In this video I did from a recent trip to the lake with my Humminbird Onix 10 SI, I was scanning the lake for Eel Grass. I’ll explain to you what Eel Grass looks like and what to look for when scanning the lake bottom for it.
In an earlier blog I wrote about needing Side image to get the most out of your Down Image scanning. In this blog I’ll show you an example when you needed Down Image to find the structure that is hard to see with the Side Imaging transducer. In this scan I am using my Humminbird Onix 10 Touch SI/DI unit. Then as usual I convert the recordings using ReefMaster Sonar Viewer software. In this blog I will only be posting three images and you can see why you still need both your Side Imaging and down Imaging transducer at the same time in most cases.
In most instances I use only my Side Imaging while scanning for structure and I use my Down Imaging to try and locate fish whether it’s bass, crappie, white bass or any other species of fish i might be after on that trip. When I’m scanning for structure with my Side Image I usually have my unit scanning out to 100 feet on each side. If I’m looking for fish with my Side Image and Down Image together I set the Side image range to either 50 or 60 feet. On my Side image I use the 455 kHz and on the Down Image I set it up to use the 800 kHz settings. This will usually give me the clearest images i have found on my units.
The color palette will be a matter of personal preference. On my Onix for example before all the software updates I liked to use the “Green” palette but with the last software update I find myself using the #2 “Amber” palette the most. On my 360 transducer in shallow water I like the “Gray” palette the best. As usual you will have the continually make changes on the fly with your “Sensitivity” and your “Contrast” setting during the scanning process.
Okay now for my first image from a recent scan I did on the water. I,n the image below you can see a lot of stuff in the water, there are lots of schools of bait-fish. You can see some larger fish near the bottom which could be catfish or Asian Carp. You can the edge on the old creek channel bank on the right side of the image. You can see some larger fish up in the water column under the bait-fish which could be bass, stripe or crappie. You can see what looks to be a tree limb on the lower left of the image and possibly a brush top almost in the center of the screen.
Now in the next image I am using the Down Image transducer to run the exact as area, as a matter of fact I was running both the Side Image and the Down Image at the same time to get this scan. But you can now see what I missed with just the Side Image transducer.
Wow, now what do you see in the Down Image scan? You can now clearly see the three big man-made brush tops someone dropped in the lake! You can still see the bait-fish and a few fish but not everything you saw in the Side Image scan image.
And finally in this last image I’l show you them side by side and see what you can and can’t see if you were only running one without the other.
Remember I was running both at the same time over the exact same area and I would have missed the three big brush tops without having them both on at the same time. So you can clearly see you need to run both at the same time to get the most out of your units. This is one reason you need the larger units like the 10″ or 12″ for the largest screen area you can see at once. I also run a Helix 12 SI Mega but most of the time I only use it for mapping as i find my Onix unit gives me the clearest image of the both of them.
I hope you get a little more understanding out of your expense tools you have added to you boat.
Definition of thermocline
: the region in a thermally stratified body of water which separates warmer surface water from cold deep water and in which temperature decreases rapidly with depth.
The thermocline is formed on lakes with little to no current flow that allows the mixing of the top and bottom layers of the lake waters. Since cold air and water is heavier that warm or hot air or water the heavier sinks and the warmer rises. In the following three images you can clear see the thermocline. Summer and early fall is the times that the thermocline is most prevalent with the high air temperatures this time of the year.
Why knowing where the thermocline is important to you as a fisherman? Simple it will define the maximum depth you need to be fishing. The thermocline is void of life giving oxygen so the fish you are seeking can not live in the thermocline. During the summer and early fall, adjust your unit to see the thermocline. Scan the area you are planning to fish and look for the top of the thermocline. Let’s say the top is at 27 feet as in the images in this blog. Then the maximum depth you need to fish is no deeper that 27 feet. Look for a or drop-off, shell mound or hump that is shallower than 27 feet and fish there if you see fish on them with your down image units.
Finding the thermocline is easy with the new Side Image and Down Image sonar units, in my case I use the Humminbird Onix 10 SI and the Helix 12 Gen2 Mega Scan. You will need to learn to adjust the sensitivity and contrast settings. You can find settings on this blog just do a search in the search bar. There are a lot of YouTube videos on how to tune your units.
Hope you find this blog helpful in understanding the thermocline in your fishing.
Wilson Lake, Florence, Alabama.
When Wilson Lake was impounded there was a lot of old structures, canal, bridges and other structure let on the lake floor. With the advent of the new sonar technology such as Side Imaging and Down Imaging you can still find a lot of them.
I have both Humminbird Onix and Helix Mega Scan units on my boat. These amazing pieces of technology enable me to see what’s still laying on the ;lake floor to this day almost a 100 years later!
A Little History on the Lake
Wilson Dam spans the Tennessee River between Florence (north) and Muscle Shoals (south), Alabama. It stands at an elevation of 508 feet and crosses the Tennessee on a 20-foot roadway along the top of the dam. Impoundment of the Tennessee River above Wilson Dam has created Wilson Lake, with a maximum width of 1.6 miles and a main shoreline of 154 miles.
