AIS questions

Alan Gomes

Sustaining Member
I sail out of L.A. Harbor (San Pedro), which is a commercial port with a ton of large shipping. I do not have radar but figured I should at least get AIS receive capability, especially for when the weather gets soupy in the shipping lanes.

I just installed a Standard Horizon GX2200 VHF radio, which also contains a built-in GPS, DSC, and AIS receiver. It seems to be working fine based on my quick test yesterday at the dock. It functions as a stand-alone AIS receiver with its own display for targets, or it can be interfaced easily with a chart plotter.

I have a couple of questions for those of you familiar with AIS.

(1) I'm wondering about what settings you might suggest for the CPA and TCPA alarms, particularly in light of the high density of AIS targets in L.A. Harbor. My thought is to set the CPA to something like 1 mile (with the CPA alarm off) and then set the TCPA to maybe 15 or 20 minutes (with the TCPA alarm set to "on" once I'm outside of the harbor). My reasoning--which may be faulty because I'm just now learning about this--is that if I set the CPA number too large I'm going to get a ton of hits. By setting it at 1 mile, or perhaps even 0.5 mile, it should cut down on that. But then having high enough number of minutes before it sets off the TCPA alarm would give me adequate time to alter course, ring up the ship if that were necessary for some reason, etc. I would not even turn on the TCPA alarm, though, until I was outside of the harbor, maybe a few miles past the L.A. Light. Just sitting in my slip yesterday there were an abundance of targets within half a mile of my boat! Many of these vessels were at the dock with their transponders on (SOG = 0.0). I wish the GX2200 could filter out the ones that are stationary, but it does not appear that this is possible. Once I get outside of the breakwater a ways that should clear things up.

(2) My GPS is a Garmin 546S. It has a 5" screen. I can easily interface this unit with the GX2200 in order to show the AIS targets on the chart. However, I wonder whether this might actually be counterproductive. 5" is a small screen and it seems as though I'd have lots of little triangles clogging the display much of the time. More to the point, I'm not sure how valuable seeing the targets on the plotter would be vs. the display on the radio anyway. I'm thinking that the main thing is having the TCPA alarm alert me, which I can easily hear from the cockpit. If it goes off, a quick look at the GX2200 display will show me where the ship is relative to me. Any of the calling functions, should I choose to use them, would be done from the radio anyway. I may go ahead and wire it up to the Garmin just to see what I think, but if there is a strong consensus otherwise I might forego that.

Thanks for enlightening me on this new-to-me technology.
 

toddster

Curator of Broken Parts
Blogs Author
I've had to turn off the AIS alarms on my chartplotter. With the result that I get an alarm saying that the alarms are off. :rolleyes:
The reason is that, although the number of targets in my home area is small, since it's a river (basically all "harbor") every one of them trips the "dangerous target" criteria. Every single vessel coming up the channel will have an intersecting course at some point. It gets really annoying having to silence the alarms every 30 seconds, when you are actually doing a tricky bit of sailing to stay out of the way of that commercial vessel. And my slip is close enough to the commercial dock that I couldn't find a setting that wouldn't alarm in the marina.

Dunno about your Garmin. Maybe depends on the size of the target symbol displayed? Sometimes that can be adjusted. I find that even the tiny display on the Standard Horizon RAM mic is surprisingly useful, as long as there aren't more than about four targets. Well, it lets me know that someone is out there and in which direction, anyway. My chartplotter has a 7-inch screen and the AIS and radar overlays are not a problem. The overlays are also semi-transparent, so you can see chart features behind them.
 

woolamaloo

Member III
Alan,

I also dipped my toe into AIS with the Standard Horizon GX2200. I absolutely love it. I believe that it's the cheapest and easiest way to add AIS reception. I installed the RAM3 remote mic so I have the display at the helm since most of my sailing is single-handed; I just couldn't duck below to stop the CPA alarms. Like toddster, I've found the CPA alarms to mostly a nuisance. I've taken to only using them when I'm sailing at night in the shipping lanes on the Great Lakes. But sailing back to Cleveland, it will alarm every few minutes. It can be maddening. I wish there was a way to select individual ships and mute the alarm for that ship. That tug moored up the Cuyahoga River is not going to run me down.

