A fire drill with Sonar, Down images.....(Pic Heavy)

[Shark]

I don't understand one bit of your high tech talk. I think I need an on the water demo. Say about 4 plus hours worth of demo and I'll bring my rods for hands on training too. lmao

Just kidding about not understanding.

Great info and thanks for showing us the snap shots.

 

[Triton Mike]

nwright - 8/3/2010 12:26 PM

Something doesn’t look right on the split screen sonar images. The 83khz has a wider cone angle than the 200khz and therefore should show more of the bottom. In your images they show the same bottom coverage. Also, the 200khz is supposed to give better definition than the 83khz but in your examples the opposite is true. ????

Good observation.. The 200khz beam has a 20 degree cone. So at 30ft deep it only covers 10ft of the bottom. the 83khz/60 degree cone covers 30ft circle at 30ft. A good percentage of those fish are suspended throughout the 15ft range (I'm rounding this # off for simple math). So your looking at a 5ft cone with the 200khz/20 degree beam.. So obviously there aren't as many fish in the 200khz 20 degree cone as there are in the 83khz/60 degree cone.

I use the 200khz beam for 2 reasons.
1. I get the most accurate GPS waypoints. Narrower beam is more accurate than a wider beam
2. It tells me exactly what fish are directly under the boat and near my spoon (if I see the spoon on the 200khz/20 degree beam side of the sonar split screen).

Essentially the 200khz beam is geared towards bottom detail and fish hidden in bottom cover. 83khz beam is made more for fish/bait due to it's bigger coverage range.

To make this even clearer and to show you a cool feature. The fish ID in orange are in the 20/200khz degree cone. The fish in blue are in the 83khz/40 degree cone.

 

[Biofisher I]

Great job. I'm sorry I have missed any of your prior post. Lot's of great detail and info. Keep up the good work.

 

[nwright]

Triton Mike - 8/3/2010 4:51 PM

nwright - 8/3/2010 12:26 PM

Something doesn’t look right on the split screen sonar images. The 83khz has a wider cone angle than the 200khz and therefore should show more of the bottom. In your images they show the same bottom coverage. Also, the 200khz is supposed to give better definition than the 83khz but in your examples the opposite is true. ????

I use the 200khz beam for 2 reasons.
1. I get the most accurate GPS waypoints. Narrower beam is more accurate than a wider beam

The cone angle has nothing to do with waypoint accuracy. The waypoint is based upon the HDOP (horizontal dilution of precision) not the vertical. Basically the GPS is marking the waypoint on top of the water, not in the water column.

 

[Triton Mike]

You are correct beam angle has ZERO to do with GPS accuracy.. but if your seeing the underwater tree on your sonar using the 83khz which could be 15ft to the right of your boat then is not DIRECTLY over the tree and thus not an accurate GPS point. If you see the tree on your 200khz ie narrow beam on your sonar that puts you closer to the exact location of the tree.

Look at this diagram of two different trees. Both you would see on your dual beam. If you dropped your spoon directly under the boat which tree would you hit? 200khz beam and not the 83khz right???? Have you ever fished a tree on your sonar and not hit the tree with your spoon? I have tons of times on dual beam. Never on 200khz narrow 20 degree beam.. So if you want the most accurate GPS point of the structure/cover you are trying to fish vertically 200khz will get you the most accurate GPS waypoint... Hope that clarifies..

 

[nwright]

"So if you want the most accurate GPS point of the structure/cover you are trying to fish vertically 200khz will get you the most accurate GPS waypoint... Hope that clarifies.. "

All you have to do is move your 2D cursor over the object (tree) you want to mark and save your waypoint. It doesn't matter which transducer you are using, the results will be the same As you move the cursor from your present boat position the GPS will add to or subtract from your present position to mark the waypoint.

In theory it would be easier to find and mark an object using a wider cone angle. Once located and a waypoint added, it would be better to vertical fish it with a narrow cone angle transducer. I would assume that is what you are trying to say.