Wilson Dam was erected by the Army Corps of Engineers in 1918-25 and turned over to the Tennessee Valley Authority when that agency was established in 1933. Wilson is a concrete gravity-dam on a blue limestone rock foundation. The total length of the structure is 4,535 feet, the height 137 feet, and the maximum width at the base (Including the apron) is 160 feet. The head the water depth on the upper side of the dam is 97.6 feet. There were originally 58 spillway gates in the face of the dam, each capable of discharging 10,000 cubic feet of water per second.
As I scan the lake bottom with my Side Image and Down Image units I’m always looking for objects that are on the lake bottom. If I do manage to find something, if I can I’ll research and see if I can find out what it is and if possible try to find a photo of what the object is or was. In the two photos below I found an old submerged arched bridge crossing a small stream or creek bed. You can clearly see the creek bed in the Side Image photo.
Click on the photo thumbnails to get a larger view.
I found an old submerged mill a couple of years ago that an old time fisherman told me if I had ever looked for it. In the two photos below you can see what the mill looked like before it was torn down and all that was left was the stone work of the mill.
The following photo is an old marina boat cover slips that instead of being torn down was easier to just pull it out into the lake and sink it. The tin metal top and sides are still on the old boat cover slips. I have tried to find a photo of the original one but have not been able to do so.
In this blog I’ll be discussing Side Imaging Sonar and Down Imaging and do you need it. As I discussed in my earlier blog on Sonar versus Down Imaging was it really needed. From the images I’ll post below we can see that some of the structure is visible in the Sonar and the Down Image views but the problem is where they are located in relation to the boat.
As stated in the earlier blog I will be converting recordings done with my Humminbird Onix 10 SI Touch and my Helix 12 Gen 2 Mega Scan SI units. The software I use to view the recording is ReefMaster Viewer and sometime I will use Deepview FV as well as AutoChart Pro. Three of these are purchased software and the other one is a free software version. You can do a Google search to find out more on these products. As for recording with your Humminbird unit I have a blog discussing this as well just follow this link “Recording”.
The problem with Sonar and Down Imaging while fishing or even scanning the lake bottom with your units. Is to determine where the structure is in relation to your boat. Since we are dealing with a 2 dimensional flat screen and scanning a 3 dimensional world. Since the software on the units is only placing pixel dots on the screen there is no way to show the bottom in a real world display. That is unless we are using Side Imaging.
With Sonar and Down Imaging as we drive over the structure is it under the boat as the display shows? It possibly could be and we can tell this with the Sonar view by looking at the colors displayed on the screen palette. Since on a Sonar transducer set to 200 kHz the cone angle is pointing straight down and for an example shining like a flashlight beam. Take a flashlight and turn it on and point it straight down at the floor. The circle of light you see will represent the transducers cone angle. As you can see the angle is in a circular pattern and any object that enters the cone will be visible. Now lower the flashlight down towards the floor and you will see the circle of light gets smaller. This represents the depth of the water your boat is setting in. With a standard 200 kHz transducer the circle will be 1/3 of the depth of the water, for example in nine feet of water you will only be scanning a three foot circle of the bottom. Now move out into 30 feet of water and now you will be looking at a ten foot circle of the bottom.
With all that being said if your boat is in 9 feet of water and you drive your boat over say a stump, and it shows up on the display screen then that stump is directly under the boat. That is under the transducer where ever it is located.
Now let’s say we dropped a waypoint on that stump and wanted to fish it. As we turn the boat around and go back to the waypoint where is the stump in relation to the boat. Again on the display as we get closer to it it will show up on the display but now is it under the boat or in front, rear or right or left of the boat?
The only true way to know for sure is either with the Side Image or the Humminbird 360* transducer. With the Side Image transducer the problem is we now have to drive past the stump to see it displayed on the unit. But now we will know if the stump is on the right side or the left side of the boat. With the Humminbird 360* transducer we can see the stump without having to even move the boat. If the stump is at a three o’clock position we just cast to the stump at a 90* angle to find the stump.
I hope this explains a little the advantage of the Side Image transducer. Take a look at the images below to see what I am trying to explain. I’ll do a blog on the Humminbird 360* transducer after I get on the water and do some screen shots with it.
Click on the Thumbnails for an Enlarged view of the images.
In this image we can see a stump displayed on the Sonar but only know it is located slightly to the right of the boat by looking at the Side Image view. In this view we see the top is directly under the boat and slightly behind the boat.
Now let’s look at this gravel point that is off the the right side of the boat. Without the Side Image view we would not even know it was there.Can you see the gravel bar on both sides of the boat in the Down Image view.
See the tree top slightly to the left side but still under the boat?Stump field to the right and a stake-bed to the left not visible on the Down Image view.
