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I bought a Humminbird 1197 Fishfinder in April 2008 primarily because it is about the only one with a
side scan view that was marginally affordable. The manufacturers advertising and simulator imagery from
the units seems aimed mostly at finding structure like bridges and trees growing out of the bottom of newly
formed fresh water lakes. The Chesapeake has precious little structure to look for but I hoped it would make
the search for bait fish easier. I hoped it would show if I had just run over the middle of a school or if it was just the edge of a big school off to the right so I would know which way to circle. As of yet I am not sure if it helped that much more than just the down looking rig in finding the bait, but it has certainly given me a better picture of what is down there and a lot of help in interpreting what the down looking image means. One feature of the unit is that it takes a standard SD memory card, same as a digital camera and with a push of a button it saves a waypoint along with a screen shot of whatever the screen is showing. It saves it in a PNG format similar to a JPG so you can stick the card in the computer and look over the saved images, (or put them up on the internet). There are a lot of available screen views and combination views but the one I use most is a combination of side scan and standard down looking. Quite often you see the same school in both views. The side scan view has the boat at top center and new info enters the top of the screen and rolls down falling off the bottom. At the scroll speed I am using it is 60 seconds top to bottom. So at 3 knots it is about 250 feet of boat travel while something scrolls from top to bottom. The down looking moves as a traditional fish finder. It has a 200 and an 83 KHz transducer, both in use in my images. Because of the smaller portion of the screen I assigned to it, that image moves across the screen in about 40 seconds. It is not obvious at first how the side scan image is portrayed. It is as though a flashlight was at the transducer shining out to the side, but the picture shown is not what you would see if your eye was at the transducer but it is as though you were looking straight down on the scene from the sky. A rise in the bottom shows bright and a hole is dark, a piling just shows a bright spot as the top with a long shadow behind it. It is that shallow angle of the illumination that makes light and dark areas that make up the "picture". But looking straight down or even out to about 45 degrees the bottom would just look all the same, bright with no shadows for contrast, so instead of making it all white, the unit displays that area as dark but it does display fish above that bottom. So that black stripe down the chart is about as wide as the water depth. If you are in 50 feet of water and the width of side scan view is 100 feet the line would be about half way out between the boat and the edge. And you would see the bottom from 50 feet away from the boat out to 100 feet away. Picture 01 Is debris under South River Bridge, a typical shot with full screen display of the side scan. Those are bridge supports at edges of picture. The right side of all the images is overexposed compared to the left. Humminbird is sending a new transducer. Picture 02 and 03 are of rock shoring of Thomas Point Light house. That is a full screen of just right side scan. Boat in upper left of picture. 04 and 05 are Bulkhead and sand bar from right and are right side scans also. The rest are combo view with the down looking as the left 1/3 of the screen, all taken between Thomas Point light and Bloody Point. 06, 07, 08 and 09 are shots where small schools show up in both views. In 09 the school upper most on left side goes all the way to the bottom since it touches its shadow. It is probably 60 feet to left of boat. The one closer to the center line is the one the down looking is marking. The upper of the two bright schools on the right side is 60 feet to the right but up higher, like only half way down since it is casting a shadow all the way out at 110 feet to the right. (I never realized bait fish stayed in such tight little well defined balls as this) Quite often as in 10, 11, and 12 the side scan will see schools that are too far out for the down looking to see. It might be worth turning a little to try and bring the way back lines over something 20 or 30 feet to the side. In 13 the school is 100 feet long in direction of travel and extends 100 feet on either side of boat but they must be a little bit scattered since the down looking didn't register red for strong return. The next one 14 returned a stronger signal on down looking but the school is only 30 feet long and 20 feet wide. It just happened to be tightly clumped together under the boat. The side scan seems to display something right under the boat as split in half. It seems like there should be conclusions that can be drawn from looking at the shape and density of school images like: Are scattered ill formed schools a different species than the small tight balls? Are scattered ill formed schools a result of just being chased? 15 is a picture of a nav screen showing where a particular screen shot/waypoint was saved. Transducer adjustment caused depth reading error at speed. |