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Old 15-11-2011, 14:18   #16
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Re: AIS with Internet

One of my big questions until all of them it, that some yellow flashing one comes on a given area you are with light neither.
For me that most dangerous one...

May be watching,how the ship is in service when in a given month, may be looking for onto his name and his timetable. Onto PilotBook supplement perfect.
I talked myself into it: disappear a smaller one AIS, but the Internet one interests, what joins onto the Opencpn possibly.
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Old 15-11-2011, 15:15   #17
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Re: AIS with Internet

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Originally Posted by sinbad7 View Post
Gentlemen!

Whilst I must admit that the ability to follow ships voyages across the seas gives the much aligned 'armchair sailors' inmesurable pleasure,I do not think the intrepid sailor in action on the high seas should ignore ANY information contributing to his intelligent evaluation of his position and possible dangers.

Ignoring and refusing to evaluate AIS information received over internet is like refusing to accept weather prognosis because it may be inaccurate.

The navigator's conception of his situation relies on a great many factors which all contribute to give a position as accurate as the sum of information received.
A prudent navigator is constantly evaluating the information received.

Tore
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Originally Posted by sinbad7 View Post
goboatingnow

Of course an on board AIS receiver is more accurate in the immediate vicinity of your boat,BUT, it has a very limited range,and is unable to see ANY oncoming traffic beyond that range. Nor can it check for the whereabouts of any ship outside your own limited range. What if you would like to call a ship outside your range if you could not see it's name or callsign? Again,please read carefully my arguments in # 12

I agree with Dave that internet derived AIS information should not be an integral part of OCPN but can be accessed using the Route Manager's 'Additional information' box with links to several internet based AIS networks without having to leave your OCPN map.

Tore

AIS uses VHF frequencies in the same range as the marine VHF frequencies.

Therefore, theoretically, the AIS range is the same as your VHF radio.

So, how are you going to call this ship that is out of AIS range, and is therefore out of VHF range?

As to your arguments in #12:

If I have internet and want to see the internet data, I can bring it up on a web page. But I DON'T want outdated data cluttering up my live navigation screen and confusing me as to what is live and what was 5-15 minutes ago.

A prudent navigator uses everything available to him. But a prudent navigator also knows when to throw away something that is potentially more harm than good. I don't want to have to go through an education session anytime someone other than myself looks at my navigation screen, to explain to an experienced navigator why I thought it was a good idea to display on my screen where out-of-range boats were 15 minutes ago.

-dan
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Old 15-11-2011, 16:59   #18
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Re: AIS with Internet

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Originally Posted by bzs View Post
One of my big questions until all of them it, that some yellow flashing one comes on a given area you are with light neither.
For me that most dangerous one...
May be watching,how the ship is in service when in a given month, may be looking for onto his name and his timetable. Onto PilotBook supplement perfect.
I talked myself into it: disappear a smaller one AIS,
but the Internet one interests, what joins onto the Opencpn possibly.
Yes,those (yellow flashing ...where you are)are bad!Fishboats,Pilot Boats,fast boats-I hate em all at night when I can't tell what they'll do next!
You "talked yourself into it?" You bought an AIS?


..."joins onto the Opencpn possibly"
like Nohal's "Google Earth plugin" !...maybe it can be modified to include an AIS site when that is "on" in GE......when the box is checked,I mean...here's a picture that shows what I mean...

Click image for larger version

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Size:	378.2 KB
ID:	33723
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Old 15-11-2011, 19:47   #19
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Re: AIS with Internet

I can see in reading all these response that there is quiet a spread in opinion.

In our area, the waterway traffic is very complex, ferries vary there routes and speeds, tugs and tows move in just about any direction. The big ships can move really fast.

I can give you plenty of examples where the Internet info along with listening in on local traffic control provided the necessary help determine if a situation was a potential constant bearing decreasing range.

Thanks for listening, I did enjoys you posting.

Steve
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Old 15-11-2011, 19:50   #20
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Re: AIS with Internet

AIS is all about short range positional awareness. It takes the position, speed and course of transmitting boats in the viscinity. The age of that information is known and displayed for each vessel.

The position can be displayed as an overlay on a chartplotter and the currrent speed and course is stated and then extrapolated to determine the CPA and TCPA with regard to your own vessel.

