What lies Beneath |
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This article has been reproduced with the consent of the author. John Easton is a passionate bass angler who knows his electronics. Gain some insight into the world beneath the waters. Our compliments to John, a true angling master. When trolling a body of water one has two choices, throw a line out the back and hope for the best or get to know what’s under the water as well as you know what’s above the water. When I say above the water, what I mean is:- when you pitch that little weightless fluke just under an over hanging branch, or right into a tiny hole in the grass, you are making the best presentation possible by being accurate, and thus improving your odds dramatically. Now, would that fish that was under the branch in the lovely shade from a hot day, or that big ol’ bass sitting hiding in the grass planning an ambush, leave their spots and come all the way out to a really poor cast/presentation? So why would this be any different at 10ft, 30ft, or even +60ft? In this example below I have taken the top end of Durban Bay at Inanda Dam in KZN to explain how one can get to know their dams from a different perspective. I have heard many people say “I can remember all the spots and the drop-offs that I have found on my ‘fish finder’.” All I can say to that is that you must have an incredible memory. The first thing you will need is a sounder that has a recording/logging feature. Most of the colour Lowrance units have this feature, just many users don’t know that it is there. The unit I use for this is the Lowrance LCX37c because of the big 8” bright and super sharp screen, but the smaller entry colour units will do exactly the same job. Then you will need a high speed SD memory card, either the Lexar Professional 60X, SanDisk Extreme II 60X or ultimately the Extreme III 133X. Normal SD cards do work but let you down sometimes in the middle of a recording and you will only realize this once you get home and view it on your PC! Then you will need to download SonarViewer® from the Lowrance website in order to play these recording back on your PC. You are now ready to hit the water. Make sure that you record the exact dam level and that all your electronics settings are done before entering your area you plan on recording, and split the screen to sonar/map. I recommend splitting the screen 30/70 in the map’s favour, it just makes keeping your track distances equal, easier. Then start recording while idling and zig-zag up into the bay, as seen in image below. The white trail that you see in the image below is the actual trail recorded by the Lowrance and then saved as a Google file (.kml). When you reach the end, stop recording. This is the easy part, the hard part comes once you get home. Inanda Dam KZN – Google Earth with trail:  Download the logged data from your unit by removing the SD card, and download to your PC. Open this file with SonarViewer® and play back using play/pause/FF/FR/stop, just like you would with Windows Media Player. At all the points of interest (POI), such as drop-offs and humps, pause, move your cursor to the POI and jot down the Bottom Depth, longitude and latitude. The main POI’s you will need to record is the deepest and shallowest points of each of the zig-zags, but remember the more info you record, the more detailed your chart will be. SonarViewer:  The recordings below are the actual profile of Durban Bay (Zig-Zag Trail): 
Once you have captured all this data you now have the required info to create a 3D image of the profile because you have the X (longitude), Y (latitude) and Z (depth). 3D Plotting:  At this point you can either plot a rough sketch of all this info or you can get acquainted with a CAD (Computer Assisted Drawing) program such as AutoCAD, and create a perfectly scaled image of your recordings. The beauty of this is that you can edit this drawing later with the long/lats accurately as you find new structure, and just add to it. For example you can add man made structure such as old foundations, cars, PVC ‘brush piles’, tyres etc. or natural structure such as lay downs, standing structure, natural brush piles etc. using your Side Imager. Note the stars on the CAD image with the SI images below of man made structure. (red dots on the Google Earth image on the first page). Rendered AutoCAD 3D image of Durban Bay (top section  Left Star: (Side Image)  Right Star: (Side Image)  As time goes on you will have as much info on what’s happening under the water, as what you can see on top of the water. Always remember that trees on top of the water get bigger as time goes by, because they are alive and growing. Whereas natural structure under the water is decaying as it is dead, and as a result becomes smaller, especially brush piles pulled into the water by other anglers. Do not forget to record dam level before recording, this can really confuse you when the dam level changes drastically. |
