Figure 3 - uploaded by Kevin Ellard
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The Apama demonstrating roll capacity. The image shows it inverted, after having roll past 180-degrees.
Source publication
Report describing work undertaken during Phase 2 of the Tasmanian ROV Project. The project focused on design ROVs for marine pest surveillance and inspection.
Contexts in source publication
Context 1
... 1: BRH ROV developed during Phase 1 many other similar types of ROV. Figures 3 and 4 below show the Apama's pitch and roll capacity demonstrated during pool trials. These capabilities can also be viewed in training video 5. ...
Context 2
... units typically use a wide vertical beam and a narrow horizontal beam to produce a series of narrow image slices. The mode of operation is represented in Figure 30, where the transducer beam repeatedly records a section as the transducer head rotates. These signals are then combined into an image displayed on the screen. ...
Context 3
... 360-degree scans, referred to as polar scans, produced by SBSS provide a top-down view of the environment surrounding the ROV, as shown in Figure 31. When only a portion of the periphery is scanned, as displayed in Figure 32, it is referred to as a sector scan. ...
Context 4
... to refresh the ROV or target objects can move resulting in residual images left on the screen. This effect is illustrated in Figure 33 which shows a row of pylons associated with wharf infrastructure. Pylons marked 'A' and 'B' can clearly be seen on the video display and are true images, but pylons marked as 'C' are residual images caused by the ROV rotating 90 degrees clockwise before the image is refreshed. ...
Context 5
... simultaneous use of multiple acoustic beams provides higher image refresh rates than SBSS and can provide greater resolution. As illustrated in Figure 34, being restricted to sector scans MSS so are normally mounted on the front of ROVs to give a forward view. ...
Context 6
... quality can be affected by multiple factors and therefore will vary accordingly. Under optimal conditions MSS can produce three dimensional images of significantly higher quality than SBSS, with Figure 35 illustrating the quality of image that can be achieved. Here the combination of high-quality MSS unit used, the smooth solid face of the dam wall providing a good surface for echo, the sharp edges of the water intake channels and lack of suspended material in the water, all combine to produce the image shown. ...
Context 7
... baseline systems SBL systems consist of an array of receivers lowered into the water at known locations around a surface base-station. As illustrated in Figure 36, these measure time taken for each receiver to register an acoustic signal. The relative difference between each is then used to calculate position via a method of triangulation. ...
Context 8
... calculate position the range, bearing and slant angle of the ROV relative to the surface transducer are calculated ( Figure 37). Internal clocks within both the ROV mounted and surface transceivers are synchronised so that they work in unison. ...
Context 9
... DVL transducer head transmits a minimum of three narrow acoustic beams that are orientated in slightly different directions so that any movement will cause the frequency of one or more of the returning echoes to shift (Figure 38). If the ROV is moving towards the echo, the apparent frequency of the sound wave will be higher because the returning echo has less distance to travel. ...
Context 10
... unit is very compact, easily installed, and, at approximately $350 US, comparatively inexpensive. Figure 39 shows the ping SONAR fitted to the rear of the BRH, whilst Figure 40 shows an example of the display produced. As previously mentioned, one of the most important uses of SSBS in marine pest programs is as an altimeter to maintain constant distance between the ROV and seabed when conducting benthic surveys. ...
Context 11
... from the obvious difference of one being a sector scan and the other a polar scan, both units are detecting targets between ranges of 30 to 40 meters. Figure 43 identifies divers in the water (A) and Figure 44 shows two rows of wharf pylons (B). Our impression was that apart from the continuously updated colour display, the quality of image produced by the MG and the Ping 360 were similar. ...
Context 12
... varied depending on the complexity of the task and number of turns undertaken. Figure 53 shows the difference in estimated versus GPS position for the DVL-75. The combination of DVL and GPS proved to be a useful combination for validating position and improving overall accuracy of transects. ...