I did interface the NMEA signal to my 7" Raymarine Axiom chartplotter. Unfortunately, the GX2200 is NMEA 0183 and the Raymarine is SeaTalk. I used the Actisense NGW-1-STNG NMEA Gateway. I had to flash new firmware into the Actisense device and solder all those tiny connections together. It was a fiddly project but it works great. Hopefully, connecting to your Garmin will be simpler. Now, I rarely look at the AIS on the GX2200. There's so much more information on the chartplotter. My display is a bit bigger than yours but I've found that most of the time, the AIS triangles don't cause too much visual interference when entering a port. (Cleveland is one of the busiest ports on the Great Lakes but it's not L.A.) I customized a screen on the chartplotter that leaves the AIS info off. I can switch back and forth if I need to.
 

Alan Gomes

Sustaining Member
Thanks, Jim. Your information (and Todd's) is helpful.

My Garmin 546S has both NMEA 0183 and NMEA 2000 connections. I'll use the NMEA 0183. The wiring itself should be trivial, but running the wires for a permanent installation will take up most of the time. I also usually single hand, so that is an argument in favor of having the info at the helm. I have a good autopilot, though, but I may find that I'll appreciate having the info right there. I'll just have to try it to see how clogged the 5" display gets.
 

Alan Gomes

Sustaining Member
Like toddster, I've found the CPA alarms to mostly a nuisance.
Here's a follow up question on that point. I can see where the CPA alarm by itself would be a nuisance. If I were to set the radius too low to avoid all the excess hits, it wouldn't give me time to respond. But if I were to set the radius too large, then it goes off all of the time. But how about relying on the TCPA alarm? My thought was to set the CPA range low (half a mile to a mile maybe) and the TCPA time relatively high (say, 20 minutes). That way, unless a vessel is going to get close to me within 20 minutes the alarm won't go off.

Thoughts?
 

woolamaloo

Member III
Seems logical. I wish I would have thought of it first. I'll try it when my boat is back in the water. (50 more days)
 

debonAir

Member III
The problem with CPA is that, on a sailboat, you're slow and your course is changing all the time. I found the alarms to be useless as well because any reasonable settings give you too many false positives and any restricted settings are essentially "too late to do anything about it besides pray".

For those reasons I decided that it would be better to give than receive and got a Vesper 850 AIS transponder. This way, the large fast power vessels can see and avoid me vs. me trying to scoot out of the way at 2kts. Even if they can't steer out of the way they can at least hail me on VHF if needed.

The unit also has an anchor alarm that uses its built in GPS which is handy and comforting at night. I'm super happy with it and highly recommend the company.
 

Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
I have all alarms off on inshore waters. If crossing shipping lanes in fog my eyeballs are very interested in the AIS screen and the CPA of approacing vessels.

To my mind, alarms are for sleeping.
 

Alan Gomes

Sustaining Member
Thanks, gents, for the advice that comes from your practical experience.

It still seems to me that the issues debonAir has raised ought not to apply to a TCPA (not CPA) alarm used as I'm suggesting. If I have, say, 20-30 minutes to adjust my course to avoid a large ship, even my slow-coach E26 at 5 knots should be able to put adequate distance between myself and one of those behemoths. I'll just have to experiment a bit to see how it works in practical life, in situations with plenty of visibility. Then, when conditions get thick, I'll have some confidence.

A transponder would no doubt be superior to what I've got. However, if I wanted to contact a ship that seemed to pose a threat, the GX2200 makes it very easy to contact AIS targets via DSC. I think I'd prefer to initiate the contact rather than hoping someone on the bridge would take the initiative.

Alarm or no alarm, I'm also convinced by this feedback that I really should wire this up to the chart plotter. I plan to do that at my first opportunity. The wiring as such is trivial. Snaking the wires is the most significant part of the job, but not terrible.
 

footrope

Contributing Partner
Blogs Author
I have all alarms off on inshore waters. If crossing shipping lanes in fog my eyeballs are very interested in the AIS screen and the CPA of approacing vessels.

