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Old 08-06-2014, 10:53   #61
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Re: Thoughts about AIS

Quote:
Originally Posted by Dockhead View Post
All AIS displays give you the CPA That's not what we were talking about.
I thought that was what you were missing? Is it the vectors to tell you if it was in front or behind you then?
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Old 08-06-2014, 11:05   #62
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Re: Thoughts about AIS

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Originally Posted by hoppy View Post
I thought that was what you were missing? Is it the vectors to tell you if it was in front or behind you then?
We were talking about the dynamic of the bearing to target. Whether the target bearing is increasing or decreasing, so that you can tell whether the target is passing ahead or behind of you. The way we used to do it with hand bearing compasses (or with radar) before AIS.

Some others on here pointed out that OpenCPN and also Vesper show with dots on the chart where your vessel will be, and where the other vessel will be, at CPA. That fulfills the same purpose as my suggestion that dynamics of the bearings be displayed. And indeed fulfills it better. I liked it and lamented that chart plotters don't show any of this.

If you read through the thread from the beginning, you'll get all that
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Old 08-06-2014, 11:22   #63
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Re: Thoughts about AIS

the other method I use sometimes is turn 10 degrees to port or starboard and see if the CPA increases or decreases. Not a great last minute tactic though as the target might think wtf is that guy doing??!
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Old 08-06-2014, 11:53   #64
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Re: Thoughts about AIS

Quote:
Originally Posted by Dockhead View Post
We were talking about the dynamic of the bearing to target. Whether the target bearing is increasing or decreasing, so that you can tell whether the target is passing ahead or behind of you. The way we used to do it with hand bearing compasses (or with radar) before AIS.

Some others on here pointed out that OpenCPN and also Vesper show with dots on the chart where your vessel will be, and where the other vessel will be, at CPA. That fulfills the same purpose as my suggestion that dynamics of the bearings be displayed. And indeed fulfills it better. I liked it and lamented that chart plotters don't show any of this.

If you read through the thread from the beginning, you'll get all that
I did read from the beginning, but that was a when it was on the first page or two still and forgot

With my Raymarine I could tell whether the CPA was in front or behind from the way the vectors were displayed.

I can't remember exactly how clearly it was displayed as it is so long since I have been on board.

Last year I could tell a ferry was going to pass close behind me and for the sake of it I changed my course so that they would pass further behind. However the ferry clearly saw my course change on their AIS and changed their course reducing the CPA to the original amount.
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Old 08-06-2014, 12:40   #65
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Re: Thoughts about AIS

Dockhead,
Wow, did this discussion take off...(and I haven't read all of the posts...sorry!)
But, I do think I can contribute some concise info and experienced comments...


1) As others have mentioned:
- How AIS targets are displayed...
- How AIS target CPA is displayed, and how effective (or ineffective) your unit is in showing your crossing situation...
- How effective radar targets are tracked...(ARPA and/or MARPA)...
Are all mainly a function of your display(s) and its software, including the radar software (for MARPA)...
{I still can't figure out why anyone buys any AIS display, but a Vesper....but, oh well....that's for further down the page... }


Quote:
Originally Posted by Dockhead View Post
AIS revolutionizes the way you get through areas of dense traffic, but I have some complaints about how the information is displayed on my Zeus system.

The main problem is that you have no good way of determining whether a target is passing ahead or behind. This information is crucial in determining what kind of maneuver you need to make in order to create a safe crossing with the target.

In areas of dense traffic where it was necessary to track multiple targets at once, I found it impossible to do from the helm. I left my crew at the helm and retired to the nav table with a good old fashioned pencil and paper, and started writing down bearing, range, and CPA at regular intervals. This is really inefficient, and it is frustrating because it would be totally simple to present this data electronically.
2) As others have mentioned the Vesper Marine products do a WONDEFUL job of displaying the AIS targets and providing a "CPA" display screen that shows quickly and effectively what your crossing situation is (for any target).

The Vesper Watchmates (the 650 display, the 750 receiver, and the 850 Class B transponder), as well as their Vision system, all have a "CPA" display page, which is a very nice, and very quick and effective way to easily SEE where/how your crossing situation will occur...
It shows exactly WHERE the other vessel will be at your CPA, as well as showing the exact CPA distance and time...

This is the Watchmate CPA display (monochrome), the Vision is of course full-color (and higher res)...
Quote:
WatchMate is not the first AIS plotter to graphically illustrate what a particular CPA will look like. Again, why hasn't this view proliferated? While it's great to know with some certainty that if you and another vessel maintain course and speed the Closest Point of Approach will be, say, 1/4 mile in 12 minutes, you still may not know if that means you'll be crossing the bow of big, fast ship -- yike! -- or nicely passing astern. This screen instantly gives you the answer and moreover will change in real time if you or the target change course or speed.




