Fish Finder Basics - www.ifish.net
The Oregonian's Bill Monroe!

Go Back   www.ifish.net > Ifish Fishing and Hunting > Tech Tips and Keepers

Reply
 
Thread Tools Search this Thread Display Modes
Old 05-11-2015, 06:54 AM   #1
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Fish Finder Basics

I'm recreating this post as some of my images from my last post have gone missing and that post was a reply to someone else's thread. Without having its own thread it was hard for people to find. I hope people find the info helpful.


Here is a very basic run down on how your sonar is working.

Your sonar is shooting sound waves down and as they reach impediments like fish or the bottom the sound wave bounces off that, the returning echo is registered by your FF and interrupted into a distance from the transducer.

For ease I'm going to call the shape that your fish finder emits a cone like Figure A. In reality your cone has lobes like shown in 2 dimensions in Figure B and a 3 dimensional representation in Figure C.



Again, for ease, lets just refer to it as a cone.

How Returns are displayed

Everything in your 3 dimensional cone is displayed in a 1 dimensional line based off distance from the transducer.

Figure D shows real life where all the fish are around the area of your cone.
Figure E shows real life fish at different depths
Figure F is what your fish finder shows you. Your fish finder measures the distance of each echo and displays it as dot on a line. Your fish finder doesn't care where in the cone the fish is, front, back, left, right. It just measures how far away it is and puts a dot on a line. This line is your "A scope", or amplitude scope.



An A scope is the same as...

...a flasher wheel, except it's straightened out into a line instead of a circle. Flasher wheels DO NOT tell you which direction fish are. They measure the distance from the transducer to the fish and display it in a circle.

The advantage of an A scope line over a flasher wheel is that you can log the history of your A scope and display it as a picture.

Your screen is history

Everything you see on your screen is history. It all happened in the past and is no longer under your boat.



In this image:
A. The boat is traveling
B. All the fish you are looking at on the screen are long gone.
C. Gone out of your cone.
D. Yep these are gone also.
E. The A scope, the only true indicator of what is under your boat right now, shows fish at 24, 25, 27, 30 and 33 feet away from your transducer.


Q. What are arches and how are they made?

Arches

To explain this lets say the fish is in 15 feet of water and just entered the cone at letter "D" below.




Even though the fish is in 15 feet of water the FF is not measuring that. It is measuring how far the fish is from the transducer. So the distance from point "O" to point "D" is about 17'. So, your FF displays the first marks at a depth of 17'

As the fish passes through the cone to point "C" it is still in 15' of water but since it is in a different portion of the cone, it is actually closer to the transducer, Point "O" to point "C". This causes the visible return displayed by the FF to move up slightly to 15'.

As the fish passes out of the cone the distance between the transducer and the fish grows. Now the distance is back to about 17'. The returns on the fish finder indicate this growing distance and an arch is formed.

Streaks


A streak starts just the same as a arch. The fish enters at the outside of the cone. Now if a fish swims along the same direction as the boat is traveling and at a similar pace, then the FF will read the distance from the transducer to the fish and give a return at that distance. If the fish stays with the boat for 5 seconds then you will receive a 5 second long streak. If the fish stays with the boat for 30 seconds, a 30 second steak.

Lets say you are anchored up sturgeon fishing and a sturgeon is hovering 1' off the bottom in your cone. You can see a streak like that for a very long time until it moves on.

Squiggles

If a fish swims into your cone and travels the same direction as you, but meanders within the cone. Varying it's distance from the transducer. For instance maybe it swims right under the boat for 30 seconds then veers off to the edge of the cone but doesn't leave the cone, then veers back under the boat. This will give a return that starts close to the transducer, appears to go deeper, then shallower again.

So applying all this information to some pictures.


On the far left of this screen shot it looked like it was a cross section of a seal.

This wouldn't be a cross section of a seal(even though it does LOOK like a center mass with fins), as a FF doesn't take pictures that way. Often times looking at the history scrolling out can seem like images but in reality that's not the way it works.

This large image was on the outskirts of the cone and returning a week signal, then came more closely into your cone and as it did so came closer to the transducer, hence the arch, then passed out of your cone, again returning a week return. Depending on your tuning of your FF this could be something very big or it could be a tight school of bait fish.



This is most definitely a school of fish that passed through your cone and where in your cone for a while. Hence a more streaky looking return, indicating that they stayed in the cone for a longer time.



At 20' of water, depending on what angle you have your cone set to these are most definitely fish and more then likely were directly under your boat.
At 20 feet the diameter of your cone on the bottom is very narrow.



In 20 feet of water a 200kHZ 20 degree cone would be about 7' in diameter on the bottom and a 83kHZ 60 degree angle wider cone would be about 23' in diameter on the bottom.

That is the very very basics of fish finder interpretations. If you have any questions or want to post some FF screen shots for interpretation please do so. I'm happy to answer questions via PM also.

__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 05-11-2015, 06:54 AM   #2
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Down Imaging Explained

Down imaging is a narrow beam that runs right to left and displays detailed imaging that is laid out in the same orientation as normal sonar.


As you can see from the image above the down imaging beam divides your sonar cone in half and it slices the profile of what's in it's path and shows that information as a side view.