 

[Triton Mike]

nwright, If you have two trees 30ft apart in 30ft of water and you go in between them. BOTH show up on your Sonar screen in 200/83 dual beam mode and NONE of them show up on the narrow 200/20 degree beam. How do you know which tree your marking the left one or the right one if they both show up on your sonar screen???? Technically, You can't tell left and right with SONAR alone with structure. Now with SI that's a different story move the cursor over to the structure and mark the way point and your done, but we are talking sonar here not SI. If you see the trees on the narrow 200khz/20 degree beam you cut your accuracy from a possible 15ft off on your waypoint to within 5ft in 30ft of water ie better accuracy.

nwright - 8/4/2010 5:56 AM

In theory it would be easier to find and mark an object using a wider cone angle. Once located and a waypoint added, it would be better to vertical fish it with a narrow cone angle transducer. I would assume that is what you are trying to say.

Not really. You are right to FIND the structure wide cone angle would be best. But from a waypoint accuracy standpoint. I would double back in the narrow beam and find the tree and key in on it for better accuracy. GPS points are only as accurate as how close you are to the structure being DIRECTLY under the boat. With wide beam the structure/tree CAN be off to the side as much as 15ft in 30ft of water. So if you follow your theory and mark the tree with the wide beam mode, you MIGHT not even see the structure on your narrow beam mode when you go to fish it because your tree can be off to the side of the boat. Now for some 15ft off is acceptable accuracy. But I look at it like this. If I am fishing a lay down with a bass in it and I cast 15ft to the side of the lay down the odds of me catching that bass aren't as good as if I casted 5ft from the lay down.

Take a look at these 2 images to compare the accuracy based on what you SEE on your sonar screen.. the RED X marks the way point based on the boat position (directly under the boat).. Technically the red x's should be directly where the boat is not on the lake bottom where I have it but just shows what I am saying to get my point across..


Both trees show up on sonar screen using wide beam (tree is a possible 15ft to the side of the boat). Neither tree shows up on narrow 20 degree beam..

Tree show up on narrow beam directly under the boat (within 5ft)..

Mike

 

[nwright]

"So if you follow your theory and mark the tree with the wide beam mode, you MIGHT not even see the structure on your narrow beam mode when you go to fish it because your tree can be off to the side of the boat. Now for some 15ft off is acceptable accuracy."

Mike, I like the images you have posted and they could be helpful to a lot of people. I question some of the things you have posted at the risk of being called "Fishton"!! With a Lowrance 2D sonar I can mark any tree that shows up on an 83 or 200Khz by moving the cursor over any tree, save a waypoint and go back to it with the 20 degree transducer. I do not have to be directly over it to mark it. I works just like structurescan/sidescan. I have done this several times with as much accuracy as if I had been directly over it.

 

[Triton Mike]

nw, I have no problem with agreeing to disagree here. By all means if your system works for you then don't change a thing. I Hope your having a great summer season..

Mike

 

[Doug V]

Not wanting to start a war here but there are several things you have to consider. GPS Accuracy is controlled by the number of satellites and correction signals HDOP and EPE are values that state the accuracy level. But What Mike was trying to point out is marking a waypoint on 2D sonar screen and coverage area. THe smaller the coverage area the less area in each sonar ping or Column of Pixels. Remember a screen is made up of numerous pixels rows and columns. Columns are vertical and rows are horizontal. When the sonar pings it fills in the column with the data returned from a selected area. 20° is a smaller area of data being displayed versus 60° data. Like Mike has shown in the 2D illustrations. When you move the cursor over the point of interest you want to make in 2D Screen and with Humminbird you can mark the points of interest and it will mark anything being displayed on the 2D Screen. If running in the 20° Cone the waypoint is going to be more precise because of the smaller coverage area versus a wider cone for that Ping or Column of Pixels being displayed your marking the Column of the data not the area that was recorded by the sonar. So in 30 feet each column in 20° is recording 10' of bottom coverage and at 15' is only covering 5' on that same column of pixels or ping. With 60° that coverage goes to 30' of bottom and 15' of coverage.

