Amazing radar trick for crab/lobster pots

OK, I'm going to feel dumb if almost everyone knows this, but I recently worked with a radar setting that let me get through 500-700 crab pots with phenomenal ease - at night! I was making a fair number of turns, but saw every single pot on the radar as a huge red blob and just eased on past them, usually between two of them at a time, with not a single hit. And, it was pitch dark. With a hand held spotlight we could see the pots, but not usually until they were alongside and maybe ten to fifteen feet away.



It was not me who "done it". It was a good friend who is very, very adept at going in and making settings to radar and all things electronic. We saved the profile as "Crab pots" under our Radar settings, so I can call it back up whenever I need it and he isn't around.


I don't know how many people would be interested in this, if any. If you are interested, let me know below, in open forum, and I will make sure I'm getting it to you just right after reviewing with my friend, and make it more public knowledge.


If I don't get people interested - well, it means I was the only one who didn't know. Doesn't surprise me.

Um, ........yeah! Never enough learning going on for me.....

I am always interested in learning something new. Most pots around here are just a styrofoam float, don’t know if my old radar would pick them up or not. Have seen birds and airplanes. Nice boat you have, by the way.

On my 2013-ish Raymaine 4kw HD solid state unit I have a buoy setting. Work ok for that. I will try it on the next crab pot I see in the PNW. I don’t hold out much hope.

I'm definitely interested! I can't fathom how my radar will be able to turn those tiny sticks into "huge red blobs". But then again, I'm still a radar neanderthal.

I'm in for any info. I posted in the other thread.


Dungeness crab pots are ubiquitous in the Puget Sound in the summer months, both commercial & rec.

I am interested! I don’t do night passages, but I do go out in fog....

We are always interested. Couple questions, newer boat, so I assume you have a solid state radar? What brand and type? I can see pots with a newer Gen Simrad 4G, and now with a Furono NXT, but I couldn’t see them with an older gen Raymarine open array magnetron system. It may be more about your gear and it’s capability, then the settings.

What chart plotter and radar unit are you using?

When I last tried to use my radar, before the season ended, it wasn't coming up. If it's dead this Spring I may have to start looking for a replacement...

Yes, interested for sure

In my experience with lobster buoys, they only show up when it's pretty near flat calm, and then only if they're wet. You sometimes can tweak until you see some of them, and every once in a while the stars align and you can see most of them. But of course there's always those few sitting just below the surface.

I'm skeptical other than flat calm conditions. If they really show up as a big red blob, in Maine the screen would be solid red.

Fishermen use line that floats and pots may have much more line on them than the depth. Fishermen rarely change the lines for different depths, so there could be lots of floating line near the buoy. Once the pot's been on the bottom for awhile, the line might stretch out depending on the sea conditions.
It's a good idea to miss the buoy by 100 yards or so.

I have an email in to my electronics guru/friend/shipmate. Basically, the sea state was only 1-2 foot waves, and I do not expect I would have seen any beneath the surface. I don't know if I saw them all, but we did not hit any. I was not exaggerating when I say we passed through 500+ crabs pots, and it was kinda fun once we (I) had figured out how the pots were going to appear on the screen. It is a Garmin, about 3 years old. What I do remember, and I will be getting more info when Paul returns my email or calls, is we had to set the radar range for just 1/16th of a mile, with the second ring obviously then showing 1/8th mile, so the pots came up quickly, but since we were only cruising at 7 knots it was not a problem, although you had to keep your eyes checking the radar every few seconds. The pots TRULY appeared as very large, red blobs. I've been on the open ocean and cruise ships did not appear as large although, of course, I was not getting to within 1/16th of a mile of them. I also remember you get all the sea birds flying across the screen regularly, but they don't look anywhere like the pots. Navigating involved a lot of twisting and turning to go between pots. The pots were typically in strings of 6 or so and, also of course, you only needed to get between any two to cross the string, unless you were approaching the string head on, in which case you needed to pass through the first two and then possibly a couple more before you realized what was going on. The night was pitch black. There was some moon, but not much. We could see MOST of the pots when they were abeam on one side or the other and they were within a few feet. I'll post the parameters he fed into the radar when he gets back to me. He travels a lot, so maybe I'll send him a second email asking for a quick call or response within a day or two.

“It's a good idea to miss the buoy by 100 yards or so.”
In Maine there could be 500 pots in a 100 yard zone.

To clarify, I can only see them in near flat conditions and with the scale dialed in close, say 1/8 to 1/4 mile. I still think the type of radar you are using As I posted earlier is the key here.

Definitely interested! Heading back up to down-east Maine this summer.

We don't have lobster floats but do have prawn and crab floats and of course logging debris so I too would be interested.

Put me on the "interested" list. Crab traps are a PIA in some areas of the Gulf. If you have the data would be nice to know the horizontal beam angle of your antenna. My boat puts her nose up pretty high depending on cruise speed - I'm working on an adjustable mount that will let me tilt the plane up or down a few deg for max response on the fly - mostly looking for river trash/logs/deadheads in the fog.

If calm water, almost any radar later than 2010 vintage and the earlier Raymarine Pathfinders would show the pots (even smaller crab floats).

They would be a blob if the gain was turned all the way up on low range and the radar tilted down enough.

Make sure the other filters were turned off such as rain and sea clutter, etc.

Include me as interested!

OK, so here is my guru's answer. First, he reminded me that he is a Master Captain and was a Coxswain on a Coast Guard boat long ago. Most importantly though he is my friend.