When using an internet site, this information is not available; You do not have an indication of the age of the AIS transmission for each ship . You can't therefore establish a reasonably accurate present position. For the same reason, course and speed information may also be invalid. Accurate positions in short range situations are vital.

You do not have CPA and TCPA information at all. This is very important information. It tells you what the situation between you and any other vessel will be in the future, given that no course of speed changes are taken by either vessel. It is a primary source of information when determining course change requirements.

What you can establish from the internet is the fixed information that has been entered in to the AIS information fields; name of vessel, call sign etc.

Internet based displays of AIS information do therefore have a very limited use for navigation (call sign etc), but there is such a huge risk of misunderstanding what is being displayed (outdated information of uknown vintage) and it can be very misleading to those that don't fully grasp the implication of this (false positions of unknown accuracy).
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Old 15-11-2011, 20:17   #21
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Re: AIS with Internet

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Originally Posted by bewitched View Post
AIS is all about short range positional awareness. It takes the position, speed and course of transmitting boats in the viscinity. The age of that information is known and displayed for each vessel.

The position can be displayed as an overlay on a chartplotter and the currrent speed and course is stated and then extrapolated to determine the CPA and TCPA with regard to your own vessel.

When using an internet site, this information is not available; You do not have an indication of the age of the AIS transmission for each ship . You can't therefore establish a reasonably accurate present position. For the same reason, course and speed information may also be invalid. Accurate positions in short range situations are vital.

You do not have CPA and TCPA information at all. This is very important information. It tells you what the situation between you and any other vessel will be in the future, given that no course of speed changes are taken by either vessel. It is a primary source of information when determining course change requirements.

What you can establish from the internet is the fixed information that has been entered in to the AIS information fields; name of vessel, call sign etc.

Internet based displays of AIS information do therefore have a very limited use for navigation (call sign etc), but there is such a huge risk of misunderstanding what is being displayed (outdated information of uknown vintage) and it can be very misleading to those that don't fully grasp the implication of this (false positions of unknown accuracy).
Bingo! You nailed it. (bold emphasis above is mine).
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Old 15-11-2011, 21:05   #22
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Re: AIS with Internet

In some respects, this depends where you are. Stand alone AIS receive only systems are around $400 here. Not cheap. A dedicated receiver (circa $200) attached to a computer will let you display local AIS transponder data. Shipplotter, OpenCPN or other solutions are useful, though around Australia, you are limited to a 'radar' type display as there are very few free charts that they can use and none at all for the South Coast of Australia where I live. AIS B transponders are around $1500+ so not in my budget right now, if I have that sort of money, I'll buy a new radar instead (secondhand radar in Oz is like rocking horse manure for some unfathomable reason - if you are in Oz and have a used radar for sale at a reasonable price I'd love to hear from you.)

I've used a base station system to feed the Greek shipping site and I can say with reasonable confidence that the information I send to the site is shown in close to real time. I updated them every ten minutes or so and the data was shown within seconds of that. The situation in heavily trafficed areas (this isn't, there would be less than 6 ships in 'view' locally at any time most days, sometimes none at all.) may be different, I can't say, but I can say it would be useful for navigation, at least around here. This assumes you have internet connectivity, in Oz, that's up to about 50 miles from the coast, but there is a lot of coast and there are definitely gaps in the coverage. My current setup is an old scanner fed to Shipplotter. It works and I can tie in to their network if I choose, but it largely doesn't matter, I will be using it in 'radar screen' mode mostly, it can download OpenStreetMaps for any area, but they are not nautical charts by any stretch, still they do show relative positions quite well. I have Garmin Bluecharts and NRoute, but no way to force either to display AIS targets and of course neither Shipplotter nor any other non Garmin software that does display AIS can use the Bluecharts. There is no equivalent to the free NOAA stuff in the US. They do have a few (very old, weird datums) Australian charts, but only for the north, west and east coasts and not anything like recent even for there.

You use what you have. Where you are and the depth of your pocket will affect what you have. I've love an AIS B system and a chartplotter that can display the AIS data live on it, but it would cost roughly half what my boat did...

