Understanding Range ?

[Hickory Legend]

So let say you are shotting out 100ft left and right and the boat is setting in 6 inches of water. If there is a rock at the edge of the graph one would believe it to be 100 ft or so from the boat. Right!!

Now lets say you are still on 100 ft range and setting in 50 ft of water. If the rock is still on the edge of the graph is it 100 ft from the boat or 50 Ft from the boat?

Now say you are in 90 ft of water, Black almost to the edge of the graph and there is a rock on the edge of the graph is it 10 ft from the boat or 100 ft from the boat while still on 100 ft range ?

Not sure why this poped into my head but someone set me streight....

721 ProXP

[Bryanmc57]

I've wondered the same thing... Hope one of the experts answers this.

[Lassiter]

I believe it is still 100' from he boat. I don't think depth has any bearing on side scan. At least thems my thoughts. I'm sure Doug or Mike will set us straight soon

[db_db]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Lassiter &raquo;</td></tr><tr><td class="quote">I believe it is still 100' from he boat. I don't think depth has any bearing on side scan.</td></tr></table>

Not Doug or Mike...but I'd agree with you. I believe that it will be 100' away still. Just that at a deeper depth everything that you see from the water column out to the edge should be crammed in a tighter picture (with all objects being smaller). That's my thoughts on it.

[Bryanmc57]

If that's the case, in 50ft of water on a 100' range something would have to be pretty big to show up I would think. On an 898 with 100 ft represented by 2 inches of screen, an object would have to be roughly 12ft to be 1/4 inch on the screen...

[stillbear]

Pro xp if the rock or boulder shows up on the outside edge of the screen
it will be that distance from the boat regardless of the depth.If you are scanning
100 ft. it will be 100 ft from the boat regardles of depth. Example set your machine
to scan 100 ft wide find a object 70-100 ft away.Switch scan width to 50 ft object
will disapear.The closer the scan width the bigger the object will appear on your
screen.I like to scan 50 wide on my 997 looking for brush piles or specific detail. Hope this helps. Gary

[Hickory Legend]

Lets look at this, if you are on a 100 ft scale, in 75 foot of water(being 75% of the screen is black) an object 100 ft away would show up at the edge ( what ever size it is, being big enough to see, not the point though) another object under the boat actually would be at the 3/4 or 75% across the screen where the bottom starts showing up.

Case 1
If this is the case then the object under the boat would show up 75 ft from the boat out on the screen.

Case 2
same deal as above but if an object is 100 ft from the boat and shows up on the edge, and an object under the boat show at the bottom, 3/4 across the screen then the 100 ft between the 2 object wouldn't be to scale in the 25% of the screen that shows bottom.

Case 3
Same as above. an object below the boat is shown 3/4 out on the screen on the bottom, then an object 25 ft from there would be on the edge of the screen. 100 Ft from the boat from object to transducer, yet only 25 ft from the side of the boat.

Case 4
Your in 100 ft of water 100 ft away from the bank. The bank slops at a 45 deg angle down under the boat there's BIG BOULDERS laying all over the bottom. I would think that they wouldn't show up being that the screen is black all the way to the bottom.

Not that you would run a unit like this just trying to figure out where objects are.

Does anyone else see my confusion!!!

721 Pro XP


Modified by 721 Pro XP at 7:56 AM 12/29/2010

[Hickory Legend]

Here is an image.


If X marks 100 ft out from the boat.

if Y marks the bottom which is around 50 ft Then does Z mark 75 ft out from the boat?

If anything on the edge is 100 Ft away then the scale has to screwed close to the bottom edge.

Anything out 10 to 20 ft from the boat, left or right is going to show a minimum of 50+ ft from the boat. So the scale is going to be off the way I see it.


721 Pro XP


Modified by 721 Pro XP at 8:41 AM 12/29/2010

[Wayne P.]

Do you use Humviewer?
If you do, stop a recording in the SI view and put the pointer on the center line and then move it to the sides while watching the readouts at the bottom. You will see how the distances are represented.

[db_db]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by 721 Pro XP &raquo;</td></tr><tr><td class="quote">Lets look at this, if you are on a 100 ft scale, in 75 foot of water(being 75% of the screen is black) an object 100 ft away would show up at the edge ( what ever size it is, being big enough to see, not the point though) another object under the boat actually would be at the 3/4 or 75% across the screen where the bottom starts showing up.

Case 1
If this is the case then the object under the boat would show up 75 ft from the boat out on the screen.

Case 2
same deal as above but if an object is 100 ft from the boat and shows up on the edge, and an object under the boat show at the bottom, 3/4 across the screen then the 100 ft between the 2 object wouldn't be to scale in the 25% of the screen that shows bottom.

Case 3
Same as above. an object below the boat is shown 3/4 out on the screen on the bottom, then an object 25 ft from there would be on the edge of the screen. 100 Ft from the boat from object to transducer, yet only 25 ft from the side of the boat.

Case 4
Your in 100 ft of water 100 ft away from the bank. The bank slops at a 45 deg angle down under the boat there's BIG BOULDERS laying all over the bottom. I would think that they wouldn't show up being that the screen is black all the way to the bottom.

Not that you would run a unit like this just trying to figure out where objects are.

Does anyone else see my confusion!!!

721 Pro XP&lt;br /&gt;&lt;br /&gt;
Modified by 721 Pro XP at 7:56 AM 12/29/2010</td></tr></table>

If you are in 100ft of water as in your last scenario and you are scanning 100ft out and at that distance it is 100ft deep also, then the screen should be completely black(water column).

