Cone angle geometry

[NoSchoolin']

I was hoping someone with a greater understanding of geometry than myself could work out a few numbers. I would like to know what the actual width is that the standard 20 degree cone angle can see at various depths. I would like to know starting at 10 feet and go in increments of 10 feet down to a max depth of 50. Basically, I need this information to settle an argument with a guy I fish with and unfortunately am mathmatically challenged.
If someone could work these numbers for me, I would be greatly appreciative.

[Bulletny]

This is a general rule of thumb for a 20 degree cone angle but should put you with-in inches of actual coverage.
20 degree cone angle = 1/3 of depth.
10' = 3.3'
20' = 6.7'
30' = 10'
40' = 13.3'
50' = 16.8'
Hope this helps.. Bulletny

[war-n-peace]

Using the law of SINES: the sine of 10 degrees is 0.173648177666930348851716626769315 then multiply by 2 for your 20 degree cone =0.34729635533386069770343325353863 then multiply that by each foot of depth you want to find ie:10x0.34729635533386069770343325353863=3.4729635 533386069770343325353863 or just under 3 1/2 feet in diameter at 10 feet deep, Multiply that by 2 for 20 feet, by 3 for 30 feet etc.

Bill W.

[Al]

Go get an office supply store or Wal-Mart, K-Mart, school supplies. Get block graft paper and an varible two sided angle marker used in geometry. Graft out the angle you want after establishing the top of the water, perpendicular line and how many feet deep, say one foot for each block. Mark how deep you want bottom. Split your angle one each side of perpendicular and you have it.

[ETT]

No matter what depth the diameter of the 20 degree cone will be very close to 1/3rd the depth.

[pepe]

i have a bottom line depth finder. i called the factory and asked, what the cone angle was on my depth finder. they told me it was the opposet of what we think. the shallower the water, the more of the bottom we see, the deeper the water,(say 100ft.) the less of the bottom we see due to the fact that the power was more consentrated to get to the bottom. we really dont see much of the bottom as we think. how many times have you been out fishing and not seen a fish on your locater and still catch fish. in other words they told me, it was a variable view. you cant just take a 20 degree cone angle and project it out to see how much of the bottom you can see. if you could do that, imagine how much of the bottom you could see if you were in 200ft. of water. i hope that i explaned it right. if not i hope someone will tell me. good luck....pepe

[SUPERTROLLER]

pepe, you are incorrect. The above answers are right. I think you may be referring to their side-finder technology in your response. You wouldn't make much bottom contact when in deeper water but in shallow would make a lot of contact. The power would affect how far away you were marking fish to the side. I think you are just talking two different situations.
(Hey, If I'm wrong-- someone tell me! I'm okay with it.lol.)

[war-n-peace]

All you ever wanted to know about sonar but were afraid to ask.

http://www.fieldandstream.com/tactics/fs/sonar.html

Bill W.

[pepe]

sorry, i guess i"ll have to do some more investigating on my depth finder and find out for sure. thanks for telling me, or i might have gone on thinking the wrong way. pepe

[pepe]

i decided to get my owners manual out and see what it had to say about the cone angle of my transducer. here it is, 200khz for the bottom transducer and it goes from a 18 degree in shallow water(it doesn"t say what shallow is) and goes to 9 degree thereafter. thats on the bottomline tournament master with the sidefinder. the sidefinder cone angles are 9 degrees all the time with a 455khz. power output. thats probably where i got the idea of not seeing as much of the deep bottom as the shallow end.sorry again if i mislead anyone..pepe