If this penny were standing on end on the bottom and you were traveling in the direction of the red arrow the down imaging would take a profile picture of the penny in slices, like the yellow lines, and display it like the first image below. If you were traveling the direction of the blue line the down imaging would only see the side of the penny and display it like the bottom image below.

So down imaging only gives you a profile of what is on the bottom based of the direction you are traveling. It is a highly accurate and very detailed profile, but still only a profile.
It's also worth noting that down imaging does not extend out like side imaging does. It more or less mirrors the width and angle of your standard sonar cone.

Here is an excellent image of the different shape a side imaging cone has versus a down imaging cone.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-11-2015, 06:55 AM   #3
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Side imaging explained.



Side imaging uses 2 WIDE beams, right and left, to give the viewer an aerial view of what the bottom looks like. It uses shading to help discern mild slopes, valleys, hills, and other contours. By far the most confusing part of side imaging is the black spacing in the center of the picture. I've included this video to help explain it.
Sorry but it's brand specific.
www.youtube.com/watch?v=yNucS1bniIw
So by comparison of the 3 types of sonar I'm talking about:
Standard sonar uses a round cone shape to gather lots of returns and convert them into a line and displays the information as a profile picture of what's under your boat
Down imaging uses a thin slice across the cone to give a more detailed image but it doesn't gather as much data as the more round cone, and then displays that as a profile picture of whats under your boat
Side imaging uses 2 WIDE thin cones to reach far to the sides and give a detailed aerial image of what is under and to the sides of your boat.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 05-11-2015, 07:18 AM   #4
Smj
King Salmon
 
Join Date: Aug 2000
Location: Portland OR.
Posts: 5,077
Default Re: Fish Finder Basics

Oh this'll be fun! I'm going to bring a screen shot I have and we'll see if you can tell me what is in it. Stay tuned.........




I've stared at this screen for what seems like hours. My neck hurts at times from being turned around so much.

Smj
__________________
Member# 332
Smj is offline   Reply With Quote
Old 05-11-2015, 08:48 AM   #5
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by Smj View Post
Oh this'll be fun! I'm going to bring a screen shot I have and we'll see if you can tell me what is in it. Stay tuned.........




I've stared at this screen for what seems like hours. My neck hurts at times from being turned around so much.

Smj
Some options:

You are bottom fishing and hooked something/somethings and somethings bigger took a seriously look at it.
OR
you were retrieving your gear and missed a couple fish. It looks like a weight and a bait or a lure being fairly rapidly retrieved.

You can see the bottom disturbance and sediment clouding up the image from 45 to 49 feet after the retrieval. That leads me to believe something was hooked, the other fish could have just been looking through the cloud for a free snack.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-11-2015, 08:50 AM   #6
The Lucky Duck
Tuna!
 
The Lucky Duck's Avatar
 
Join Date: Jun 2007
Location: Eugene
Posts: 1,877
Default Re: Fish Finder Basics

Quote:
Originally Posted by Smj View Post
Oh this'll be fun! I'm going to bring a screen shot I have and we'll see if you can tell me what is in it. Stay tuned.........
If your asking what this shot looks like? I would say you dropped a fairly heavy weight, maybe a spreader bar down on a rock or hard structure with a fish on it. It looks like you lifted the weight in a attempt to jig or free up.

Excellent thread, after you explain side image and down image I would share some info on 360 if anyone is interested. I won't have the cool diagrams that Likes has.



I've stared at this screen for what seems like hours. My neck hurts at times from being turned around so much.

Smj
The Lucky Duck is offline   Reply With Quote
Old 05-11-2015, 08:59 AM   #7
saltaddict
Chromer
 
Join Date: Mar 2012
Location: St. Helens
Posts: 756
Default Re: Fish Finder Basics

Great information. Thanks for taking the time to post.
saltaddict is offline   Reply With Quote
Old 05-11-2015, 09:00 AM   #8
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by Smj View Post
Oh this'll be fun! I'm going to bring a screen shot I have and we'll see if you can tell me what is in it. Stay tuned.........




I've stared at this screen for what seems like hours. My neck hurts at times from being turned around so much.

Smj

Quote:
Originally Posted by The Lucky Duck View Post
If your asking what this shot looks like? I would say you dropped a fairly heavy weight, maybe a spreader bar down on a rock or hard structure with a fish on it. It looks like you lifted the weight in a attempt to jig or free up.

Excellent thread, after you explain side image and down image I would share some info on 360 if anyone is interested. I won't have the cool diagrams that Likes has.
Unless it's an optical illusion that is coming up not going down. The first echo starts on the bottom then as the screen scrolls it comes up past the 38' mark.

