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Structure Scan
By Capt. Alan Mullis

   I can’t begin to talk about Structure Scan without first touching on the HDS units themselves. Lowrance HDS units are available in a 5”, 7”, 8”, and 10” screen size. The five and seven inch screens only split in two panes while the eight and ten inch will give a four panel view. The eight and ten inch screens also have convenience buttons and a zoom wheel behind the cursor control. However, the five inch unit will do anything the ten inch unit will do; you just have to menu through until you find the adjustment you are looking to change. One of the most prolific complaints I hear is “I just bought my Lowrance unit four or five years ago and now it’s out dated.” Well, I believe that Navico has helped to solve that problem with the Plug & Play head features of their Lowrance and Simrad units. With the help of a NMEA 2000 starter kit and/or an Ethernet cable, options like the LWX-1 Sirius Weather and radio antenna/receiver, BR24 Radar, EP Temperature sensor, EP Fuel Flow sensor, EP Fuel Level sensor, Sonic Hub, other HDS units, LSS-1 Structure Scan, and many other options can be plugged into these heads for years to come.

   Structure Scan Sonar, unlike competitors units, combines the Broadband Sounder with Side Scan and Down Scan Imaging into one powerful angling tool. When Broadband Sonar is overlaid on the Down Scan Imaging it removes the guess-work and reveals fish and structure more accurately than either do alone. The Track-back feature allows the angler to scroll through sonar history and Chart Plotter trail (from either sonar or Structure Scan) and display and mark waypoints while continuing to record data and reviewing history. Structure Scan can easily be networked with up to three displays without the expansion port to allow viewing of Structure Scan on all displays on the network.

     The Side Scan full screen view will give detailed imaging with 480 feet side to side coverage underwater. The Down Scan allows you to see images under the boat exactly as they appear. When Structure Scan is used on a split screen with 2-D sonar a better understanding of 2-D sonar can be obtained.

The LSS-1 consists of a box and a transducer with three crystals inside projecting straight down and both left and right. The two frequencies used are 455 and 800 which will not interfere with 83/200 transducer. The two transducers should be mounted within 18” of each other so the Broadband Sonar can overlay the Down Scan Imaging for better fish detection. When using the lower 455 kHz output, the system provides clear sharp side scanned images on both left and right out to 250 feet, as well as down scanned images to a maximum depth of 300 feet. Switching to the higher 800 kHz output further increases image definition while sacrificing some distance in range.  When a Structure Scan window is active, you can press the menu key which will bring up the Structure Scan menu. Here you can select one of eight color palettes and then select display options. Every time a new palette is selected the contrast and sensitivity should be adjusted to display the best picture. Remember that fish will appear as bright specks and not arches when using Structure Scan due to the narrow cone.

    Remember, when recording sonar, always save it to an MMC card or the hard drive will fill up very quickly. The larger the side scan distance the smaller the targets will be. The longer the shadow the taller the object, the longer the fish shadow the higher in the water column the fish is holding. A short shadow indicates the fish is closer to the bottom. Sometimes the surface clutter will look like a school of bait fish, but you can usually tell the difference because the surface clutter will extend downward from the top of the water column.

  Unlike our competitors, Lowrance Structure Scan gives us great images from two through ten mph and good images from ten to thirty mph. This makes it an ideal tool for eliminating water for the tournament angler. Docks and structure can be scanned to show if fish are present or not. Many of the anglers that I talk to that use Structure Scan say they are still fishing the same structure but with Lowrance’s state-of-the-art Structure Scan they now fish it the right way because now they “Get the Whole Picture”.

   There are several companies that offer good training videos for both HDS Units and Structure Scan. My favorite is from Dr. Sonar but Bennett Marine has some good information as well.