View Full Version : INFO: [Graphs/Depthfinders] Calculating cone diameters

BleuGhill

01-07-2008, 09:18 PM

I have a simple Excel spreadsheet that will calculate the cone diameter for your graph/depth finder for a given cone angle and depth. For anyone needing this, send me a PM. Forumula included if you want to roll your own.

Formula: 2*d*TAN((Pi/180)*(ConeAngle/2)) where d=depth and Pi =3.14

Quick Calcs for cone diameter:

======================================

12° Cone Angle > 1/5th of depth (Depth/5 )

For example, at 100' depth, you would 'see' approximately 20' of bottom surface area

20° Cone Angle > 1/3rd of depth (Depth/3)

35° Cone Angle > Depth x .6

======================================

Hope this helps someone. If anyone finds a mistake, please let me know.

BleuGhill

Cane Pole

01-07-2008, 09:54 PM

Go to a tangent table. Select the your cone (tangent) angle and get the tangent of the cone angle. Multiply this number (tangent) by the depth. This calculation will render viewable area diameter.

That was easy.

Yep. I know. It is an isosceles triangle. But it's pretty close to the right answer.

tangent table link. Check it out.

http://www.science-projects.com/TangentTable.htm

CrappieHound

01-07-2008, 10:08 PM

Canepole,

How would you calculate the viewable area diameter of a 20/50 transducer? Im pretty sure that's what I have.

BleuGhill

01-07-2008, 10:12 PM

:)

..but I think I'll just write the 'quick calcs' on a piece of duct tape and stick it on my graph ha ha. I'm afraid a big ol' table won't fit in my boat!

BleuGhill

PanMan_VA

01-07-2008, 10:14 PM

Canepole,

How would you calculate the viewable area diameter of a 20/50 transducer? Im pretty sure that's what I have.

depth*tan(10°)=viewable area radius for 20° transducer

depth*tan(25°)=viewable area radius for 50° transducer

multiply radius by 2 to get the diameter

Darryl Morris

01-07-2008, 10:20 PM

Do you gents do that math in your head? I do alot of things in my head too but I'm sure you wouldn't believe what all it is, LOL. I'm convinced my high school math teacher didn't know crap about fishing, lol.

Jerry Blake

01-07-2008, 10:21 PM

What you really want to know is how close you (or your boat) are to objects on your screen, right? Easiest way to find that out is to put a half-ounce or large weight on your line and mark your line at 10, 15 or 20-feet with a permanent marker. Then lower the weight to a known depth and slowly (slow enough that your line remains vertical) move your line towards your transducer while watching your screen. When your weight begins showing up on your graph the distance your line is from your transducer is the distance (horizontally) all objects at that depth are when they first come on your screen from the same direction. If your transducer is not pointing straight down then that distance will vary depending on which side of the transducer an object is on.

Keep in mind that increasing your sensitivity can effectively increase your cone angle because objects that are on the periphery of your graph's view may show up at higher sensitivity settings and not show up at lower settings.

BleuGhill

01-07-2008, 10:39 PM

:)

Haha...hold on folks!

Didn't mean to turn fishin' into high-tech ciphering, and now I hate myself for posting this! Can I holler 'slips'?

I always went around in a cross-eyed daze wondering just how much the transducer was actually 'seeing' under my boat - and figured some new folks might find some use in a quick way to get a close estimate. So I offered up two ways:

1. Quick calculation that they could write on their hat or on a piece of tape - based on the depth. I didn't include every cone angle obviously.

2. For folks with Excel on their 'puter, they could basically copy/paste the formula and get it chugging.

Good tip Jerry! I'm gonna try it!

(...backin' outta here....slowly...) :)

BleuGhill

Cane Pole

01-07-2008, 10:47 PM

Canepole,

How would you calculate the viewable area diameter of a 20/50 transducer? Im pretty sure that's what I have.

Pan Man formula are correct. I just too lazy to multiply by 2...:D Look up the tangent in the tangent table or use your engineering calculator.

CrappieHound

01-08-2008, 08:13 AM

Thanks PanMan, CanePole. That is very interesting. I'm actually seeing more of the bottom than I previously thought. Now I will have to tackle the JerryB problem.

Good things to ponder in the off season.

CH

Cracker68

01-08-2008, 12:27 PM

Thanks PanMan, CanePole. That is very interesting. I'm actually seeing more of the bottom than I previously thought. Now I will have to tackle the JerryB problem.

Good things to ponder in the off season.

CH

Offseason??? Man the fish are biting now, Some of the best fishing is in the winter. Wind let up I'm out there.

Ga_redland

01-08-2008, 07:59 PM

Cracker68 You beat me to it

Darryl Morris

01-08-2008, 08:14 PM

It doesn't happen all the time but it's happened to me a few times to see a fish on your graph, slowly pull your boat around so you can get your jig in that exact spot, adjust the depth of your jig to the depth of the fish, then THUMP - FISH ON. Jerry has told me stories of seeing his jig on the graph and watching a fish come after the jig. Thump, fish on!