I'd love to hear about your 360! I've been wondering how well it's working for you... but then I saw your Koke post and kinda figured it's probably not hurting your success. Haha
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-11-2015, 09:03 AM   #9
spey4steel
Steelhead
 
Join Date: Mar 2006
Posts: 136
Default Re: Fish Finder Basics

Thanks so much for this. I just recently saw the original post for the first time and found it very helpful but was wishing I could see all the images, so this is great. Very educational!
spey4steel is offline   Reply With Quote
Old 05-11-2015, 09:55 AM   #10
Chinook Angler
Chromer
 
Chinook Angler's Avatar
 
Join Date: Jun 2010
Location: PDX
Posts: 771
Default Re: Fish Finder Basics

An awesome thread! Thank you for taking time to post and explain all this stuff!
Chinook Angler is offline   Reply With Quote
Old 05-11-2015, 10:41 AM   #11
The Lucky Duck
Tuna!
 
The Lucky Duck's Avatar
 
Join Date: Jun 2007
Location: Eugene
Posts: 1,877
Default Re: Fish Finder Basics

Quote:
Originally Posted by The Likes View Post
Unless it's an optical illusion that is coming up not going down. The first echo starts on the bottom then as the screen scrolls it comes up past the 38' mark.

I'd love to hear about your 360! I've been wondering how well it's working for you... but then I saw your Koke post and kinda figured it's probably not hurting your success. Haha
You are absolutely right. Now I am stumped. Maybe 1 or even 2 jigs being worked by other rods?

The 360 has it's limitations but it is paying off BIG TIME this year. The kokanee are not settling on the bottom, where they are easy to target. So we are forced to chase schools, virtually impossible with conventional sonar.
The Lucky Duck is offline   Reply With Quote
Old 05-11-2015, 11:19 AM   #12
Tinman
 
Join Date: Aug 2000
Location: Portland & Oceanside, Oregon
Posts: 9,131
Default Re: Fish Finder Basics

Great illustration of A-Scope, which is one of the best features of fishfinders. As the man said, everything on the screen is history.
__________________
...helping you become the captain everyone trusts... https://www.theoceancoach.com/
Tinman is offline   Reply With Quote
Old 05-12-2015, 08:37 AM   #13
Smj
King Salmon
 
Join Date: Aug 2000
Location: Portland OR.
Posts: 5,077
Default Re: Fish Finder Basics

Quote:
Originally Posted by The Likes View Post
Some options:

You are bottom fishing and hooked something/somethings and somethings bigger took a seriously look at it.
OR
you were retrieving your gear and missed a couple fish. It looks like a weight and a bait or a lure being fairly rapidly retrieved.

You can see the bottom disturbance and sediment clouding up the image from 45 to 49 feet after the retrieval. That leads me to believe something was hooked, the other fish could have just been looking through the cloud for a free snack.


Pretty good! From staring at the screen when we were perch fishing at Woahink Lake I determined the following from staring at the screen for hours.

There is a fish being jerked from the bottom, deep water and mono line mean serious hook sets and quick reeling. The fact there is color to the vertical line indicates fish. The bait line and sinker went to the bottom and a perch grabbed it instantly. First line left, black, second line color.

The other relatively horizontal red/orange lines are fish milling around. I believe the excitement got them moving off bottom further. At times the fish come and check out our sinkers also. We run roughly 16"-18" leaders with bait on the bottom.

The dark black/blue horizontal lines to left and right are our sinker/bait as we lift/drop slightly.

On the bottom few inches are what I believe to be some kind of small shrimp that the perch feed on. When we look for a place to drop the anchor we'll see "Clouds" of these shrimp, sometimes coming up three feet from bottom. Where there's a cloud there will be fish.

And finally. I believe there is one perch that came up to 46' to checkout/eat the shrimp that the highly stressed perch on the hook lost. That perch ate some and returned to bottom while the rest of the hooked perch's lunch rose slowly.

These fish are feeding, gorging, on these shrimp. They look like shrimp as I've seen them, all over the boat. That's part of the reason we don't do Woahink that much due to the depth and the perch having the stomachs in their throats, and little shrimp all over the boat.

At this lake I can run my unit at max sensitivity, it's very clear. I also zoom in, very important to zoom to where you expect your quarry to be. There's no sense in viewing 0'-50' when we know we're going to fish the bottom. without being zoomed the picture in the my screen shot would be way different, with tiny little marks instead of the clear picture. Using my 640 pixels in 12' rather than 50' makes a huge difference!

Zoom to where you are fishing whether it be in a lake, the Harbor or the ocean. If you don't see fish, then change where you are fishing AND looking.

Smj
__________________
Member# 332
Smj is offline   Reply With Quote
Old 05-12-2015, 08:53 AM   #14
The Lucky Duck
Tuna!
 
The Lucky Duck's Avatar
 
Join Date: Jun 2007
Location: Eugene
Posts: 1,877
Default Re: Fish Finder Basics

Quote:
Originally Posted by Smj View Post


Pretty good! From staring at the screen when we were perch fishing at Woahink Lake I determined the following from staring at the screen for hours.

There is a fish being jerked from the bottom, deep water and mono line mean serious hook sets and quick reeling. The fact there is color to the vertical line indicates fish. The bait line and sinker went to the bottom and a perch grabbed it instantly. First line left, black, second line color.

The other relatively horizontal red/orange lines are fish milling around. I believe the excitement got them moving off bottom further. At times the fish come and check out our sinkers also. We run roughly 16"-18" leaders with bait on the bottom.

The dark black/blue horizontal lines to left and right are our sinker/bait as we lift/drop slightly.

