| 1. |
___________________systems can also be configured for waters-edge to waters-edge coverage (i.e., over 180 degree swath), allowing side-looking, full-coverage underwater topographic mapping of constricted channels, lock chambers, revetments, breakwaters, and other underwater structures. |
|
|
Multi-beam |
|
|
Single-beam |
| 2. |
Swath systems are typically designed with between_________________ beam spacing. |
|
|
0.5 deg and 3.0 deg |
|
|
1.5 deg and 3.5 deg |
| 3. |
Multi-beam sonar’s bottom detection thus provides three pieces of information: (1) the angle of the beam along which the acoustic pulse traveled, relative to the sonar head, (2) the round-trip travel time of the acoustic pulse, and (3) a signal intensity time series of the bottom return. |
|
|
|
True |
|
False |
| 4. |
Horizontal positioning accuracy is not dependent upon the ability of the system to compensate for pointing errors caused by vessel roll, pitch, and yaw (Figure 11-3). |
|
|
True |
|
|
False |
| 5. |
As with single beam echo sounders, the smaller the beam angle, the better the system is able to discern true depth and resolve small features. |
|
|
True |
|
|
False |
| 6. |
The electronic beam formed echo sounders use a common fan beam projector and an array of polymer receive elements physically pointed in the desired direction. |
|
|
True |
|
|
False |
| 7. |
Beam direction is determined by measuring differences in signal arrival times on an array of receive elements (phase differentiation). |
|
|
True |
|
|
False |
| 8. |
Multibeam systems are an effective quality control process on dredging projects requiring 100% bottom coverage to assess and certify project clearance. |
|
|
True |
|
|
False |
| 9. |
Multibeam systems are not recommended for payment or clearance use on shallow-draft projects. |
|
|
True |
|
|
False |
| 10. |
Multibeam sensors cannot be configured to detail pipelines, bulkheads, flood walls, lock walls, revetments, breakwater riprap, and other similar underwater structures. |
|
|
True |
|
|
False |
| 11. |
Multibeam survey systems represent an effective mechanism for detection of shoals, rocks, wrecks, debris, or other navigation hazards lying above grade in a navigation channel. |
|
|
True |
|
|
False |
| 12. |
Multiple-transducer, boom-mounted, channel sweep systems are generally preferred for use over multibeam survey systems in shallow-draft (<15 to 20 feet), sand/silt-bottomed navigation channels. |
|
|
True |
|
|
False |
| 13. |
Multibeam systems are normally ______________ utilized on small, mobile survey vessels up to 26 feet in length, with the transducer assembly externally mounted over the side. |
|
|
More cost-effectively |
|
|
Less cost-effectively |
| 14. |
Alignment and offset parameters must be measured for the various sensors making up the multibeam system, e.g., gyro alignment/offsets, transducer mounting angles/offsets, DGPS antenna offsets, static and dynamic drafts, vessel settlement/squat, and estimated latencies. |
|
|
True |
|
|
False |
| 15. |
A performance test is not a quasi-independent test which is not used to assess the quality of data being collected and to verify conformance with the prescribed accuracy specification or object detection requirements for the project. |
|
|
True |
|
|
False |
| 16. |
Static offsets of the sensors are the distances between the sensors and the reference point of the vessel or the positioning antenna. |
|
|
True |
|
|
False |
| 17. |
_______________ is the depth of the transducer head below the waterline of the vessel. |
|
|
Transducer draft |
|
|
Transducer offset |
| 18. |
The multibeam transducer should not be installed near to the centerline of the vessel and level about the roll axis. |
|
|
True |
|
|
False |
| 19. |
The__________ should be aligned with the x-axis of the vessel using an electronic total station and geodetic control points. |
|
|
Gyro |
|
|
Squat |
| 20. |
Time delay in the positioning is the ______________ between the time positioning data are received and the time the computed position reaches the logging module. |
|
|
Time lag |
|
|
Time lead |
| 21. |
Patch tests are periodically performed to quantify any residual biases in the initial alignment measurements described previously. |
|
|
True |
|
|
False |
| 22. |
The maximum speed may be calculated by the following equation:
v = S • d • tan (b/2)
where sounder sampling rate per second is denoted by ____. |
|
|
S |
|
|
b |
| 23. |
The following equation a = tan -1 [( da / 2 ) / (depth) ] denotes ___________. |
|
|
Pitch offset |
|
|
Along-track displacement |
|
|
Water depth |
| 24. |
The following equation y = sin -1 [ ( da /2 ) / XI ] denotes |
|
|
Azimuthal offset |
|
|
Relative across track distance |
| 25. |
The roll offset can be estimated by the following equation: r = tan -1 [ ( dz / da ) / 2 ]. This equation is for ____________. |
|
|
Small angles of less than 2 deg |
|
|
Small angles of less than 3 deg |
|