And, here is the target info page...




And, here is the default AIS page....



I'm showing these display pages (above) in reverse order...

The best advise I can give you, is to buy a Vesper Watchmate 650 display for your helm position....(and maybe even one for the Nav Station)...
Once you use it, you'll wonder why in the world everybody else's AIS displays aren't the same way!!!


Have a look at the Panbo article on the Vesper units....
http://www.panbo.com/archives/2013/06/vesper_marine_watchmate_still_the_leader_in_ais_co llision_avoidance.html


And, the Vesper pages...
http://www.vespermarine.com/


I could ramble on, but I think the above links and photos will give you most of the "AIS" answers...





3) As for MARPA, ARPA....
Yes, MARPA is "Mini-Automatic Radar Plotting Aid" and (as others have mentioned) is a Non-IMO compliant ARPA...

Not sure why the Zeus system isn't automatic, nor why it is limited to a few (max 10?) targets....
But again, that is system/platform specific....

As for the bemoan from some on the internet that "MARPA sucks", etc., here again, this is also system/platform specific (requiring decent software and system design) as well as requiring "fast heading sensors", etc.

Is AIS superior to MARPA for accuracy and conveying the CPA's, etc....
Yes, of course it is...
But of course, not everything floating, or surrounding us on the water, has an AIS transponder....so keeping a good watch, and use of radar (and MARPA as needed), will still be necessary for a long time to come!!!




4) To sum up...
I think most have the same reaction to having AIS on-board as you did...
It is a GREAT tool to have...

But, I think most (all) of your negative observations are Navico / Zeus issues, which are not present with my Raymarine system, nor with my Vesper Watchmate...




I hope this basic info and these brief comments, are helpful...



Fair winds..

John
s/v Annie Laurie
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Old 08-06-2014, 13:03   #66
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Re: Thoughts about AIS

Quote:
Originally Posted by ka4wja View Post
Dockhead,
Wow, did this discussion take off...(and I haven't read all of the posts...sorry!)
But, I do think I can contribute some concise info and experienced comments...


1) As others have mentioned:
- How AIS targets are displayed...
- How AIS target CPA is displayed, and how effective (or ineffective) your unit is in showing your crossing situation...
- How effective radar targets are tracked...(ARPA and/or MARPA)...
Are all mainly a function of your display(s) and its software, including the radar software (for MARPA)...
{I still can't figure out why anyone buys any AIS display, but a Vesper....but, oh well....that's for further down the page... }


2) As others have mentioned the Vesper Marine products do a WONDEFUL job of displaying the AIS targets and providing a "CPA" display screen that shows quickly and effectively what your crossing situation is (for any target).

The Vesper Watchmates (the 650 display, the 750 receiver, and the 850 Class B transponder), as well as their Vision system, all have a "CPA" display page, which is a very nice, and very quick and effective way to easily SEE where/how your crossing situation will occur...
It shows exactly WHERE the other vessel will be at your CPA, as well as showing the exact CPA distance and time...

This is the Watchmate CPA display (monochrome), the Vision is of course full-color (and higher res)...





And, here is the target info page...




And, here is the default AIS page....



I'm showing these display pages (above) in reverse order...

The best advise I can give you, is to buy a Vesper Watchmate 650 display for your helm position....(and maybe even one for the Nav Station)...
Once you use it, you'll wonder why in the world everybody else's AIS displays aren't the same way!!!


Have a look at the Panbo article on the Vesper units....
http://www.panbo.com/archives/2013/06/vesper_marine_watchmate_still_the_leader_in_ais_co llision_avoidance.html


And, the Vesper pages...
http://www.vespermarine.com/


I could ramble on, but I think the above links and photos will give you most of the "AIS" answers...





3) As for MARPA, ARPA....
Yes, MARPA is "Mini-Automatic Radar Plotting Aid" and (as others have mentioned) is a Non-IMO compliant ARPA...

Not sure why the Zeus system isn't automatic, nor why it is limited to a few (max 10?) targets....
But again, that is system/platform specific....

As for the bemoan from some on the internet that "MARPA sucks", etc., here again, this is also system/platform specific (requiring decent software and system design) as well as requiring "fast heading sensors", etc.

Is AIS superior to MARPA for accuracy and conveying the CPA's, etc....
Yes, of course it is...
But of course, not everything floating, or surrounding us on the water, has an AIS transponder....so keeping a good watch, and use of radar (and MARPA as needed), will still be necessary for a long time to come!!!




4) To sum up...
I think most have the same reaction to having AIS on-board as you did...
It is a GREAT tool to have...

But, I think most (all) of your negative observations are Navico / Zeus issues, which are not present with my Raymarine system, nor with my Vesper Watchmate...