On the bottom few inches are what I believe to be some kind of small shrimp that the perch feed on. When we look for a place to drop the anchor we'll see "Clouds" of these shrimp, sometimes coming up three feet from bottom. Where there's a cloud there will be fish.

And finally. I believe there is one perch that came up to 46' to checkout/eat the shrimp that the highly stressed perch on the hook lost. That perch ate some and returned to bottom while the rest of the hooked perch's lunch rose slowly.

These fish are feeding, gorging, on these shrimp. They look like shrimp as I've seen them, all over the boat. That's part of the reason we don't do Woahink that much due to the depth and the perch having the stomachs in their throats, and little shrimp all over the boat.

At this lake I can run my unit at max sensitivity, it's very clear. I also zoom in, very important to zoom to where you expect your quarry to be. There's no sense in viewing 0'-50' when we know we're going to fish the bottom. without being zoomed the picture in the my screen shot would be way different, with tiny little marks instead of the clear picture. Using my 640 pixels in 12' rather than 50' makes a huge difference!

Zoom to where you are fishing whether it be in a lake, the Harbor or the ocean. If you don't see fish, then change where you are fishing AND looking.

Smj
Excellent
The Lucky Duck is offline   Reply With Quote
Old 05-12-2015, 09:31 PM   #15
ccw
King Salmon
 
ccw's Avatar
 
Join Date: Feb 2010
Posts: 8,714
Default Re: Fish Finder Basics

I'd love to hear your interpretations:








CW
__________________
"To strive, to seek, to find and not to yield."

(from Ulysses - Tennyson, 1833)
ccw is offline   Reply With Quote
Old 05-12-2015, 11:29 PM   #16
xstreme357
Sturgeon
 
xstreme357's Avatar
 
Join Date: May 2005
Location: bg, wa
Posts: 4,032
Default Re: Fish Finder Basics

Great thread!! Do you know much about Raymarine's? If so if love to have you out to dial in my FF!! Lol
__________________
Ifish; turning yesterday's noobs, into tomorrow's guides!
xstreme357 is offline   Reply With Quote
Old 05-13-2015, 07:24 AM   #17
Beach Caster
Steelhead
 
Beach Caster's Avatar
 
Join Date: Mar 2001
Location: Seattle, WA
Posts: 270
Default

Here's a couple off of the Dragonfly from the big C this spring. Pic 1: two springers traveling tight together on the bottom or the same fish moving up and down in the cone?
Attached Thumbnails
Click image for larger version

Name:	20150329_165940_1431526529861.jpg
Views:	2128
Size:	31.8 KB
ID:	333338   Click image for larger version

Name:	20150329_113459_1431526572457.jpg
Views:	2084
Size:	30.8 KB
ID:	333346  
Beach Caster is offline   Reply With Quote
Old 05-13-2015, 07:34 AM   #18
artc1688
Steelhead
 
Join Date: Sep 2014
Location: Portland, OR
Posts: 461
Default Re: Fish Finder Basics

Great insight and got me start thinking (don't do that often - according to my wife)...

why not invent a "connected" fish finder that allows multiple fish finders to be connected.... capable of plotting out a larger map on what is coming/going.
artc1688 is offline   Reply With Quote
Old 05-13-2015, 09:04 AM   #19
Smj
King Salmon
 
Join Date: Aug 2000
Location: Portland OR.
Posts: 5,077
Default Re: Fish Finder Basics

CCW...

First pic...It really helps to know what conditions are. You could get a pick like that out of a sterile lake with some flotsam in the water. You could be looking at a fish or three, and some flotsam in the water. Zooming in will show the arc of a mark better, better indication of a fish. Also, moving boat/water or anchored?

Second pic....I'd say flotsam, fish would have orange/red in a mark that size. I'm assuming you have the finder set the same? You could, I suppose, adjust it to show fish marks that color? I looks like on the far right your lure/bait hanging straight down. Were you anchored in #2? The marks being flat lines look like it.
Not so much need for zoom in the shallow water, but if I were fishing in water that shallow for salmon I'd still zoom. We're pretty sure you don't need to be looking above 5'?

Pic three....You're either anchored or boat/water is moving very slow. slight wave action shown by the wavy pattern of the marks, and there's something rising slowly to the surface. The solid blue/black line near the bottom looks like your lure/lead/down rigger ball?

Question? Do YOU know what you're seeing on the screen? LOL I like the pictures your unit puts up, they're close to mine, and mine is ancient! My buddies ultra fancy $$$ unit doesn't have nearly the picture, or at least I've had trouble getting it.

Smj
__________________
Member# 332
Smj is offline   Reply With Quote
Old 05-13-2015, 09:12 AM   #20
Smj
King Salmon
 
Join Date: Aug 2000
Location: Portland OR.
Posts: 5,077
Default Re: Fish Finder Basics

Just noticed CCW, you're running at 200 KHZ? I believe 50 KHZ gives you a bigger cone, for water 100' or less?

Also noticed I missed pic four....I'd say a fish, for sure, came into the cone as it was returning to the bottom.

