Basic Questions on DFF-3D For Navigation

[FWTMD]

New member, considering a Furuno package for a new build. The boat is a semi-displacement trawler that will operate generally at 6-8 knots. Home waters will be the Chesapeake, and travel the ICW, Bahamas, and up to New England. My interest is for navigation use only, and not fishing. As I compare the different electronics brands the personal bathy charts using a DFF-3D is a potential differentiator in favor of Furuno, but I am left with some basic questions that a review of some years of posts have not yielded answers.

1) Is use of TimeZero a MUST-HAVE, or can one build and use personal bathy charts without TZ? I am looking for simplicity, and additional software packages is more to manage, and pay for. Helm station space is at a premium and I won't be running a laptop or iPad too if at all avoidable.

2) With a use case of pure navigation, the point is to build detailed and up to date bottom data in shoal areas to avoid grounding. Depth differentiation and accuracy in deep water isn't valuable. It is in shallow water. How is depth handled with respect to tidal differences? Is there some adjustment made, or possible?

3) Is there any settings adjustment to dial in an angle from the mount not being 100% level?

4) How is depth adjustment for pitch and roll handled?

5) Can the transducer also be use simply to display basic depth on the MFD without the detail, or is a second transducer needed.

6) The boat has a full deep keel (draws 4 ft.), and any mounting location will have the angle to one side blocked. I presume I am going to get a one-side view and data collection, correct?

7) In shallow water, say 6 feet, what width of data collection can I expect, to the one side of the boat not blocked by the keel? I need to understand if its enough to become useful.

I likely have not thought of all important issues, so with that use case if there are other considerations I would love to hear them.

Thanks in advance for any assistance. Furuno has a lot to offer, and perhaps personal bathy charts is the game changer that tips the balance toward the brand.

 

[Johnny Electron]

If not concerned with fishing, I immediately wonder your interest in PBG. NOAA and C-map have more than enough navigational depth spot data to keep you in the clear. PGB is normally for someone looking for structure and fish. The units can be set to have the depth soundings turn RED for anyplace that your boat should be staying out of. Chart depth values are normally based on any low tides so that it is in the safe. While users should still have a good source of live depth to monitor live depth compared to charting, I don't think PBG should really even be a consideration for you.

 

[Quitsa]

Many years ago I had a cruising sailboat on the Chesapeake that had a draught of 5 feet. While I would normally think Johnny's point is sensible, in this case having had lots of personal experience with "surprise" shoaling not shown on NOAA charts, I can understand why the gentlemen is looking for another tool to get an extra layer of detail.

To answer your questions, you can build and save PBG charts using a TZT 3 display. There is no need to have a PC running TimeZero.

While the beam width of a DFF-3D is wide compared to a standard transducer, in very shallow water it is not going to show you much. Generally my experience is that the width of the area shown on the PBG or on the live bottom history mode is roughly twice the depth. So if the water is 6 feet deep, the DFF-ED will display the bottom out about 6 feet on each side from where it is mounted. In my case it is right on the keel and the beam of the boat is about 13 feet, which means that in water that shallow, the DFFF-3D is only showing what is actually under the boat.

As far as I know there is no compensation for tide. If you made a PBG at high tide and recorded a depth of 20 feet in a particular spot and the tide goes out 2 feet, the PBG will still show 20 feet.

The DFF-03D transducers have a built-in motion sensor and the display will compensate for heaving and pitch and roll. Even better is to have a satellite compass like an SCX-20, which will give more accurate compensation.

A DFF-3D can certainly be used to just display numerical depth values just like any other depth sounder.

I think I would come to the same conclusion as Johnny that a DFF-3D is probably not going to do what you want in an effective and consistent manner. It is great for what I need when fishing and trying to locate uncharted structure and be able to know what I am going over. But I am normally doing this in water that is 30-400 feet deep. I am getting a good wide swath of bottom. It doesn't matter to me if the tide is out and the water is 46 feet instead of 48 because what matters to me is the bottom contour. In shallow water, the width of the mapped area is just too small to be very useful even if you
don't mind the tidal variation.

The only thing I can suggest is to mount a 235Hz sounder (like the Airmar DST800 or the newer 810 as far forward as you can find a suitable location. The 235Hz frequency works well in shallow water and will respond quickly and precisely to changes in depth.