I hope this basic info and these brief comments, are helpful...



Fair winds..

John
s/v Annie Laurie

Well, the only fundamental problem I have with the AIS display on thee Zeus is that I can't see where we'll be at CPA. You summed it up perfectly -- a couple of cables astern of a fast ship is no problem; a couple of cables ahead is totally unacceptable. Plus, you don't know which way to turn, and you don't know between which ships you're going to pass when you go through a line of ships.

All I want is for my Zeus to display those blue dots like OpenCPA does -- that would nail the problem. I don't have room for another display at the helm and don't want to have to look at two displays at once in a tense situation.

Are you saying that your Raymarine display will show you changing bearings or relative positions at CPA? How?
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Old 08-06-2014, 13:06   #67
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Re: Thoughts about AIS

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Originally Posted by hoppy View Post

. . . .

With my Raymarine I could tell whether the CPA was in front or behind from the way the vectors were displayed.

. . .
I bet it's by using the COG extension lines, as described further up in the thread. This will kind of work IF the ends of your extension lines are somewhere near CPA. It will not work so well if the two vessels are moving at much different speeds, and CPA is not quite near the ends of the extension lines, although you can sometimes get a vague idea from looking at the relative positions of the two extension line ends.
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Old 08-06-2014, 13:25   #68
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Re: Thoughts about AIS

yes you can enable the vector on the raymarine AIS target, asnd the vector on your own vessel and it will show the interesction, but it won't show if you will arrive before or after the other vessel. Options to determine that are
1/ change course and see if the CPA increases or decreases
2/ place a waypoint and check the time to that waypoint, if its less than CPA the vessel will pass astern
3/ grab the binoculars or hand bearing compass and take a bearing
4/ step inside to the nav desk and check the OpenCPN AIS overlay

I usually do 1/, 3/ or 4/ in no specific order but OpenCPN is definitely the fastest and easiest to understand at a glance.
The best thing about OpenCPN is when crossing a busy shipping lane you can look and say to yourself, Ok Ill be crossing in front of that ship in 10 mins, behind the next in 15 and in front of the next in 20, it really makes it clear and Id suggest its the best on the market at the best price as well !
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Old 08-06-2014, 13:55   #69
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Re: Thoughts about AIS

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Originally Posted by monte View Post
yes you can enable the vector on the raymarine AIS target, asnd the vector on your own vessel and it will show the interesction, but it won't show if you will arrive before or after the other vessel. Options to determine that are
1/ change course and see if the CPA increases or decreases
2/ place a waypoint and check the time to that waypoint, if its less than CPA the vessel will pass astern
3/ grab the binoculars or hand bearing compass and take a bearing
4/ step inside to the nav desk and check the OpenCPN AIS overlay

I usually do 1/, 3/ or 4/ in no specific order but OpenCPN is definitely the fastest and easiest to understand at a glance.
The best thing about OpenCPN is when crossing a busy shipping lane you can look and say to yourself, Ok Ill be crossing in front of that ship in 10 mins, behind the next in 15 and in front of the next in 20, it really makes it clear and Id suggest its the best on the market at the best price as well !
Yes, well, the vector in the Raymarine is the same useless arrangement I have in my Zeus

Your checklist is interesting, especially number 3. So we have thousands of dollars worth of cutting edge marine electronics, and we're supposed to start writing down bearings from a HBC like we used to do?? Bullocks. The absurdity of this underlines the depth of the problem.

Ekh. Of those options I would go for 4, but really -- can't we have some decent information in the plotter display? How hard of a software update could that be? Navico, are you reading this thread???
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Old 09-06-2014, 08:13   #70
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Re: Thoughts about AIS

Why do some here say that the simple two line display is best? The OP operates in heavy traffic where full situational awareness must be quickly ascertained.

Click image for larger version

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This display provides the needed information.
  1. Your boat is the red one. The target boat is going at high speed in a traffic lane.
  2. You can quickly learn that the target is going to continue in the lane, and expect him to turn slightly to starboard to avoid the separation zone.
  3. Your boat is safely out of the traffic lane.
  4. Note that your heading is about 15 degrees to starboard of your projected track. This is due to current flowing starboard to port, and you need to be aware of it to avoid shallow water. The displayed soundings, and approaching land display allow making proper decisions.
This information is all the more necessary when running in fog. Quick situational awareness of your position, and AIS targets gives you more time to look for non-AIS boats on your radar.
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Old 09-06-2014, 10:05   #71
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Re: Thoughts about AIS

I use a Raymarine e7 chart-plotter on the outside helm but have installed a panel PC at the inside steering station. The PC runs SoftwareOnboard (SOB) by Digiboat. The AIS transponder is from Digital yacht and feeds both the PC and chart-plotter.

