mathematic sonar question

[MGB]

I have forgotten how to figure the diamiter of the cone from the transducer.

If your transducer is a 20* and you are in 30' of water your cone is 10' diameter at the bottom. I do remember 20* cone was 1/3 (+/- a couple inches) the depth. What is the formula to figure this out on a 20*, 35*, 12*?
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[Theekillerbee]

That kind of thinking hurts my brain Mike!
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[Tarponjim]

Sonar waves do not shoot down in an exact cone, and depend on sensitivity setting. Here's a link that may help and has a table for narrow cones. [url "http://www.vexilar.com/help/tips/tip006.html"]http://www.vexilar.com/help/tips/tip006.html[/url]
Lowrance also has good info on its website.
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[Fishhound]

Hey MGB,

I made a couple of posts on the floattube board about this. Here is a link to one of them:

[url "http://www.bigfishtackle.com/cgi-bin/gforum/gforum.cgi?post=226773;sb=post_latest_reply;so=ASC;forum_view=forum_view_collapsed;;page=unread#unread"]http://www.bigfishtackle.com/...;;page=unread#unread[/url][font "Times New Roman"][size 2] [/size][/font]
[font "Times New Roman"][size 2][/size][/font]
Anyway, you can use these for (S.W.A.G.(s)) "guesstimates" of the cone angles:

10 degrees = 0.23 times the depth
20 degrees = 0.35 times the depth
30 degrees = 0.53 times the depth
40 degrees = 0.72 times the depth
50 degrees = 0.93 times the depth
60 degrees = 1.15 times the depth
70 degrees = 1.4 times the depth
80 degrees = 1.68 times the depth
90 degrees = 2 times the depth
100 degrees = 2.38 times the depth
110 degrees = 2.85 times the depth

[font "Times New Roman"][size 2]Sorry, about the link there. You may have to cut and paste it in your browser to go to the post. I had a problem with putting it on here and getting it to work. If anyone knows a better way to post a link, I would appreciate the help. Thanx.

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[BearLakeMack]

[font "Comic Sans MS"][black][size 3]Hey, Mike![/size][/black][/font]
[font "Comic Sans MS"][black][size 3][/size][/black][/font]
[font "Comic Sans MS"][black][size 3]Though your sonar may not be a "true" cone you can calculate the theoretical diameter of the cone at any depth based on the cone angle. It's a matter of simple right angle trigonometry. Here is a link to a right angle trig calculator which is simple to use.[/size][/black][/font]

[black][size 4][url "http://www.pagetutor.com/trigcalc/trig.html"]Right angle trig calculator[/url][/size][/black]

[font "Comic Sans MS"][black][size 3]When you go to this calculator supply, the following data:[/size][/black][/font]
[font "Comic Sans MS"][black][size 3][/size][/black][/font]
[font "Comic Sans MS"][black][size 3][#ff0000]X[/#ff0000] = 1/2 your cone angle (ex.=20 cone, enter 10 in "[#ff0000]X[/#ff0000]" value)[/size][/black][/font]
[font "Comic Sans MS"][black][size 3][/size][/black][/font]
[font "Comic Sans MS"][black][size 3][#ff0000]B[/#ff0000] = your depth (ex.=enter 20 for 20 ft deep in "[#ff0000]B[/#ff0000]" value)[/size][/black][/font]
[font "Comic Sans MS"][black][size 3][/size][/black][/font]
[font "Comic Sans MS"][black][size 3]Hit the calculate button which will automatically fill in all the values.[/size][/black][/font]
[font "Comic Sans MS"][black][size 3][/size][/black][/font]
[font "Comic Sans MS"][black][size 3][#ff0000]A[/#ff0000] = will be the radius of the cone diameter. Times the [#ff0000]A[/#ff0000] value by 2 and that will be your cone diameter.[/size][/black][/font]
[font "Comic Sans MS"][size 3][/size][/font]
[font "Comic Sans MS"][size 3]This is very simple. Try it![/size][/font]
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[MGB]

Thanks everyone for the valuable information. That Right Angle Trig Calculator is a good tool.
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[RipNLips]

Here's the equation for the method BLM described:

diameter=2*(depth*TAN(angle/2))
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