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Woodlander
Senior Member
Username: Woodlander
Post Number: 2184
Registered: 02-2003
| | Posted on Thursday, August 20, 2009 - 08:41 pm: | 
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Part VI
Fundamentals of Reading a Depth Finder
In order to successfully read what’s on the screen you need to know what your coverage areas is and it’s shape. The shape of the overall coverage area of a Lowrance is different than that of a Humminbird. Humminbird uses a cone throughout while Lowerance uses and cone for it’s central “cone” beam and then a bowl shape for the rest of the coverage. This makes their screen views different.
I’m going to go back to this picture but add the three balloons on the right. Now picture trolling up to the balloons and imaging which balloon would show up on the screen first and which one would be the last to be seen as you trolled away.
A good way to view a posted picture is to take a small square of heavy paper and cover the picture. Dragging the paper from left to right would give the same view you’d have in the boat.
It’s obvious from the shape of the blue viewing area that the top balloon would be seen first and last, and it is.
Now look at the central yellow cone. Again visualize trolling over the balloons to see which one comes in view first and stays in view the longest. Obviously it’s the bottom balloon this time.
Humminbird uses a cone throughout. This is a diagram of what the view is to me.
This is a picture going over the same balloons the same day. I’m using the 200/83 dual transducer with the new software with the chart speed on maximum. I used the default sensitivity of “10”.
I turned the sensitivity up because I think it gives the best representative picture of how Humminbird uses a wide cone.
Again I think it’s down to personal preference. In my opinion Humminbird gives a better detailed picture but Lowrance definitely covers more area. I’m going to stick with a Lowrance for most of the rest of this article because it’s the one I’ve use the most and have the most pictures.
As mentioned before the cone is 20 degrees. The diameter of the bottom of the cone is roughly 1/3rd of it’s depth. In other words if you were in 30 feet of water your cone would be picking up a bottom viewing area about 10 feet in diameter. How much is in this viewing area is dependant on the speed of the boat. If the boat was stationary the same viewing area would continue to be shown. If the boat was moving fast a lot of information would be compressed in the viewing area.
The most important part of the screen to watch is this area on the right that I’ve circled. The very first information of any significance that comes in is recorded on the far right where the arrow is pointing. Lowrance called it “FasTrack” for a while and it’s referred to on my unit as the “Amplitude Scope” on my “Sonar Features“ menu. It really a flasher like the very first depth finders use to record data. The only difference is that it’s now a vertical graph instead of the original circular ones.
Some companies still offer a “flasher” option with their newer units. This is a picture from my depth finder with the boat out of the water. I'll replace it with a real time one later but you get the idea.
When LCR’s - liquid crystal recorders - first came out not many good fishermen like them. The problem was the early processors used were slow compared to the flashers and so new information was slow to appear on the screen. Now there might be a second delay at 30 feet. You can test it by bouncing a lure off the bottom and watching the screen.
The problem with the Flasher/FasTrack is that the information can appear and be gone in a - flash. This picture shows the arrow pointing to all that’s seen of a lure dropping on the flasher.
The problem with flasher are that you have to pay close attention to them or you could miss an important piece of structure or fish. As the previous picture shows, within a split second, what appears on the flasher is recorded on the rest of the screen. It happens so fast that some might elect to just turn the flasher off.
The problem with the recorder is you have to get it in your head that it’s not a picture of what’s below. It’s a recording of how new information relates to old information. It’s also a recording of the distances that object are from the transducer at a precise moment.
Very few objects will remain at a constant distance from the transducer for any length of time. Either they are moving away from you or towards you, or you’re moving towards or away from them.
Next time you run into this I think it will make more sense.
I’ve got some more things to discuss before before I start posting examples of what you can see but I need some better pictures so I’ll wait until I can get them.
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Woodlander
Senior Member
Username: Woodlander
Post Number: 2187
Registered: 02-2003
| | Posted on Friday, August 21, 2009 - 06:41 am: |
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Those are bubbles coming up. They'll be everywhere in some places and on some days and really clutter the screen.
I'll have more on them later.
You are right about the fish on the right. I'll post plenty more later - in different degrees of activity - and they'll become obvious. |
Sodybread
Senior Member
Username: Sodybread
Post Number: 78
Registered: 01-2008
| | Posted on Saturday, August 22, 2009 - 07:46 am: |
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What Rand put an arrow on is what my baloons looked like only black and white.and the other things i marked. must been lots of bubbles the day i did my baloons |
Crawdaddy
Senior Member
Username: Crawdaddy
Post Number: 949
Registered: 02-2006
| | Posted on Monday, August 24, 2009 - 01:11 pm: |
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Good article Woodlander. Just to confirm what Lowrance and you called a flasher Hummingbird now call RTS or real time sonar?
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Rommel
Senior Member
Username: Rommel
Post Number: 100
Registered: 05-2009
| | Posted on Monday, August 24, 2009 - 06:43 pm: |
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Thanks, Woodlander. Taking your advice, I have decided to stick with black and white. I currently have a Lowrance X96 mounted in the console - 320 x 320. Using your instruction, I'm getting more out of that than I figured and decided to leave it there. I'm going to buy the black and white X135 for the front - 480 x480 and not have to worry about eye adjustments....thanks for bringing it to our attention the sometimes difficult transition from color to black and white! |
Rommel
Senior Member
Username: Rommel
Post Number: 122
Registered: 05-2009
| | Posted on Monday, October 05, 2009 - 04:50 pm: |
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Hey Doc - hope all is well. Wondering what your thoughts are on Hummingbird's new down imaging sonar? I've seen a few picturers posted and I have to say I'm amazed......let us know what you think. |
Spotsticker
New member
Username: Spotsticker
Post Number: 4
Registered: 06-2009
| | Posted on Friday, October 16, 2009 - 08:55 am: |
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I want to send out a special thanks to Woodlander. I have been fishing for 30 years and have never been able to catch fish on a spoon. The things I thought were fish were usually just trees or something else to get hung up on. To make a long story short my last trip out I caught 2 bass on a spoon. I was just fishing an area when I saw on my graph what Woodlander's pictures looked like. I dropped my spoon down and jigged it a few times and WHAM! Thanks again Woodlander for all of the time and effort. Now my graph is becoming more than just a depth and temperature gauge. |
