doppler, or diffuse flow
One sonar transmission
Set of pings at one elevation angle. Note that the word “scan” does
not imply use of the rotator. A scan covers an azimuthal sector with
256 beams, formed electronically
Complete sweep in elevation, comprised of N scans, except for
diffuse flow, where a fixed elevation is used
Complete data acquisition in one mode, comprised of 1 to N sweeps.
In diffuse mode, Scan = Sweep = Run
Complete set of runs spanning all modes including sonar
repositioning between runs
3.0 SONAR PARAMETERS AND SETTINGS
The following two tables give proposed sonar parameters and settings. It is hoped
that many of the settings can be changed during the early stage of the deployment in
order to respond to unanticipated issues.
3.1. Common Parameters/Settings
Parameter
Frequency
Digitization Window (re end of transmit)
Horizontal Beamwidth
Number of Beams
Azumuthal Sector Covered in one Ping
Average Vertical Sidelobe Level
Average Horizontal Sidelobe Level
Value
200 kHz
0-80 ms
0.5°
256
130°
-26°
-34°
2
Document1
3.2. Mode Dependent Parameters and Settings
Parameter
Pulse Length
No. Pings/Elevation
Initial Elevation
Time Interval Between
Pings at Each Elevation
Elevation Range1
Elevation Increment4
Time Between Elevation
Increments
No. Pings/Sweep
No. Scans/Run
Time to Complete Run5
Vertical Beamwidth
Digitization Rate
(No. I, Q /second)
Plume Imaging
0.3 ms
2
15°1
100 ms
Plume Doppler
1.5 ms
10
15°1
100 ms
Diffuse Flow
0.3 ms
5
-15°, 0° 2
100 ms 3
75°
±1°
1s
75°
±1°
2s
NA
NA
NA
120
4
4 min
1°
> 6 kHz
600
4
8 min
1°
> 2 kHz
5
2
2s
27°
> 6 kHz
Table 3-1
1The
initial elevation and elevation ranges given here are nominal values. The
actual values will be set after deployment and depend on the geometry of the
smoker.
2It
is assumed that two different diffuse flow images will be obtained. The
negative (downward) elevation is for diffuse flow on seafloor. Zero elevation is
for diffuse flow on edifice.
3This
interval depends on frequency, 400 kHz assumed.
4For
plume imaging and Doppler, the sonar sweeps in both upward and
downward directions.
5This
does not include time to set sonar angles at their initial values.
3.3. Sonar Schedule
A straw man schedule of sonar events will be given in order to promote
discussion. Just to exercise the nomenclature above, note the collection of all
events below is a sequence and that there are four runs in three different modes
(plume imaging, plume Doppler, diffuse flow).
Event
Pan and tilt to starting
position for plume imaging
Acquire plume imaging data
Acquire plume Doppler
data1
Required Time (sec)
10
Elapsed Time (sec)
10
240
480
250
730
3
Document1
Pan and tilt toward edifice
diffuse flow region
Acquire diffuse flow data
Pan and tilt toward seafloor
diffuse flow region
Acquire diffuse flow data
5
735
1
10
736
746
1
747 = 12 min, 27s
Table 3-2
1No
time is required for positioning of sonar as the Doppler scan begins at
ending position of imaging scan. The ordering of runs above was chosen in an
attempt to minimize the use of the rotator and flexing of cables.
4