I don't see fish on my unit if they're within 6" of the bottom. What I'll see, because I'm zoomed, is a slight red on the bottom and the depth on the side shows different from the from the actual depth reading, by half a foot.

Smj
__________________
Member# 332
Smj is offline   Reply With Quote
Old 05-13-2015, 09:46 AM   #21
spare link
Tuna!
 
spare link's Avatar
 
Join Date: Jan 2003
Location: Sandy, OR
Posts: 1,876
Default Re: Fish Finder Basics

So what kind of setting are you guys running on your sonars? I get a lot of noise on mine but i feel if i up the noise reduction that it miss a lot.

I have messed with it quite a few times but it never looks right to me. I went fishing on a buddies boat a few weeks ago and he had a little older unit then i run and his screen was blank until a fish swam by and you could clearly see it. he did not have any noise on his screen.

I am running a Lowrance HDS 5.
__________________
Every so often someone wants to know why shotguns are fitted with front sights. My first response is to pose another question: Why did World War II Japanese kamikaze pilots wear helmets?
spare link is offline   Reply With Quote
Old 05-13-2015, 04:23 PM   #22
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by ccw View Post
I'd love to hear your interpretations:








CW
#1 a game fish on the far left in yellow, game fish on the bottom about 2/3 of the way across the screen. The first fish went through your cone a while ago. The rest of the marks are smaller fish. You can tell the yellow mark is larger because it's thicker, vertically, on the screen and given a yellow color which on your color palette is indicating more density. The other blue/red marks are fish just much smaller. Check your manual also to see what color is used for bottom separation. I believe that white line "in" the bottom is a separation line. Meaning your FF sees that return as being off the bottom but it happens to be the same distance as something else so it is using that to distinguish them apart.

#2 small fish that were in your cone for a long time. They could be swimming or you are traveling over the top of them slowly. Again the blue/red return on the ff indicating the diminutive nature of them. This could possibly be trolled gear but I don't think so.

#3 same as #2 but it was wavy water. You can see the bottom and the streaks moving up and down simultaneously. Then either the fish traveled up
in the water or you reeled in some gear that was trolled

#4 Large fish maybe two. Or a fish sitting on a log. If you had down imagining I would have been running it side by side. Also you don't have a speed displayed. Images like this one mean a lot more in context.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-13-2015, 04:30 PM   #23
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by spare link View Post
So what kind of setting are you guys running on your sonars? I get a lot of noise on mine but i feel if i up the noise reduction that it miss a lot.

I have messed with it quite a few times but it never looks right to me. I went fishing on a buddies boat a few weeks ago and he had a little older unit then i run and his screen was blank until a fish swam by and you could clearly see it. he did not have any noise on his screen.

I am running a Lowrance HDS 5.
The more you ask the FF to filter out information it thinks isn't important, the less information you get to decide if it's important. I like to have as much information as I can and I'll filter out my own info in my head.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-13-2015, 04:36 PM   #24
rollcast
Ifish Nate
 
rollcast's Avatar
 
Join Date: Oct 2002
Location: Portland (Cedar Mill)
Posts: 2,269
Default Re: Fish Finder Basics

Quote:
Originally Posted by The Likes View Post
The more you ask the FF to filter out information it thinks isn't important, the less information you get to decide if it's important. I like to have as much information as I can and I'll filter out my own info in my head.
+1 I want all the information and I will filter it out myself!
__________________
fish tremble when they hear my name

skunk is a fly, not an event
rollcast is offline   Reply With Quote
Old 05-13-2015, 04:41 PM   #25
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by Beach Caster View Post
Here's a couple off of the Dragonfly from the big C this spring. Pic 1: two springers traveling tight together on the bottom or the same fish moving up and down in the cone?
Sound travels at about 4800 feet per second through water. I know fish are fast but not fast enough to appear in two different places on a FF. It's 2 separate fish for sure.
Remember the only thing under your boat is what's displayed on the A scope. So if you have returns at different distances at the same time it can not be the same fish.

Quote:
Originally Posted by xstreme357 View Post
Great thread!! Do you know much about Raymarine's? If so if love to have you out to dial in my FF!! Lol
You paid for a nice machine my friend, spend some time on the water not fishing, just you and your FF getting to know each other.

Quote:
Originally Posted by artc1688 View Post
Great insight and got me start thinking (don't do that often - according to my wife)...

why not invent a "connected" fish finder that allows multiple fish finders to be connected.... capable of plotting out a larger map on what is coming/going.
People already run multiple FF, also there are horizontal FF, and sweeping side imaging machines. I believe Lucky Duck is going to post about his Hummingbird 360. That's going to be a great read. I've never seen one in action. Still though, FFers are tools, you have to know how to use your tool for it to be a benefit to you.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-13-2015, 08:31 PM   #26
Beach Caster
Steelhead
 
Beach Caster's Avatar
 
Join Date: Mar 2001
Location: Seattle, WA
Posts: 270
Default Re: Fish Finder Basics

Thanks TL. So what are the horizontal lines that appear at the top of my dragon fly screen pics? Propwash? Our fishing lines were on the bottom.

That appears to be a big fish that appears just two feet under the surface in my second pic?