In the attachment - taken from the SOB manual - your own vessel (black circle and heavy black arrow) and the approaching vessel are both shown. The dashed guideline drawn on the screen shows the track of the target as it approaches the CPA. The brown double-ended arrow and two dots show the predicted positions and separation distance of the two vessels at CPA. These predictions are dynamic and constantly adjusting.

It makes it very easy to determine who will pass ahead of whom.

I use the e7 with its vector line when things are pretty obvious but the PC+SOB when things get a bit tense.

The second attachment is a real world screen shot taken as we crossed the English Channel in white-out fog. The fog came down about 5 miles out and we never saw anything until the breakwater at Cherbourg. I had installed the AIS the day before.

The detail isn't great but it gives the idea
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Old 11-06-2014, 00:32   #72
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Quote:
Originally Posted by bobsadler View Post
I use a Raymarine e7 chart-plotter on the outside helm but have installed a panel PC at the inside steering station. The PC runs SoftwareOnboard (SOB) by Digiboat. The AIS transponder is from Digital yacht and feeds both the PC and chart-plotter.

In the attachment - taken from the SOB manual - your own vessel (black circle and heavy black arrow) and the approaching vessel are both shown. The dashed guideline drawn on the screen shows the track of the target as it approaches the CPA. The brown double-ended arrow and two dots show the predicted positions and separation distance of the two vessels at CPA. These predictions are dynamic and constantly adjusting.

It makes it very easy to determine who will pass ahead of whom.

I use the e7 with its vector line when things are pretty obvious but the PC+SOB when things get a bit tense.

The second attachment is a real world screen shot taken as we crossed the English Channel in white-out fog. The fog came down about 5 miles out and we never saw anything until the breakwater at Cherbourg. I had installed the AIS the day before.

The detail isn't great but it gives the idea
Great stuff. So now we know three systems which show relative positions at CPA:

OpenCPN

Vesper

Software On Board


So it's not actually rocket science. I wonder why this is not implemented on plotters?
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Old 11-06-2014, 01:02   #73
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Re: Thoughts about AIS

I've installed an em-trak AIS on my boat, along with a furuno MFD12 chartplotter. This past weekend I had the opportunity to really use it as we were sailing across and along some heavily trafficed shipping lanes.

I'm not sure how your display handles this, but mine shows red arrows from my boats icon and also red arrows from the other boats (length of arrows determined by boat speed). If they cross, there is a potential situation. But it is relatively ieasy to see if they are crossing in front of you or behind, simply by the amount of the arrow on either side of the crossing arrows.

My system also shows (by small arrows) if the target is changing course.

Amazingly, I found that some of the larger ships actually made minor course adjustments and gave way for me when I crossed the lanes.

Will wonders never cease?

But I agree, AIS is indispensible when sailing in heavy traffic.
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Old 11-06-2014, 01:53   #74
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Re: Thoughts about AIS

Ais is fantastic as others have said. On my 40ft cruiser, we have a pc below running ocpn. At the helm is a 2nd screen off the pc vga port. We use AIS, radar, and all boat instruments via the pc, so all info, in exactly the same format is in both places. We use a Sony experia as a mouse and kb to drive the pc when in the cockpit. Works a treat, and is cheap and easy to upgrade. As you have seen above, open cpn does a great job with Ais. We have used this system for several years, open ocean and congested water. It's great.

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Old 11-06-2014, 02:06   #75
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Re: Thoughts about AIS

Quote:
Originally Posted by carstenb View Post
I've installed an em-trak AIS on my boat, along with a furuno MFD12 chartplotter. This past weekend I had the opportunity to really use it as we were sailing across and along some heavily trafficed shipping lanes.

I'm not sure how your display handles this, but mine shows red arrows from my boats icon and also red arrows from the other boats (length of arrows determined by boat speed). If they cross, there is a potential situation. But it is relatively ieasy to see if they are crossing in front of you or behind, simply by the amount of the arrow on either side of the crossing arrows.

My system also shows (by small arrows) if the target is changing course.

Amazingly, I found that some of the larger ships actually made minor course adjustments and gave way for me when I crossed the lanes.

Will wonders never cease?

But I agree, AIS is indispensible when sailing in heavy traffic.
Yes, my display also displays extended COG lines which show where the vessels will be in a given amount of time. This is somewhat dangerous because it is possible to set the time for other vessels and for your own boat differently, in which case you get a completely false idea of relative positions over time. If the times are set the same, then you see the relative positions at that time -- which is very useful in case that time is somewhere near the time of CPA.

Whether or not the lines cross tells you almost nothing.


Yes, AIS shows you what you could never see before -- when and how ships are changing course and speed. It's amazing how much you can see and know which was totally obscure before.
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