To my mind, alarms are for sleeping.
Agree. I, too, wish non-moving AIS targets would be ignored for alarms unless I was headed for them. I also wish folks would not leave their transponders on while parked in a marina, or when hauled out.
 

Alan Gomes

Sustaining Member
I got down to the boat yesterday and wired my GX2200 into my Garmin 546S. It was very simple to do. As I figured, being in L.A. Harbor there are a massive amount of targets within a mile from my slip that clog the display. Nevertheless, I can already tell that wiring this into the chartplotter was the way to go vs. using the GX2200 by itself. And yes, I've got the alarms turned off--for now. I may enable them out in the channel but the display by itself may be all I'll need.

I really don't understand why there is not a setting to filter out stationary AIS targets. This should be trivial to add in the software and would greatly help in heavy shipping areas like L.A. Harbor.

Thanks again for all the good advice.
 

debonAir

Member III
"I really don't understand why there is not a setting to filter out stationary AIS targets". Guess it depends on who's going to do the colliding part. In the fog, the stationary targets are just as easy to hit as the moving ones :) It would be nice to have some levels of color/blink highlighting where the more likely problems are more visibly frightening.
 

Alan Gomes

Sustaining Member
"I really don't understand why there is not a setting to filter out stationary AIS targets". Guess it depends on who's going to do the colliding part. In the fog, the stationary targets are just as easy to hit as the moving ones :) It would be nice to have some levels of color/blink highlighting where the more likely problems are more visibly frightening.
You do have a point there. Large commercial ships are not going to be stationary in the shipping lanes (at leave I've never, ever seen that), though there is not really the congestion once I'm out there anyway.

The Garmin does color what are called "Dangerous" targets in red. The non-threatening ones show up green.
 

Parrothead

Member II
I really don't understand why there is not a setting to filter out stationary AIS targets. This should be trivial to add in the software and would greatly help in heavy shipping areas like L.A. Harbor.
Alan, did I mention iNavX does exactly that? There is a button that allows you to choose U/Way (Underway) only. Other options are All, Class A or Class B targets.

I agree with you that if iNavX can do it, everybody should be able as well.
 

Alan Gomes

Sustaining Member
Alan, did I mention iNavX does exactly that? There is a button that allows you to choose U/Way (Underway) only. Other options are All, Class A or Class B targets.

I agree with you that if iNavX can do it, everybody should be able as well.
Yes, you did mention it to me. Not sure why Garmin chose to omit it.
 

Alan Gomes

Sustaining Member
Have you tried contacting Garmin?
No.

It definitely lacks the feature, so if I did call them it would be simply to suggest they add it. My unit is pretty old so I wouldn't hold my breath for an upgrade even if they were to add it down the line to their newer units. Firmware updates for my model ceased some time ago.
 

Alan Gomes

Sustaining Member
No.

It definitely lacks the feature, so if I did call them it would be simply to suggest they add it. My unit is pretty old so I wouldn't hold my breath for an upgrade even if they were to add it down the line to their newer units. Firmware updates for my model ceased some time ago.
For that matter, the GX2200 lacks this filter on its display as well.
 

Christian Williams

E381 - Los Angeles
Moderator
Blogs Author
Well, fellas, my route to Catalina goes through what are often two or three very large moored tugs. They're tenders to the tankers that moor off Dockweiller. There's usually a tanker too. They're all swinging from enormous buoys for days at a time.

Threading through there in morning fog I'm pretty glad they're blasting their AIS signal. Really helps since I don't have radar.
 

Alan Gomes

Sustaining Member
Well, fellas, my route to Catalina goes through what are often two or three very large moored tugs. They're tenders to the tankers that moor off Dockweiller. There's usually a tanker too. They're all swinging from enormous buoys for days at a time.

Threading through there in morning fog I'm pretty glad they're blasting their AIS signal. Really helps since I don't have radar.
Well, there's nothing like that on my route to Catalina--at least not until there is.

Your point is well taken.
 
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