Intro to SONAR Sonar (The Latter Also Referred to As Radial Or Mechanically Scanned)
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INTRO TO SONAR By Mark Atherton Arthritis and Scuba Diving Fractures, Surgery and Acute Conditions Herniated Disc Disease 1-10-1 Rule For Cold Water Survival Greetings after 9/11 have already come and gone and were likely there for the profit potential and moved on when they In this issue we present another aspect of technology for discovered how difficult it is to sell to municipalities or when your dive team. In years past we introduced ROV technology Homeland Security monies became more difficult to obtain. that led to some crossover into sonar but we never had the We can find no flaw in that, profit is what keeps companies same technical background or available expertise with sonar alive, pays the bills, provides jobs etc. to offer educational articles. This issue offers the FIRST of a series of articles on sonar technologies by Mark Atherton. Grant money is drying up rapidly and it is getting harder and Mark and I met at the Underwater Intervention in New harder to obtain the kind of financial assistance that was Orleans years ago and he was instrumental in getting available in the years immediately following the 9/11 attacks Kongsberg Mesotech to join our Sponsor family. Mark is the in 2001. Personally I do not see that changing much over author of Echoes and Images, The Encyclopedia of Side- the next decade; maybe the next two. Scan and Scanning Sonar Operations (http://www.echoesandimages.com) and has agreed to write What HAS happened though is we have become recognized a series of progressive articles on sonar technology for as a genre specific diver discipline. Companies are now PSDiver Monthly. recognizing that we exist, have different needs in both training and equipment and know the difficulties we face in It is my belief that the Homeland Security monies that were funding. Because our numbers are as large as they are, we offered after the 9/11 attacks helped facilitate the DO represent a very viable potential market for particular introduction of new and advanced technologies into our field businesses. Those who have managed to break into our and discipline of diving. world have been able to modify certain products that make them more useful or safer for us to use. Consider what the This introduction led to a number of teams recognizing a dry suit companies have done over just the last 10 years. need and application of those technologies then applied for Material has improved, seals are better and more user and received grants and equipment. Most of the teams who friendly and cost has come down in some instances. Some applied and received it likely never had a budget for the companies are even manufacturing a PSD dry suit that is equipment and would not have been able to obtain it without designed in both form and function for US. the assistance of those Homeland Security Grant monies. Dry suits used to be thought of for just cold water diving and At the same time, our discipline of diving became more and occasionally were referenced for use in polluted water. Being more evident to a larger audience and businesses saw a stubborn, most of us considered our wet suits capable of potential market for product and services. Perhaps the doing cold water diving and we did not worry about polluted potential for sales and service was artificially enhanced by water unless we were asked to dive in a cess pool and THEN the large numbers that were given via Homeland Security. we would say, “Not without a dry suit”. Until recently, we still considered diving with a dry suit and FFM one of the Those companies who existed before 9/11 and supported us safest ways we could dive and be protected. We were either had already recognized and respected us or the wrong. Something as simple as the exclusion of part of the service we provided, and worked to support us within their equipment that was really necessary was not touted until own system. Some of the companies who “discovered” us just a few years back. We have to ADD a dry hood to the dry PSDiver Monthly Issue 99 2 suit and FFM in order to truly protect a diver. Even then, As you read through the pages of PSDiver Monthly, pay there is a potential for exposure. attention to our advertisers. They are part of our PSD family and we consider them sponsors much more so than just The technologies that we encounter and can adapt to our advertisers. When you have a question about their product discipline of diving are amazing. There is a device that will and call them, identify yourself as a subscriber of our allow you to see through zero visibility water. It can be magazine and let them know you are a PSDiver. You will handheld with a heads-up display discover the difference. or used on an ROV without splashing a diver. They are not We will always need our divers cheap but are far less than what I regardless of the tools we have value MY life or ANY of my dive available. It will be up to us to team member’s lives. continue to learn, to train, to adapt and to build and support Imagine the ability to drop in a our diving discipline. piece of equipment that will use sonar and map an entire area WE have managed to make great before splashing a single diver. strides in the last couple of years Imagine the opportunity to use towards this goal. Though slow, different types of sonar the newly founded Water equipment in combination with an Response Training Council should ROV with the ability to grasp an become a catalyst for change and object and return it to the www.G-dive.com help us as a whole to become surface. How much risk is there NEW SPONSOR! recognized and respected as a to our divers if they never have to distinct discipline of diving. get in the water? Each year I try to find new sponsors for the magazine. Unfortunately we can imagine all we want because the Believe it or not I am selective. There are some companies reality is that equipment, while available, is probably not who are not a fit or do not understand what we do and just within the financial range of the vast majority of dive teams. want to access our subscribers. While I have to have funds to run the magazine, I do my best to make sure we fit our But with time and innovation, I am confident these types of sponsors as much as they fit with us. With that in mind, equipment will eventually find their way into our trucks and welcome Gary Haddon and G-Dive to our Sponsor family. become some of our standard and primary tools. It is cold out. Stay warm and DIVE SAFE! These types of technology have existed for many years. Some have been applied to search and recovery almost Mark Phillips since their inception but only as a side note to their main If you would like to discuss this topic or any other, join business. In today’s world, specialty products that fit and Editor / Publisher PSDiver Monthly our discussion group: meet our needs are being developed and brought to market. CLICK HERE TO JOIN PSDiver Monthly Issue 99 3 Cover Photo provided by John Drewniak Whites Dry Suits Quick History: Special to PSDiver The two primary types of acoustic equipment used for underwater search operations are side-scan and scanning Intro to SONAR sonar (the latter also referred to as radial or mechanically scanned). Side-scan, commercially available since the PSDiver Monthly MINI Series of Sonar early 1970s, is the “wide-area” search tool but the ability to resolve a body-like target wasn’t consistently possible Articles until higher frequency systems (500kHz and higher) By Mark W Atherton © entered the market in the mid-1980s. Scanning sonar appeared in 1983 and with an initial frequency of 675 Your team has taken possession of side-scan sonar and kHz, its applicability for body search was immediately its delivery included two days of manufacturer training. recognized. “The instructor was GREAT but there were seven trainees Is there one “best” system to have? Side-scan and trying to learn the system and the amount of information scanning sonar are amazing but different tools – each imparted to us in that short time was - overwhelming! with very specific operational strengths and weaknesses. That was two months ago; we’ve just received a call a boat has been found overturned and two people are Fact: Both instruments need to be in the SAR team reported missing. The local news is covering this incident toolbox! and because we have this new side-scan sonar, we’re reportedly the ‘search experts!’ The reality is we’re still SONAR (as defined by the Merriam’s Webster learning how to hook it all up and turn it on!” Dictionary): SO-NAR \′sō-när\ n [sound navigation ranging] (1945) : As a sonar instructor, I’ve heard this scenario too many a method or device for detecting and locating objects times. especially underwater by means of sound waves sent out to be reflected by the objects ; also : a device for Over the next year, PSDiver Monthly is publishing a series detecting the presence of a vessel (as a submarine) by of articles on sonar operations and will cover topics not in the sound it emits in water. the instrument’s Operator Manual – information and “tricks of the trade” to get your sonar up and running, Interestingly enough, there are references that Ted Hunt, your search done right and better prepare you to Director of the Harvard Underwater Sound Laboratory in complete sonar data interpretation.