| 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 |
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