The only way to tell in Traditional 2D Sonar where something is at by the strength of return but this mainly works on fish for each single ping of sonar. Unless you use something like Humminbirds Quadrabeam Sonar that covers to the right and left two seperate beams then you can tell which side. Same thing goes with Down Imaging and Side Imaging. DownImaging is blending of data from all directions. Side Imaging shows exactly which direction it is.

With Humminbird you can view the 20° and 60° data separately in a split screen and can mark data from either cone but you can't tell with that Column of Data if it was front, back, left or right of the transducer. So the only way to get more precision is with narrower cone angle. And with Humminbirds Switchfire Clear Mode this is even more precise because it does not listen for the weaker returns in the side lobes of sonar....

Clear as Mud???

 

[nwright]

Doug V - 8/5/2010 2:37 PM

Not wanting to start a war here but there are several things you have to consider. GPS Accuracy is controlled by the number of satellites and correction signals HDOP and EPE are values that state the accuracy level. But What Mike was trying to point out is marking a waypoint on 2D sonar screen and coverage area. THe smaller the coverage area the less area in each sonar ping or Column of Pixels. Remember a screen is made up of numerous pixels rows and columns. Columns are vertical and rows are horizontal. When the sonar pings it fills in the column with the data returned from a selected area. 20° is a smaller area of data being displayed versus 60° data. Like Mike has shown in the 2D illustrations. When you move the cursor over the point of interest you want to make in 2D Screen and with Humminbird you can mark the points of interest and it will mark anything being displayed on the 2D Screen. If running in the 20° Cone the waypoint is going to be more precise because of the smaller coverage area versus a wider cone for that Ping or Column of Pixels being displayed your marking the Column of the data not the area that was recorded by the sonar. So in 30 feet each column in 20° is recording 10' of bottom coverage and at 15' is only covering 5' on that same column of pixels or ping. With 60° that coverage goes to 30' of bottom and 15' of coverage.

The only way to tell in Traditional 2D Sonar where something is at by the strength of return but this mainly works on fish for each single ping of sonar. Unless you use something like Humminbirds Quadrabeam Sonar that covers to the right and left two seperate beams then you can tell which side. Same thing goes with Down Imaging and Side Imaging. DownImaging is blending of data from all directions. Side Imaging shows exactly which direction it is.

With Humminbird you can view the 20° and 60° data separately in a split screen and can mark data from either cone but you can't tell with that Column of Data if it was front, back, left or right of the transducer. So the only way to get more precision is with narrower cone angle. And with Humminbirds Switchfire Clear Mode this is even more precise because it does not listen for the weaker returns in the side lobes of sonar....

Clear as Mud???

Well Doug, I'm surprised it took you this long to respond to this since the two of you are in lock-step on BBC.

As for GPS accuracy I hope your unit is more accurate than the EPE numbers your unit displays. Typically, a GPS is much more accurate than the EPE.

Using the logic both of you are using then waypoints derived from sidescan objects are way off and you have a hard time locating them. I never have had a problem marking an object 30, 40, 50ft, etc from the boat and being able to navigate the boat back on top of it. As for where an object is in relation to the boat using 2D sonar, I could care less. I can move my cursor over that object to create a waypoint. I can then go back to that object without any problem. If I want to know at any time how far and what direction the waypoint is from the boat I can use the navigate feature. I use overlay data, distance to destination along with a steer arrow to provide that info. I then know in real time the distance I am from that object, in feet, at all times.

I have enjoyed the exchange.

 

[Doug V]

Thanks for the kind comments...I'm here to help others learn and how to use all the feature of their Humminbirds But concerned your posts are contradicting yourself. Because you are telling that you can Mark Objects in 2D Sonar and that is what the subject has been on

nwright - 8/4/2010 6:50 PM

" With a Lowrance 2D sonar I can mark any tree that shows up on an 83 or 200Khz by moving the cursor over any tree, save a waypoint and go back to it with the 20 degree transducer. I do not have to be directly over it to mark it. I works just like structurescan/sidescan. I have done this several times with as much accuracy as if I had been directly over it.