I get asked sometimes if Down Image is really worth the extra expense over the regular Sonar units. I definitely have to say yes but only if you do not know what your looking at with the Sonar unit. I’ve used sonar units since the old flashers and paper graphs from back in the mid to late seventies. One thing for sure is that you want to get one with a GPS so you can return to the structure that you will find with them.
My units are Humminbird Onix 10 SI Touch and Helix 10 DI and a Helix 12 SI. All of these unit have GPS and Sonar built into them. I’ve also used a Garmin unit and Lowrance units with good results.
One thing I must say is that of all the Humminbird units that I have owned, everyone of them has had software issues and several have had to be returned to Humminbird for repairs! I don’t know why they can not get their software right before they release their products. Anytime that they have to release five to ten software updates that tells me they have issue with their software!
All of the images you will see in this article will be from recordings that I have recorded with either my Humminbird Onix or my Helix 12 units and then viewed in ReefMaster Viewer software.
I use the Sonar with the 83/200 kHz transducer settings and my chart speed is normally around 5 or 6 with my boat speed at about 3.5 to 4 mph when I’m doing the recordings.
Look at the images below and you will be able after a lot of time on the water looking at different structures to learn what you are really looking at. In my next blog I’ll show you the Side Images and the Down Images views.
Hope this helps you to learn your units a little better and catch a few more fish.
Click on the image thumbnails for a larger view of the images.
When you’re out on the water scanning with your down image you have the options of using the 455 kHz or 800 kHz setting on my Humminbird Onix. In the photos I’ll show you what you are missing if you are not using the correct setting. When you are in deep water you need different setting than when you are in shallow water. With the Humminbird Onix the 455 kHz setting is using two 86 kHz beams at once which covers 172 degrees. While the 800 kHz setting use two 55 degree beams that only cover 110 degrees total. So you can see that the narrower beam does not reach out as far as the wider 455 kHz setting.
With the 2D or sonar beam you have a choice of either the 20 degree or the 83 degree cone or a combination of both. You need to remember that with the 2D sonar cone set to 20 degrees you are only scanning 1/3 the depth of the water. In other words if you are in say 9 feet of water you are only looking at a 3 foot circle under your boat. With the 83 degree setting you are covering an equal area to your depth. If you are still in the 9 foot of water you are scanning a 9 foot circle under your boat. For the best scanning I’d suggest you a combination of both the 20 cone and the 83 degree cone.
Now let’s look at the photos a second. The photo above I have the setting set to 455 kHz with a wide beam selected. In this can I am in water that is less than 10 feet deep and you can see I can scan a very wide area out from my boat.
Now in this photo I have my unit set to 800 kHz with a beam wide setting which only covers 110 degrees out from both sides of the boat. I’m still in about 10 feet of water or less. As you can see you can’t see nearly as much detail as in the photo above set to 455 kHz.
Now let’s look at the down image scan while I’m scanning in water around 30 feet deep in the photo above. I have the unit set to 455 kHz and I’m covering 172 degrees under the boat. The fish by the way are stripe and shad. As you can see there are rocks close to the shore line.
Finally in the above photo I have the unit set to 800 kHz in 30 feet of water and scanning the exact same water and since I have a narrow 110 degree of coverage I can’t see the shoreline or the rocks near the shore. I can still see the stripe and the shad but in this case the 455 kHz gave me more detail than the 800 kHz setting.
Let’s wrap it up, the setting are really up to you and what depth water you are in. If you only have a Down Image unit the beams are different in that your choices are 455 kHz using a 75 degree cone angle and 800 kHz which only gives you a 45 degree cone angle which will not give you as much coverage as the side Image units. One recommendation I suggest is to set the Down Image to 800 kHz and the Side Image to 455 kHz while scanning so you don’t get the cross-talk if the transducer trying to pick them both up at once id you have them set to the same 455 or 800 kHz setting.
Hope this helps you better understand your unit better….
In this series of Side Image and Down Image scans I’m scanning an original creek channel in the back of Bear Creek on Pickwick Lake. While scanning I found an interesting object on the lake bottom.
This one will be of Objects Found.
Take a look at this side scan and see what you can find before looking at the photo below. As I showed you in the last Blog on Bottom Composition you can see the darker colors are a soft bottom in this case the original creek channel. And the brighter color is of the harder bottom composition. The shadows next to the objects lets you determine the height of the object on the lake bottom.
Photo 2 below…….
Now that you’ve had a chance to find the objects I’ll point out what you should have found. (1) is a false return as I was making a sharp turn with my boat so disregard it. (2) is a sunken tree top that either was placed there by another fisherman or washed into the creek and sank on its on. (3) is a very large stump that you can tell by the shadow it casts. (4) Finally as you can tell this is an old sunken boat. It looks to be a flat bottom boat without an outboard engine attached. The GPS coordinates of the area if you want to look at the objects to learn your unit is as follows.
GPS: N 34 48.113 – W088 05.365
Hope this helps you understand units.