The ability for first responders and law enforcement officers to conduct accurate and effective sonar search operations is a skill which must be learned and practised. Fire arms training and time on the range significantly improve shooting skills. There is no difference operating a sonar. Time operating the unit under field conditions is critical to successful mission out comes.
Field teams must fully understand, how to read the sonar image, how to operate the sonar and spend time drilling operations to perfect their craft. Experiments by the U.S. Navy statistically prove that additional sonar training significantly improved the sonar operators' ability to detect targets and reject false targets with far more accuracy than prior to the training.
While the SAR-law enforcement mission may differ from the military objective, the need for training and benefits from experienced instructors is not. The ability to recognize the sonar image of a drowning victim in a cluttered bottom is vastly improved if the operator has a working knowledge of sonar and has seen a library of example images. Such training should also cover how to optimize the sonar system for specific types of search operations as well as understanding the nuances of search patterns.
Side Scan Sonar Systems
Today there are a wide variety of sonar systems available to law enforcement and Search & Rescue (SAR) teams. The sonars range widely in cost and capbility. advances in technology have lowered the cost of entry.Even the most modest budgets can field a hull mounted system like the Humminbird Helix Mega a 1.2 mHz system capbable of some remarkable resolution in shallow, calm water. Teams with a more robust budget can purchase a towed system from one of several manufacturers (EdgeTech, Klein or marine Sonic technology) that increases capability. The towed systems also require a higher level of training and coordination between operator and boat driver.
Training Seminar Example
All the aforementioned skills were part of an intensive two-day side scan sonar training in Baton Rouge, LA. The event was held incooperation with the E. Baton Rouge Sheriff’s Office, with participation by the Calcasieu Parish Sheriff’s Office, the Louisiana Division of Fish and Game, and the U.S. Coast Guard Auxiliary.
Day one included 10 hours of intense classroom study focused on sonar theory and image interpretation with special emphasis on locating and identifying drowning victims. The combination of theory and field OPS allowed the officers to thoroughly understand the subject and then practice the field techniques. The classroom also included a section on crime scene evidence collection. A properly-tuned side scan sonar becomes the underwater camera accurately mapping debris and other evidence that can take dozens of hours of dive time.
Read the article: Marine Technology for Underwater Investigations by Vince Capone.
More on side scan sonar and its law enforcement applications
Side scan sonar is often only thought of as a search tool. Law enforcement personnel often will use a side scan sonar system to locate drowning victims, but did you know it can also be used to map and document underwater crime scenes?
Homeland Security officers can use the sonar for area security clearances. Sonar data taken just after an incident becomes an investigative record of the scene and can be forensically analyzed. The data provides an instantaneous snapshot of the river, lake or ocean bottom and documents debris patterns and/or the position and orientation of objects on the bottom.
Vince's data analysis of U.S. Army Corps of Engineers (USACE) sonar data provided maritime attorneys with critical evidence in a restricted waterway collision. Both vessels claimed to be on their side of the channel. A post-incident USACE side scan sonar/multibeam survey pinpointed specific debris positions on the channel bottom, confirming the actual collision position.
Whether you need training for your team or side scan sonar data collected / analyzed, you can trust Black laser Learning® to do the job. We can also provide expert witness testimony regarding underwater search and survey cases.
Law Enforcement Sonar Search Operations Skill Set Requirements
Law Enforcement search operations require a series of skills especially in the case of victim search OPS. Most importantly, once the equipment has been acquired, training and field operations are key to honing the necessary skills. Black Laser Learning® has identified team skill requirements as the following:
1) Small Boat Handling and Piloting
One team member needs to have enough small boat skills to pilot a vessel safely and follow navigational cues to drive straight and steady survey lines. Too much steerage or correcting to stay on line will degrade the sonar imagery. When the pilot finds him or herself offline, easy corrections minimize distortion in the imagery and the possibility of overshooting. The boat driver can make or break a search operation.
2) Operational Navigation and Search Planning
Phase one of any search is to gather all available information then plan the search operation. Set up a series of survey lines in the area with the required line spacing. Ensure some overlap since not even the best boat operator is online all the time.
3) Equipment Operation (Sonar, GPS, Computer and Navigation Software)
4) Sonar Image Interpretation
While not every team member must be proficient in every skill, as a functioning unit, all four skill sets are required to consistently locate and identify targets. While your boat pilot may not need to know how to operate the sonar, he does absolutely have to have the capability to navigate straight survey lines.
At least one team member should have enough experience to plan the survey. Decisions on where to search, survey line spacing and how much overlap all require careful consideration. The ability to adjust the survey plan to local environmental conditions is also critical. Current water depth bottom topography will all influence how the survey is to be conducted. At the most basic level, the operator must know how to operate and adjust each piece of gear. If the operator cannot get the best available imagery or cannot find the target due to faulty navigation, the search will be ineffective.
The field operator must insure good quality data. While the operation of equipment is a basic necessity for the boat crew, image interpretation can be conducted onshore under more stable conditions by more senior team members. All of these skills are critical and can be taught and honed with practice.
Probably one of the most difficult search operations requires locating a drowning victim without some type of vehicle or automobile to act as a guide. Without a large, easily-detectable target, looking for drowning victims alone is a difficult task requiring advanced interpretation skills and a bit of luck. However side scan sonar manufacturers often post images such as the one below which clearly show a drowning victim.
Notice how a clean, uncluttered and flat bottom makes the target easy to detect? Identification of the target is also very easy since the human figure with limbs is clearly visible.
This image was taken with a 500 kHz sonar. Normally for victim searches we prefer a higher frequency which has the potential to produce higher resolution images. Whether due to the frequency or many other factors, the victim is not always as clearly identifiable. Take a look at this next black and white sonar image, albeit again with a 500 kHz sonar.
The victims, two teenage boys, were last seen clutching each other. While there are no distinct identifying features, the alert sonar operator coupled the story along with a paired target on an uncluttered, flat featureless bottom. The sonar image was confirmed by divers and the victims recovered. Divers could have found the victims but at depths over 80 feet and with only a vague position, it would have taken several days to do what the side scan did in a few hours.
Working on cluttered bottoms, even with high frequency systems, can be challenging. The color image below recorded the final resting place of a drowning victim. However, the body was actually located by divers. The victim was not easily discernible on this image. If you cannot see the body, you're not alone. I still have trouble locating the target.
Some marine rescue teams are utilizing the Humminbird sonar system. For more information, see Black Laser Learning's Humminbird Section.