CanePole,

So according to your chart a 60 deg cone angle @ 10ft would =

10x1.7317=17.317 ft viewable diameter ??? (Math isnt my specialty)

Thanks for the info fellas

BleuGhill

01-09-2008, 05:05 PM

CanePole,

So according to your chart a 60 deg cone angle @ 10ft would =

10x1.7317=17.317 ft viewable diameter ??? (Math isnt my specialty)

Thanks for the info fellas

Although you were asking CP the question, I thought I'd supply with a full chart for your 60° cone angle:

60° Cone Angle

Depth - Cone Diameter

4 - 5

6 - 7

8 - 9

10 - 12

12 - 14

14 - 16

16 - 18

18 - 21

20 - 23

22 - 25

24 - 28

26 - 30

28 - 32

30 - 35

35 - 40

40 - 46

45 - 52

50 - 58

100 - 115 **

** As you can see, for an depth, just multiply it times 1.15. Not too convenient out on the boat, so you can either print this chart or rough guess it based on the chart. In your case, basically just remember that your viewable area is a little more than the depth!

Hope this helps.

BleuGhill

Cane Pole

01-09-2008, 05:41 PM

CanePole,

So according to your chart a 60 deg cone angle @ 10ft would =

10x1.7317=17.317 ft viewable diameter ??? (Math isnt my specialty)

Thanks for the info fellas

Cone angles are relative to the sensitivity setting. It is all Voodoo.

I just gave a quick guesstimate method of relative cone angle view. As I said, Pan Man is right. To use trig properly you have to use right angles. To generate a right angle, you divide the cone angle by 2. After the cone angle is divided by 2, look up the tangent of this number (1/2 of the cone angle). Multiply this by the depth. This gives the radius. Now multiply this by 2. This equals the diameter.

Cone angle = 60

Divide this by 2 = 30

Tangent 30 degrees = .57735

Depth of 10 ft times the tangent .57735 = radius = 5.7735

5.7735 times 2 = diameter = 11.147 viewable.

This is only if you have the sensitivity set so that it represents a true 60 degree cone. Ha.

If you run a little high sensitivity (as I do) then my first method is just as good as any.

Magic stuff here.

Tom

Thanks Bleughill that is much easier .....LOL

Cane Pole

01-09-2008, 05:51 PM

Thanks Bleughill that is much easier .....LOL

Don't forget, these numbers are relative to the sensitivity(gain) setting. Change the sensitivity, throw the book away...

BleuGhill

01-09-2008, 06:41 PM

You're welcome BYG! Glad to help. After doing the calculations, I just wanna know the bottom line, i.e. just a simple way to estimate the viewable area at any depth. Then I toss the dang computer and forumulas. I'm afraid that geek stuff will cloud my fishing concentration! :eek: :)

Cane Pole

01-09-2008, 06:56 PM

You're welcome BYG! Glad to help. After doing the calculations, I just wanna know the bottom line, i.e. just a simple way to estimate the viewable area at any depth. Then I toss the dang computer and forumulas. I'm afraid that geek stuff will cloud my fishing concentration! :eek: :)

I take mt laptop fishing with me. I like company.;)

gabowman

01-09-2008, 07:08 PM

It doesn't happen all the time but it's happened to me a few times to see a fish on your graph, slowly pull your boat around so you can get your jig in that exact spot, adjust the depth of your jig to the depth of the fish, then THUMP - FISH ON. Jerry has told me stories of seeing his jig on the graph and watching a fish come after the jig. Thump, fish on!

Now tell me....which side of the cone does the fish swim into first so you can move over there?!?:confused: :D

Cane Pole

01-09-2008, 07:22 PM

Mine always show up on the right hand side of the sonar first. So they gotta be coming in from the right. Fish right!:D

Darryl Morris

01-09-2008, 07:25 PM

Now tell me....which side of the cone does the fish swim into first so you can move over there?!?:confused: :D

It's not about swimming into or out of the cone. As I move around the crappie condo I'm watching my sonar, usually in 21-30' (only a 7-10' view of the bottom, 3.5-5' view at mid-depth) of water this time of year. I can tell the difference in the sonar return of the cover and a fish. My transducer shoots through the hull a few feet back from the bow of my boat. So what I'm looking at on the right side of the graph is essentually right under me and I'm fishing out in front of me. When I see a nice fish sitting there under a branch of bamboo I use the trolling motor to move back and put the jig or minnow right where I was sitting. It's easy to find the cover but the crappie aren't always stacked up all over it. Sometimes they are only on one side or something like that. We call it the dinning room. When you see fish, fish there, not away from it and hope they come to you. Use the sonar to locate cover, yes, but also use it to precisely locate the fish.

Darryl Morris

01-09-2008, 07:41 PM

As far as telling which side of the cone a fish swims in at is impossible to determine by looking at your sonar screen. That's conditional upon which direction your boat is moving and what direction the fish is swimming. Too many possibilities. Your boat can be moving in 360 variant directions and the fish can swim into the cone in 360 different locations. Impossible to tell which side of the cone the fish entered. Besides that, your sonar unit is graphically showing you everything in the cone in split second vertical snapshots as it scrolls to the left of your screen. It is however possible to determine where the fish is when just laying there in the brushpile. You know where you are at relative to your transducer when the transducer pinged the fish. Move around to put your bait there. If it's just laying there and you are moving forward, the fish entered the front of the cone and if you back up you can put your jig right there. The same applies to the other directions, moving left, go right; moving right, go left; moving backward, go forward. You see it laying there, get'em!

BleuGhill

01-09-2008, 07:58 PM

Very, very good Darryl - and in terms I can understand. Thanks!

-BleuGhill-

wannabe fisherman

01-10-2008, 07:39 AM

I take mt laptop fishing with me. I like company.;)

I think Cane Pole takes his whole computer room with him, it's mounted right in front of his boat. I seen the pics!!!:D :D

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