One other question regarding the side profile of the bottom, is the image probing 6-8 feet into the bottom of the river and showing us whether its sand or rock? If so how can you tell which is which? Sometimes there are what appear to be logs under the sand 3-4 feet, can the down imaging actually tell me what's under the bottom 3-4 feet?

BC
__________________
Keep your hooks sharp!
Beach Caster
Beach Caster is offline   Reply With Quote
Old 05-13-2015, 09:14 PM   #27
P Stewart
Cutthroat
 
Join Date: Sep 2005
Location: Nehalem, OR
Posts: 38
Default Re: Fish Finder Basics

Great thread. I am learning my new fish finder this spring and appreciate all the great input. One thing I have a bit of trouble with is determining bottom structure, i.e. sand, mud, rocks etc. Do you have any tips for determining bottom composition?
__________________
Regards- Pat

"Every man's life, liberty, and property are in danger when the Legislature is in session."
Daniel Webster
P Stewart is offline   Reply With Quote
Old 05-14-2015, 06:34 AM   #28
The Lucky Duck
Tuna!
 
The Lucky Duck's Avatar
 
Join Date: Jun 2007
Location: Eugene
Posts: 1,877
Default Re: Fish Finder Basics

People already run multiple FF, also there are horizontal FF, and sweeping side imaging machines. I believe Lucky Duck is going to post about his Hummingbird 360. That's going to be a great read. I've never seen one in action. Still though, FFers are tools, you have to know how to use your tool for it to be a benefit to you.[/QUOTE]

TL, I have quite a bit of experience with "using" the 360, however you are THE MAN at diagrams and explanations. If you would explain side imaging, I believe it would help others wrap their head around 360 technology, since it is based on SS.
The Lucky Duck is offline   Reply With Quote
Old 05-14-2015, 08:20 PM   #29
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by Beach Caster View Post
Thanks TL. So what are the horizontal lines that appear at the top of my dragon fly screen pics? Propwash? Our fishing lines were on the bottom.
Surface clutter, stuff floating on the top part of the water.

Quote:
Originally Posted by Beach Caster View Post
That appears to be a big fish that appears just two feet under the surface in my second pic?
It is, AND since that part of your cone is maybe 2-4 feet in diameter you know right where it was.

Quote:
Originally Posted by Beach Caster View Post
One other question regarding the side profile of the bottom, is the image probing 6-8 feet into the bottom of the river and showing us whether its sand or rock? If so how can you tell which is which?
Great questions:
The sonar waves penetrate into softer bottoms but not in feet, more like inches and it doesn't penetrate into hard surfaces very well at all. The harder the bottom is the more vibrant your return is and this causes the image displayed to be brighter white. Bright white being rock, fading to a muted grey for mushy bottom.

Quote:
Originally Posted by Beach Caster View Post
Sometimes there are what appear to be logs under the sand 3-4 feet, can the down imaging actually tell me what's under the bottom 3-4 feet?
BC
Referring to the image at the top of this thread where I show how a sonar cone measures distance to transducer for an entire cone shape then converts that into a line.That line is displayed as the A scope.

Now look at the image below of the shape of down imaging, where the sonar is a very narrow beam.

it's returning much crisper images because it covers a far narrower area.

So, yes you are seeing a log that is 3 or 4 feet below the first return for bottom but that log isn't buried in the bottom. It's on a slope Where the down imaging is seeing it at 25 feet(in this picture) but is also seeing the bottom at 15 feet and displays that as well.

If the bottom is soft and light grey colored, any object on the slope like a log or rock will return a much whiter colored return and be visible in the vertical grey area of the softer bottom. Making it appear to be buried but actually just on a slope.



Here is an outstanding down image picture to define exactly what we are talking about. You can see trees on the top of the hump but also the trees on the side of the slope are showing up as well. The narrower beam of down imaging is able to discern between this small differences where as standard sonar has so many more returns in the round cone shape that it mostly will blank out any thing that is below the first bottom return.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-14-2015, 08:31 PM   #30
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by P Stewart View Post
Do you have any tips for determining bottom composition?
On side imaging and down imaging bottom composition is whiter the harder it is. Rock being bright white to mud being a soft grey color.

On normal sonar it's the same, it just depends on your color palette. Mine is blue fading to red then to yellow for the hardest bottom.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-14-2015, 09:09 PM   #31
ccw
King Salmon
 
ccw's Avatar
 
Join Date: Feb 2010
Posts: 8,714
Default Re: Fish Finder Basics

Quote:
Originally Posted by Smj View Post
CCW...

..It really helps to know what conditions are. ....

Question? Do YOU know what you're seeing on the screen? LOL I like the pictures your unit puts up, they're close to mine, and mine is ancient! My buddies ultra fancy $$$ unit doesn't have nearly the picture, or at least I've had trouble getting it.
Smj
Smj and The Likes: Thanks for your thoughtful feedback.The more different conditions I use it under and the more days I use it under known conditions, the better I learn and appreciate its detail and what adjustments do in various environments.

My unit is a new HDS7 (button version) floor model I got from Bob's this spring. I turned it on springer fishing, but just to confirm what was under the anchored boat, not to locate the fishing spot. It really lit up some days.

