DFF3d dropping one side

[jessembowen]

The port side of my DFF3d is dropping the edge of its scan down by as much as 3 to 5 feet.

I have tried adjusting the roll offset to correct this, but have not had any luck with the settings.

I have tried small number increments, and then tried stepping it all the way to 45 with no discernible change. I have also tried this for the "negative" side as well.
(I have tried 1, 3, 5, 10, 15, 45 and then negative)

I have noticed this converts to a degree when input.



I currently run the following
TZ2
dff1-uhd (using tm265)
dff3d (165T-B54 thru hull)
sc30
Fi5002 (furuno nema junction)
hub

I record the scanned data using Nobeltec TimeZero Pro 3.
Previously I collected data only from the TM265, but can now record the DFF3d after the latest update/add-on.

However, the drop down is corrupting all of the scanned data, creating data points that are actually lower than possible, and when the low point crosses previously good data, it corrupts that as well.

I am ending up with area's that should be flat, but look like they are scooped out, or deep on one side.

I had the transducer professionally installed and hope that it is not an issue with the physical transducer. Any help on this would be appreciated.

Here I start a scan of an area (notice the 90/92 area in red box)


When I turn if you notice the deep area, in the 90's, this is from the drop down on one side.

 

[Snips]

Jessembowen,
Really hard to tell much from your screen shots. Personally I find looking at the section view easier to look at when trying to determine a flat bottom. Also when you are trying to set up the DFF3D start with a fresh database and not trying to add to an existing one. But lets first start with your SC-30, did you zero out the pitch/roll offsets at the dock? Did you measure the vessel for the XYZ offsets? In looking at you data it looks like their is a hump in the center, if the track is convex or concaved you need to flatten the it with the Sound Speed Correction control. Are you sure the transducer is facing forward and not aft? If the transducer was facing the backward this would make the roll correction backwards also thus making the bottom look like a ruffles potato chip.

Snips

 

[jessembowen]

Snips, Thanks for the reply.

On the first picture, I was referring to the blue colored "ground" on the far left side of the screen. The "structure" in the middle was legitimate.

I guess my issue got lost in my wording somehow.

With the two pictures at the bottom of the post.
This is very flat bottom and did not have 86 to 90 (a 4 foot drop) on it.
This should have been 85 to 88 max, with no 90 foot markings.
The fake drop is caused only on one side of the scan line, it appears on the tz2, as deeper sections (and is captured on my nobeltec as 90 foot markings, which do not exist)

This is a typical example of the type of dff3d scan I am getting:

This should also be a fairly flat area.
However if you follow along the left side of the scan/track, you will notice it drops down to a deeper depth on one side. This happens on ALL of my dff3d tracks, no matter the depth. Always on the port side.

The invalid data is occurring on the dff3d data, I just don't know how to correct it.
I did not install the transducer, but I am pretty sure it is facing the correct direction.
The torsion bolt it toward the bow.

My pitch/roll offsets are currently set at 0, however, How do I zero out the pitch/roll offsets at the dock? (You might be referring to a different calibration I am not aware of?)

I do have XYZ offsets in, you mean for the distances between the center of gravity and other components, correct? however there are in as feet. How exact do the measurements need to be? Is 10 feet as and example (10.0) ok, or does it need to be specific to inches for each (10.375)measurement.

I thought the speed sound control was a just a salt water setting, (essentially a on for salt, off for fresh). I looked up the setting and saw it can range from -220 to +200, what should it be set for (or the ranges), It should already be configured for salt, but I will have to look at the setting.

If I need a roll correction to the port side, (will that be a positive or negative number) and can you recommend how big or small this number should be.

Thanks for the assistance!

 

[Snips]

Jessembowen,
Using the sectional view a flat bottom should appear like below. The Sound Speed Correction compensates for the water temperature and is very different than the Fresh/Salt setting. Using the sectional view vary the setting from -200 to +200 and watch how it will bend the bottom return. Also know that the shape of the transducer itself symmetrical and can be reversed within the fairing.

Snips

 

[jessembowen]

Snips,

Thanks for the information.

I did not realize the transducer could still be mounted wrong if the fairing was correct.
(I thought it was shape based, and would only fit one way).
Does the DFF3d show correctly on the TZ2 if it is reversed? (How is the best way to tell what the correct setting is). It sounds like you are saying it WILL work both ways, but one way will give the pringle type data returns. (Which I think I have)

I will change the "speed of sound" setting and test that out. I know I have a "bubble" in the middle there, so this would be good.

Are there any other changes or settings that I can test. I don't live near where the boat is stored and it is a 6 hour drive, one way. As much as I can knock out or test would be great.

This is why I was asking about the specificity of the XYZ numbers, and the roll offset, if those need to be changed.

Thanks for your help on this!

 

[Snips]

Jessembowen,
I reconfirmed that the transducer can fit into the fairing both ways. The transducer does have a Bow arrow on the top and if you are looking at the bottom the temperature sensor is aft. If the transducer is backwards you a check the Transducer Mis-mount Correction box in the transducer setup menu. While the XYZ offsets are important they won't make the bottom on one side appear lower.

Snips

 

[flowmotion]

Jessembowen,
I have the same setup as you (transducers, sounder boxes and TZ software) with the exception of the SC30.

I am just starting to test it out. I initially noticed drop offs on both sides. They don't appear to be there now. When I get settled down I will post some results.

 

[flowmotion]

Jessembowen,
Here are some photos of a scan of a wreck I just made.
It does not appear to have a drop off on one side or the other.
There are ripples as the roll adjustment is not compensating for sea conditions.

Here is a video of the same area: https://youtu.be/VNoITzqyUiU

 

[flowmotion]

Additional screen shots. It appears that the shallowest readings are always directly under the boat.

 

[jessembowen]

Flow, it appears you had better luck getting out than I did on 5/6.
I was not able to get out at all, but I was able to do some dock and bay testing.

My issue appears to be the sound speed correction.
I also verified that the transducer is not miss-mounted (thankfully!)
I believe the sound speed correction was set at the default of 0, after testing the numbers in both directions, I ended up using a +65 setting.
I can visibly see the edges of the dff3d scan (and round hump in the middle) go up and down (concave, convex or flat) as the number is changed accordingly.

At the dock, I also noticed I was having a permanent roll issue, I was able to use the roll offset to correct this (I think I added a -2.3 degree to this). at the dock (which was calm) I now show a minimal roll amount.

I did not change the pitch amount as my boat sits heavy to the stern, and I believe the numbers shown are correct.

It was quite rough in the afternoon so I was not able to do any real deep water testing. The bay has a small 50 foot deep section that allows me to do limited dff3d tests. I hope to verify that the problem is corrected on the next calmer day.

 

[flowmotion]

Jess,
I will try those parameters soon. The sound speed may remove the artificial peak I get under the boat. I may not need to adjust the roll. I gather that fixed your one side drop. Thank you for the tips!