Page 34 - The ROV Manual - A User Guide for Remotely Operated Vehicles 2nd edition

22 CHAPTER 2 The Ocean Environment
2.2.17.2 Refraction..........................................................................................................44
2.2.17.3 Scattering...........................................................................................................44
2.3 Ocean dynamics..............................................................................................................................45
2.3.1 Circulation.................................................................................................................45
2.3.1.1 Currents.................................................................................................................46 2.3.1.2 Tides......................................................................................................................47 2.3.1.3 Watervelocity.........................................................................................................48 2.3.1.4 Waves and the Beaufort scale................................................................................. 48
2.3.2 Effects of wave pattern upon ROV operation.................................................................. 51
In order to comprehend the concepts of operating in the ocean world, an understanding of the details of this environment is needed. The content of this chapter explores the makeup of fresh water and seawater and then goes into the interaction of this substance with the world of robotics. We will explore the basic concepts of water density, ocean circulation, currents and tides and how each of these affects the operation of ROV equipment. Armed with a general knowledge of ocean- ography, work site predictions may be made on such variables as turbidity (affecting camera optics), temperature/salinity (affecting acoustic equipment and vehicle buoyancy), tide and current flows (affecting drag computations on the submersible/tether combination), and dissolved gases (affecting biological population). This section condenses information from complete college curric- ulums; therefore, for further details, please see the references in the bibliography. Special thanks go to Steve Fondriest of Fondriest Environmental, Inc. for his contribution to the fundamentals of environmental monitoring and data collection instrumentation.
2.1 Physical oceanography
2.1.1 Distribution of water on earth
Earth is the only planet known to have water resident in all three states (solid, liquid, and gas). It is also the only planet to have known liquid water currently at its surface. Distribution of the earth’s water supply is given in Table 2.1.
As shown in Table 2.1, most (97%) of the world’s water supply is in the oceans. Water can dis- solve more substances (and in greater quantities) than any other liquid. It is essential to sustain life and is a moderator of our planet’s temperature, a major contributor to global weather patterns, and, of course, essential for operation of an ROV.
The oceans cover 70.8% of the earth’s surface, far overreaching earth’s land mass. Of the ocean coverage, the Atlantic covers 16.2%, the Pacific 32.4%, the Indian Ocean 14.4%, and the margin and adjacent areas the balance of 7.8%. It is also interesting to note that the Pacific Ocean alone covers 3.2% more surface area on earth than all of the land masses combined.
2.1.2 Coastal zone classifications and bottom types
General coastal characteristics tend to be similar for thousands of kilometers. Most coasts can be classified as either erosional or depositional depending upon whether their primary features were