  • That first pic was at the upstream mouth of Carrol's channel. I took the boat "salmon scouting" the first day after the season closed (last Sunday) just to patrol water during good fish passage where I suspected fish lay. There was a little flotsam in the water column, but there is no fishing gear in the water and I was "hovering" over slowly moving water. I'm fairly confident some were fish.
  • The rest of the pics were all taken while anchored in a shallow water spot the day prior. My fishing gear was lightweight and cast back behind the boat so wasn't likely in the cone. The water was moving slowly. There was no flotsam, the water shallow and clear. There are no logs there.




CW
__________________
"To strive, to seek, to find and not to yield."

(from Ulysses - Tennyson, 1833)
ccw is offline   Reply With Quote
Old 05-14-2015, 11:47 PM   #32
The Lucky Duck
Tuna!
 
The Lucky Duck's Avatar
 
Join Date: Jun 2007
Location: Eugene
Posts: 1,877
Default Re: Fish Finder Basics

Good stuff here. I find the down imaging not useful for finding fish, but somewhat useful for structure. Here's why. If a fish appears 70 ft down on the DI screen the fish maybe under the boat and just outside the cone or a very shallow fish to the right or left of the boat. It just means it is 70 ft from the transducer. The side imaging works better if you are moving, because anything that penetrates the "plane of the goal line" is marked and this can be a significant swath of water. At Odell it is generally 100 feet deep. I can see schools 100 feet on either side of the boat at speeds up to 15 mph
To understand the 360 you must understand the side imaging concept, then spin it like radar. Now (in 100 ft of water) you are looking at a circle of 200 ft diameter. That's a ton of area, the fish will be small rice pellets.
The bottom appears as the white circle around the perimeter. Even in shallow water it see 120 feet or more, but if the bottom is 30 feet away your (clear water) circle is only a 30 ft radius. You might get lucky and see fish against the white bottom return but not likely, white on white.

Here is a screenshot of a school of kokanee at Cresent. It is a large school, they are at 2:00 from 50-85 feet away. (Using the 30 ft rings for reference). I don't know how deep this school is. I only know that they are less than 85 feet deep. As I get closer eventually I will start marking them in the cone of standard sonar, then I will know and drop on them.

This is the same school of fish, just a few seconds later. a few things to note.
1. I am not getting much closer, (and I am trying)
2. The return is very whispy, (I know this means that they are running straight away from me. How do I know that?
When the fish swim away from the transducer the return is pinging off their tails rather than their back or side. (Whispy return)
This school was very shallow (10-20 ft) and I was not able to get on top of them. It was a bright day with no wind and they were afraid of the boat. We finally started casting at them. We only got 1, probably because I had them stressed by chasing.

Can you spot 3 schools in this shot?
First the school at 4:00 and 10:00 are the same school, this is a weird thing that Humminbird does I am not sure why, so you will just have to trust me.
There is however a school at 8:30. It appears to be on the bottom. But remember you only know how far they are away from transducer. These fish are likely 50 ft or so. Also worth noting the bigger school are tightly bunched. This usually means they are stressed, (probably a Mackinaw in the area) The school at 8:30 is the one I am interested in.
Also the streaks near the middle is prop wash from my boat trying to maneuver on the fish. Also note 2 prop wash returns, one from my main, and one from the Minnkota on the bow, tracking right.

This screenshot was certainly combined with a lot of screaming from a very exited skipper proclaiming the "mother load". We have hundreds of fish (kokes) within 35 ft of the boat, some are 12ft below. Notice the "circle" of fish, (rice pellets), this means I am RIGHT on top of them. We likely thinned these guys out a bit.
The Lucky Duck is offline   Reply With Quote
Old 05-15-2015, 01:15 AM   #33
Hubbs
Tuna!
 
Hubbs's Avatar
 
Join Date: Dec 2013
Location: Sherwood, OR
Posts: 1,098
Default Re: Fish Finder Basics

It seems that the standard sonar is pretty limited when fishing in rivers where the depth is generally less than 40' or so. The cone angle is fairly narrow, and generally gets more narrow as the frequency gets higher. For example, with a 200kHz cone on my HDS, I am only seeing about 8' of the bottom when looking in 40FOW. Am I correct on that?

It would seem the side image/down image would be better when scouting for fish. With the side scan I can see 80+ feet to either side of the boat, and with down imaging I can see what's under the boat. Putting the side image on the left half of the screen and the down image on the right half of the screen, I should be seeing a three dimensional representation of what's down there, correct? And using a blue color palate, the fish are going to show as white marks, with larger fish showing as larger white marks. Am I correct on that part too?
Hubbs is offline   Reply With Quote
Old 05-15-2015, 03:33 AM   #34
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by Hubbs View Post
It seems that the standard sonar is pretty limited when fishing in rivers where the depth is generally less than 40' or so.
Standard sonar has limitations, but it's important to remember that ALL forms of sonar we are talking about, standard, down imaging, side imaging, and 360, all have their limitations. What you want to do is use them in conjunction to form a much much better picture of what is really down there.

