Page 458 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

16.11 General rules for use of acoustic positioning systems 451
FIGURE 16.25
Relative referenced dam map with acoustic positioning.
well. This creates a scaled dock drawing where the acoustic positioning system is now relatively referenced to the drawing of the dock. Any number of combinations is possible with an understand- ing of scaled drawings and relative reference with regard to a frame of reference. Figure 16.25 depicts a scaled drawing of a dam with positioning beacons registered on the drawing.
16.11 General rules for use of acoustic positioning systems The following are some guidelines to use for acoustic positioning systems:
• The best angular resolution is broadside to the longest baseline.
• Attention to detail in placement of baseline stations is paramount due to propagation of any
baseline errors to the position resolution of the vehicle.
• Most acoustic positioning systems have a noise test capability. If in doubt about the background
noise level, test it and adjust accordingly.
• Operate all vessel equipment to be used during performance of acoustic positioning during any
noise level test.
• Carefully consider your environment type when selecting settings on your positioning system.
• If the operating platform is a heaving vessel and the frame of reference is the same vessel
(without access to a VRU), expect position dithering.
• Noise levels change constantly over the course of any operation. Consider this if loss of
positioning is experienced.
• If positional dithering is experienced, multipath is the most likely problem. Lower your receiver
sensitivity to compensate for false (multipath) readings.
(Courtesy Desert Star Systems LLC.)