By the way PSNEELD pretty much nailed it.


I quote from my friend, Master Captain Paul S.:


"85% gain, zero sea state, zero rain clutter, pulse expansion on or off as best shows targets...tune gain to highest setting that does not cause interference returns (messy screen). Range is on absolute shortest setting (1/16th mile with 1/32nd mile range ring" "Best solution calls for radone to be aimed lower than parallel to sea surface - some mounts let you change this angle easily when needed...Open arrays have a much tighter beam and therefore have a tougher time seeing pots if not aimed downward. Enclosed domes work much better."


And so, there it is. All I can say is that my boat has Garmin stuff including an enclosed radome, the radome did NOT need or get any physical adjustment - just the settings Paul talks about, and the "huge blobs" I now realize was because of the "pulse expansion", but that worked wonderfully. And, we navigated several hundred pots without any hits, and it was a dark night.


It was great. I will be navigating the East Coast for the next several years, or until I drop dead, whichever comes first. I will often be in lobster pot territory (and I guess crab pots too - that is what I was in going from Ft. Myers on a straight line to Key West), and I will have the confidence to not worry if I need to get through the pots late at night, or in the fog. Nantucket and Bar Harbour here I come...Medic

Good onfo especially for us radar newbies.


THank you

and to PSNeeld also.

C lectric said:

Good onfo especially for us radar newbies.


THank you

and to PSNeeld also.

Click to expand...

Thank you...comes from thousands of hours towing at 2-5 knots and being so bored you play with electronics like they were today's smart phones and turned the VHF radio to the WX channel computerized voice report just for company.


Maybe now people understand when I say I don't have my radar on all the time when I run my trawler....

Thanks. I'll mess with it in good weather and see how lucky I get. Better then, than when it's pea soup.

That must be newer solid state radar. On my older pulse radar, the Main Bang eats up 1/2 of the lowest range so anything closer is unreadable. I'll give my newer Garmin XHD a try next time out.

High Wire said:

That must be newer solid state radar. On my older pulse radar, the Main Bang eats up 1/2 of the lowest range so anything closer is unreadable.

Click to expand...

That is why you set the pulse length as short as possible. My 10 year old Furuno does that automatically on short range settings. And if I zoom in the range (but even 1/4 or 1/2 mile is fine, though I do have large displays), increase the gain and turn off all of the auto adjust (sea state, clutter, etc.), I can see lobster hoop floats (presumably the west coast equivalent), though due to the height of my antennas, I can't see closer than about 60' in front of the boat.

Folks,

I hate to disappoint, but, unless one can control the seas, and I don't think Garmin has that button on their radar panel, there is no possible trick here (.) It is that simple.

In fair seas, where the pots are above the water, they can be seen. In particularly calm seas, if they are consistently above nearby water with respect to the radar lines of site, they can be seen consistently. If they can be seen consistently, one can reduce radar range to make them appear larger on screen, and use things like target expansion to make them, as stable contacts, appear larger than their reflection. In calm seas, one can also turn up gain a lot more, to see smaller contacts, as the smaller contacts are more likely to be signal than noise.

But, as soon as the sea state becomes a little rougher, the buoy contacts will appear and disappear behind the water. If there is just a little bit of this, the buoy contacts may be stable enough, so one can add a little bit of filtering of "sea clutter" and possibly still see buoys. But, inevitably, some of the weaker buoy contacts will disappear among the filtered unstable "clutter". Depending upon the seas, target expansion may still be helpful.

As the seas get rougher there starts to be a thresholding problem where contacts, both noise and signal, come and go as a whole as one adjusts filtering. More sea clutter filtering is needed, so actual contacts, small and unstable as they may be, are lost with the noise. Some buoys may still be seen, because they may large and floating high, and more likely to be more stable on the screen than the seas, so expansion may still help some, for some.

But, more and more the buoys will blend into the seas. Increased gain will increase noise more so than actual contacts, and will appear stronger on radar. The buoys will spend more time in larger troughs, so they'll not only become relatively weaker, but also less stable and less enhanceable.

The end result as the noise level increases and the sea level has higher peaks and deeper troughs with a smaller periodicity is that smaller contacts become relatively much smaller and less stable than the noise. One can't enhance what one can't separate.

It is possible that, if there is a large, densely trapped area of water, the large number of buoys, together, will generate an area that can be separated from surrounding water longer than individual buoys can be seen -- but that may not help much, depending upon this situation and goal, and even then is only a thing within a limited window of conditions.

Some days, I've been able to pick out a single bird sitting on the water or a dolphin or seal ahead. But, those days aren't super common.

Given the small size of trap buoys, in anything but really great seas, they can't reliably be seen (.)

Proceed with caution, at a reasonable speed for conditions, keep a careful watch, and be prepared to respond at the helm. Depending upon where and when one is boating, one might want to stick to marked commercial channels when visibility is limited.

Coming back from Catalina to LA at night in rough seas, I'd often stick to the commercial channel to ensure that I stayed out of trap fields. Of course, there still could be a drifter. And, bizarrely enough to me, I more that once full stopped over a mylar balloon!

Medic, thanks for the tip and details. And to gkesden for expanding on the limitations. We boat mostly on inland rivers in the southeast - fog, tows, small fishing boats, and trash are our major concerns. Will report how the new GMR HD 18 does looking "in close" at small targets as soon as I finish the install and head north for the summer.

Aren't there regulations to limit such hazards? Perhaps there is a need for "mine" sweepers to eliminate them.