Quote:
Originally Posted by Hubbs View Post
The cone angle is fairly narrow, and generally gets more narrow as the frequency gets higher. For example, with a 200kHz cone on my HDS, I am only seeing about 8' of the bottom when looking in 40FOW. Am I correct on that?
Close that's the radius, you need the diameter to know the entire size of the cone. Here is a chart.
200khz = 20 degree angle
83khz = 60 degree angle



If you read some of the thread above you will see where a comment was made on someones picture that they were only running 200khz. The reason for that comment was for the narrow cone angle and limited view.

Also keep in mind the 83 khz is a 60 degree angle so that cone is fairly substantial at 40 fow, 46 feet in diameter

Quote:
Originally Posted by Hubbs View Post
It would seem the side image/down image would be better when scouting for fish. With the side scan I can see 80+ feet to either side of the boat, and with down imaging I can see what's under the boat. Putting the side image on the left half of the screen and the down image on the right half of the screen, I should be seeing a three dimensional representation of what's down there, correct?
Here are the general shapes of side scan and down imaging sonar.

There are 2 large glaring deficiencies. 1) If a fish swims from left to right in front of or behind your down or side imaging.. you will never see him. However, he would pass through your standard sonar cone. 2) If a fish passes quickly through the wall of the down or side imaging he appears to be a minor blip on the screen because of how thin the cones are. If you have your standard sonar to back it up you will see the fish arch and the correlating mark on the down imaging.

Remember down imaging and side imaging are not there to replace standard sonar. They are there to enhance it. None of the three could ever do any of the others job completely.

Quote:
Originally Posted by Hubbs View Post
And using a blue color palate, the fish are going to show as white marks, with larger fish showing as larger white marks. Am I correct on that part too?
When I switch color palettes, for side or down imaging, on my unit the fish marks change to blue also as well as all the other returns. It's just brighter(almost white) returns for hard things like rocks, and darker blue for softer things.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-15-2015, 09:31 PM   #35
ccw
King Salmon
 
ccw's Avatar
 
Join Date: Feb 2010
Posts: 8,714
Default Re: Fish Finder Basics

So what's the cone angle when my transducer is set to 50 kHz ?

CW
__________________
"To strive, to seek, to find and not to yield."

(from Ulysses - Tennyson, 1833)
ccw is offline   Reply With Quote
Old 05-15-2015, 11:29 PM   #36
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by ccw View Post
So what's the cone angle when my transducer is set to 50 kHz ?

CW
First off let me say we are no longer in Fish Finder Basics now. This is a more advanced discussion

That being said... it depends. I know, I know... worst answer EVER!

It depends on who the manufacture is and what kind of transducer you have. 50khz is a more specialized frequency. The lower the frequency the better penetration the signal has. So 50 khz is used for deep water, by deep water I mean 150+ feet deep. If you are going to use it 500 feet deep you don't want a 60 degree cone and have a target area of a 700 foot in diameter cone. What the user then has to decide is "How deep will I be needing the transducer to go?" or "How many transducers do I want/need?". For coastal there is a50 khz 45 degree angle but you can get a 50khz 19 degree and probably other variations depending on who makes the transducer.

A quick search of Airmarr shows they make
50 khz 45 degree/200 khz 12 degree
and
50khz 19 degree /200 khz 6 degree.

These transducers are designed to look deep so the angles need to be cut down and the wattage needs to be pumped up, the deeper you want to look the more you are going to cut down the angle so that you are not getting massive returns all jumbled together.
__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Old 05-16-2015, 11:14 AM   #37
Northwestnative
Steelhead
 
Northwestnative's Avatar
 
Join Date: Feb 2012
Location: vancouver
Posts: 387
Default Re: Fish Finder Basics

Didn't mark many this morning at Davis but drove over this. Shad maybe? Not sure why it's sideways.
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	2089
Size:	40.8 KB
ID:	333354  
__________________
18' north river scout
Northwestnative is offline   Reply With Quote
Old 05-16-2015, 07:48 PM   #38
The Likes
Tuna!
 
The Likes's Avatar
 
Join Date: Jul 2012
Location: Salmon Creek Wa
Posts: 1,375
Default Re: Fish Finder Basics

Quote:
Originally Posted by Northwestnative View Post
Didn't mark many this morning at Davis but drove over this. Shad maybe? Not sure why it's sideways.
There are several larger fish in that image. Smaller fishing being blue outer red center on that color palette, the medium with blue outer red with some yellow on the core, and larger fishing being blue with yellow core. I see 3 bigger fish, a couple medium size fish, and lots of smaller fish on your history. With 2 small-medium size fish under your boat.
I notice you are running 200khz which is a 14' diameter cone at 40 fow. I'm curious if you have a specific reason for running the narrower cone? For me the size of the cone at the bottom is ok but it's such a narrow cone all the way up that in 20' you are only seeing about a 8 foot circle. At 10' the cone is 3.5 feet wide. So a fish could swim directly under your boat at 10-15 fow and you might not see it on your FF.

__________________
“Tell me and I forget, teach me and I may remember, involve me and I learn.”
~ Benjamin Franklin
The Likes is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Cast to



All times are GMT -8. The time now is 02:37 AM.

Terms of Service
 
Page generated in 0.45594 seconds with 53 queries