Just because an object is 3/4 of the way out (on the screen) doesn't represent 75ft when scanning 100ft. You have to recognize that the 0-100ft scan distance starts where the water column ends and goes out to the edge.

In other words...divide only the part showing the bottom into 4 equal parts and that should represent the 25-50-75-100ft points.

[Hickory Legend]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by Wayne P. &raquo;</td></tr><tr><td class="quote">Do you use Humviewer?
If you do, stop a recording in the SI view and put the pointer on the center line and then move it to the sides while watching the readouts at the bottom. You will see how the distances are represented.</td></tr></table>

No I have apple computers. I have boycotted Bill Gates ever since he wouldn't loan me money for a new boat. LOL

721 ProXP

[Hickory Legend]

<table width="90%" cellspacing=0 cellpadding=0 align=center><tr><td>Quote, originally posted by db_db &raquo;</td></tr><tr><td class="quote">

If you are in 100ft of water as in your last scenario and you are scanning 100ft out and at that distance it is 100ft deep also, then the screen should be completely black(water column).

Just because an object is 3/4 of the way out (on the screen) doesn't represent 75ft when scanning 100ft. You have to recognize that the 0-100ft scan distance starts where the water column ends and goes out to the edge.

In other words...divide only the part showing the bottom into 4 equal parts and that should represent the 25-50-75-100ft points.</td></tr></table>

I agree with You on this.

Your scale only goes from the bottom of the water column to the edge. So the bigger the water column the smaller the scale and detail you will get. So you should always have a small water column to keep your detail from being compressed.

So in the picture above 100 ft of bottom is compressed into 1/4 of the screen.

It kinda had me thinging hard on this earlier,
Thanks for the help

721 Pro XP


Modified by 721 Pro XP at 5:37 PM 12/29/2010

[justbass]

if you go to youtube and search humminbird you will have several videos and there is one the explains all the distance and what not.i also find plenty of helpful info on hb's facebook page.

[T Mike]

721, Great question.. Here are some images I got to help explain.

In simple terms, Si operates the exact same as sonar in terms of determining distance. If you draw a straight line from the ducer to the object that determines the distance.



If you really want to get technical here is some detail info.



Think of it this way and I believe this has already been stated. If you are in 100ft of water and your beams are out 100ft your entire screen will be dark blue showing no lake bottom (or very very little lake bottom) indicating depth of water. So if a object is at the very edge of your screen it is 100ft away but could be right under the boat vs 100ft off to the side. Confusing but that is how it works.

If you section out a screen with lines this is how distance/depth is determined from the CENTER LINE. Having said that the screen is suppressed some ie putting 100ft of data on a small 1197SI screen. In the grand scheme of things I have found the GPS to be pretty dang gone accurate using the cursor to mark waypoints off to the side but having said that you do need to realize that the cone of a sonar isn't exactly pin point either when you go to refind that waypoint because Sonar beam at 30ft of water is 30ft (in dual beam). So you can still be off 27ft and still see the object you just waypointed.. GPS is almost pinpoint on land/surface of water but when you add depth is when it gets muddled some. Thankfully the shallower the water the more accurate the GPS point will be and the deeper the less "pinpoint" accurate it will be because of the depth of water. While all this info is good to know, but I think we are over thinking here. The GPS does "almost" all of the work for us so we don't need to bring a calculator on the boat.

[Hickory Legend]

Thanks Mike,
I know this is all kinda trivial, I never run my water column that deep, and I use the cursor to mark and go look at objects closer.

Looking at the graph you have posted the little one with the vector lines. The way I understand it the range doesn't start until the graph shows bottom then goes out to the distance you have set.

On the picture you have I believe the distance to shore is correct, and the distance to the channel would also be correct but the 73 ft line would actually be 100 ft.

So without changing your range as you get deeper you are compressing the bottom view between the edge of the screen and bottom of the water column. This is shown on the understanding SI graph, where the distance between 1 and 4 on the bottom. as the water column gets deeper line one (the bottom ) pushes out towards the edge (line 4).

Going shallower on the same scale will spread out the bottom as the water column shrinks allowing more detail to be shown on the screen.

So on the screen you have the range selected + the water column.

Do you buy that.
Just board at work.

721 ProXP



Modified by 721 Pro XP at 7:06 AM 12/30/2010

[T Mike]

721, I totally understand what you are saying about the 73 supposed to be 100ft but thats not the way it works.

Picture this in your head. Your sitting in 102ft of water. Make your SI range 100ft to each side. What will you see? You will see NO lake bottom on your screen, but your beams are out 100ft so 100ft can't start when the bottom shows up because there is no bottom in this instance..... The water column counts as distance even though it's not horizontal distance (off to the side), (it's vertical distance under the boat).

[Wayne P.]

Mike, do you use Humviewer to look at recordings on a computer?

[Hickory Legend]

I totally understand what you are saying and also agree.

I was just going by this chart you threw up. From what the chart says line one and 4 are the same. Line 1 being from under the boat. Line 4 going out to the range set.




Heck with it I'm going fishing.

Thanks All
721 Pro XP

[T Mike]

721, Look at the graph I put up and find #1 in both. You doctored the photo wrong. 1 represents the depth and 4 represents the range in both parts on that image.

[Hickory Legend]

Ahhh so I see that now!!

So by looking at that and line 2, if you are in X ft of water nothing X ft out to the side of the boat is going to show up. What looks like it on the bottom of the lake is actually the water depth out to the side of the boat.

Maybe I have it now. If not I give up!!!!!

721 Pro XP