Having made these comments about the DFF-3D, there are other reasons to go with a Furuno system. In my mind probably the biggest differentiator is the radar performance. I have the new solid state DRS25A-NXT open array. It does an amazing job on small targets (like those millions of crab pots you have in the bay) if it is relatively calm. I have tracked thunderstorm cells almost 100 miles away. The automatic target tracking (ARPA) is a great safety if there are a lot of boats around.

 

[gtstang462002]

I can attest to the ability of the DRS25A-NXTs ability to track crabpots out in the Chesapeake bay. I regularly fish out of Solomons and love the ability to locate them when heading out before the sun comes up. I have also located working birds in the mouth of the Potomac as I come around Cedar point. That is almost 20 nautical miles away.

 

[FWTMD]

Thank you all for the detailed responses.

I feared as much, but hoped for better.

I quite agree Furuno has a lot to offer.

And thanks for the tip / review on the open array radar. I'll need a dome I think (space considerations).

Thanks again.

 

[Magnetron]

1) Is use of TimeZero a MUST-HAVE, or can one build and use personal bathy charts without TZ? I am looking for simplicity, and additional software packages is more to manage, and pay for. Helm station space is at a premium and I won't be running a laptop or iPad too if at all avoidable.

We do not require the use of Timzero Professional or Navigator on a PC in order to generate or use PBG with a TZ Touch 3. That said, PBG generated by the TZ3 can only be viewed by the TZ3/2BB and cannot be ported to a PC or other device other than a TZ3/2BB.

2) With a use case of pure navigation, the point is to build detailed and up to date bottom data in shoal areas to avoid grounding. Depth differentiation and accuracy in deep water isn't valuable. It is in shallow water. How is depth handled with respect to tidal differences? Is there some adjustment made, or possible?

If you take a scan at High Tide, and another scan at low tide the last scan made is what is saved.

3) Is there any settings adjustment to dial in an angle from the mount not being 100% level?

There are some adjustments that can be made to beam forming, but not for extreme gross angles if it was installed poorly. Note, installation is paramount to this product operating well.

4) How is depth adjustment for pitch and roll handled?

I would review section 3.3 on the Initial Settings portion of the manual.

5) Can the transducer also be use simply to display basic depth on the MFD without the detail, or is a second transducer needed.

Data such as depth, supplied from the DFF3D sounder, can be displayed in a databox on the left side of the screen.

6) The boat has a full deep keel (draws 4 ft.), and any mounting location will have the angle to one side blocked. I presume I am going to get a one-side view and data collection, correct?

This could be a big issue, and possibly affect the overall performance of this product. You should consult with a dealer or installer for an answer or send tech support photos of the hull and we could possibly make a recommendation.

7) In shallow water, say 6 feet, what width of data collection can I expect, to the one side of the boat not blocked by the keel? I need to understand if its enough to become useful.

It may produce data, but may not be very useful. @165kHz, the best performance for bottom mapping will usually start with at least a depth >20ft.

I hope some or all of this was helpful in anyway, :sail

- Maggy

 

[FWTMD]

Maggy:

Yes, extremely helpful and most appreciated. One value added for the brand would be the availability of this sort of support.

With the profile of my hull it certainly seems the utility of this feature for MY purposes would go from limited to very limited. The cost / benefit isn't there.

I am pleased to see TimeZero software isn't mandatory, which may come into play in other ways.

Interesting things are developing with transducers, but when one dives in the possible promise does not always pass the test. Some "other" brands offer forms of forward scanning sonar. However with the range being angle-limited, the actual usefulness seems limited. In waters where one can go from deep to a rock or coral outcropping, sure that can be terrific provided one has throttled down to seriously slow in order to provide enough time to avoid the spot. But in the gently sloping shallow water shoaling of the Chesapeake and ICW, not so much.

Good chart packages can only go so far, and can only be as good as the most recent survey.

My decision is made. I won't be pursuing this sonar technology.

The help received here has been quite valuable in working through this issue.

Thanks again.

 

[Magnetron]

Thanks for giving us a look, and your kind words about our support team. We encourage you to continue staying up with our company and exciting new products, as soon as we release them.

Best Regards, :sail

- Maggy

 

[mattology]

I have not been able to get PBG to work with any consistency in depths less than 20 feet. the dff3d will show in less depth than that, and the 3d sounder history works, but i usually just get missing multibeam data errors while trying to record pbg in anything shallower than 20 feet.