Now last night you said...

nwright - 8/5/2010 10:53 PM


As for where an object is in relation to the boat using 2D sonar, I could care less. I can move my cursor over that object to create a waypoint. I can then go back to that object without any problem.

The topic of discussion is 2D Sonar and GPS Accuracy.

Triton Mike - 8/3/2010 4:51 PM

I use the 200khz beam for 2 reasons.
1. I get the most accurate GPS waypoints. Narrower beam is more accurate than a wider beam
2. It tells me exactly what fish are directly under the boat and near my spoon (if I see the spoon on the 200khz/20 degree beam side of the sonar split screen).

And you stated

nwright - 8/3/2010 7:50 PM

The cone angle has nothing to do with waypoint accuracy. The waypoint is based upon the HDOP (horizontal dilution of precision) not the vertical. Basically the GPS is marking the waypoint on top of the water, not in the water column.

Now if you want to discuss Side Imaging and Down Imaging and how GPS Works with these systems we can go into discussing Humminbird system of marking waypoints in SI or DI Views. It look like that is maybe what you are asking for???

nwright - 8/5/2010 10:53 PM


Using the logic both of you are using then waypoints derived from sidescan objects are way off and you have a hard time locating them. I never have had a problem marking an object 30, 40, 50ft, etc from the boat and being able to navigate the boat back on top of it.

We are discussing 2 different systems 2D - GPS Marking and SI/DI - GPS Marking. Each has different features and how the technology works.

If you can let me know which system you would like to discuss we can concentrate on that one then we can get into the other one if you would like.

 

[SpurHunter]

This essentialy has shown me I have no idea how to use a good depthfinder.
I am lost with all huge amount of info that has been posted here, you guys have been great! I will mark this thread and read it a few times, maybe I can figure some of it out.

 

[Doug V]

This brings up a good subject for more video clips to help others understand how the GPS and Sonar Systems work in unison. Got it on my list of Videos to do. Since GPS Marking capabilities are different for different sonar systems it will help that the user understands how and what he is marking and more importantly getting back to catch the fish you found.

I've got several help videos that show features of the Humminbird Product on my YouTube Channel over 30 different Videos and growing because of Ideas I get from questions asked on forums and seminars I conduct.
Here's My YouTube Channel: http://www.youtube.com/user/imonbass

 

[SpurHunter]

THat is a great idea. I need to look and see if I can ifnd a model like mine on the tube. I have a Garmin 178C. Cant bring myself to get a Side Scan that is worth more $$ than my boat is!

 

[Triton Mike]

SpurHunter - 8/6/2010 12:13 PM

Cant bring myself to get a Side Scan that is worth more $$ than my boat is!

IF it makes ya feel any better Spurhunter I had a 997SI on a electric only jon boat LOL emoPoke emoPoke

 

[SpurHunter]

But at least your boat doesnt look like its about to fall apart! emoLaugh emoLaugh

 

[nwright]

Doug, I haven't contradicted myself at all. I initially questioned Mike's 83/200 split image becaused both images showed the same bottom coverage. The 83khz also showed better definition which is the opposite of what they should show .Mike said " . I get the most accurate GPS waypoints. Narrower beam is more accurate than a wider beam ". I questioned this statement because I can mark an object using either transducer with the same accuracy and that the cone angle had nothing to do with GPS accuracy.

As for comparing Humminbird with any other unit---I could care less. All of them can do the job intended and how well they perform is directional proportional to the skill of the person using them.

 

[Triton Mike]

nwright, Not to be argumentative but since your a fan of our buddy Fishton (Lowrance guy) even he agrees on the 200 khz beam being more accurate via GPS. He supposingly runs a sonar school, if that gives him any credibility. Here is an excerpt from one of his posts that he made
.

 

[SS810]

emoThumbsup emoWorthy