AussieGeoff
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Old 16-11-2011, 03:10   #23
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Re: AIS with Internet

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Originally Posted by AussieGeoff View Post
AIS B transponders are around $1500+
....
They do have a few (very old, weird datums) Australian charts, but only for the north, west and east coasts and not anything like recent even for there

AussieGeoff
There are now transceivers for 500US$ or 400 around (Em-trak B-100 - there is a Raymarine near relative of that one as well). Should been available at down-under as well.

With respect to the charts we would like to hear your opinion about the NGA charts you will find at NGA Charts Status at OpenCPN.info (English)
Australia is within Region7. You will have to register, download the chart you are interested in by right-clicking and "save to".

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Old 16-11-2011, 07:28   #24
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Re: AIS with Internet

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There are now transceivers for 500US$ or 400 around (Em-trak B-100 - there is a Raymarine near relative of that one as well). Should been available at down-under as well.
I've not seen them anywhere here, or even on the net, but I'll look into that, thank you.

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With respect to the charts we would like to hear your opinion about the NGA charts you will find at NGA Charts Status at OpenCPN.info (English)

Australia is within Region7. You will have to register, download the chart you are interested in by right-clicking and "save to".
I've been following that forum thread and have looked at them. First let me say the guys involved in this project are doing a wonderful job, it'd tricky and tedious. But the stuff they have to work with from around here is pretty much obsolete crap.
The ones they have gotten to a usable state so far are simply datum corrected (well sort of) versions of some old (I think RN and/or RAN) black and white charts. As far as I can tell, I've yet to find any that cover the south coast west of about Melbourne and east of the Bight. I live in South Australia on Spencer Gulf and unless I have missed it somewhere, there are no free charts anywhere for this area, roughly the centre of the south coast, west to Melbourne. .
Some of the charts of the East coast, west coast and north coast aren't bad and are probably useable with care.

I note that several charts (including one for part of my area) are on the NOAA site but apparently can't be corrected because the datum is either something truly weird and/or it's a weird projection and the project workers weren't able to do anything useful with it.

The Australian Hydrographic Office are the official source for charts here and presumably Garmin et al license their Aussie chart data from them. It is NOT freely available even to the taxpaying public, which is pretty poor form really, considering the taxpayers payed for the blasted things. and the license fees are ridiculous. Literally thousands. You can buy them in electronic form, but only in some oddball proprietary form that they won't license, so you can only read them with their proprietary reader, which means they are useless for OpenCPN or any other chartplotter basically unless someone reverse engineers the format and comes up with a plug in for OpenCPN, which is probably unlawful.

This makes using OpenCPN somewhat problematic in Australian waters as there are only partial charts.

The US sailors are badly spoiled, the NOAA charts are generally good and freely available and kept at least somewhat updated, the selection of Aussie charts on the NOAA servers (where the OpenCPN mob got the onese they are working on) are from at least the sixties and it's by no means a full set, particularly along the south coast.
Presumably this is because the approaches are from the west, north or east, not the south (well, penguins maybe come from that direction).

If you know of anything for this area, I'd love to hear about it.

AussieGeoff
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Old 16-11-2011, 08:02   #25
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Re: AIS with Internet

AussieGeoff,lots of good points!
your AIS participation is much appreciated!.

per charts:I don't know why the Australians would object to a plug-in made for OpenCPN- it'd be more charts sold!There's already one available for Canada's charts.
The NGA charts project...indeed the Oz coverage is pretty slight and they're pretty much an historical project as they are now because,to begin,the first step has been to calibrate em with only the data available on the chart image.For what it's worth,now that the grid is in place,these can be shifted to WGS84 in another edition.

as has been hinted,I don't think anyone is going to enter a Traffic Management System relying on an internet connection to an AIS site.Not yet,anyways.The future may hold something altogether different.Satellite /upload/download to Realtime Google earth (that includes soundings,racons,instant texting,and so on).Whatever electronic doofunnies people are shelling-out for now,I'm secure in my belief that 5 -7 years from now ,it'll all be junk.....
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Old 16-11-2011, 08:07   #26
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Re: AIS with Internet

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Originally Posted by sgschwend View Post
I can see in reading all these response that there is quiet a spread in opinion.

In our area, the waterway traffic is very complex, ferries vary there routes and speeds, tugs and tows move in just about any direction. The big ships can move really fast.

I can give you plenty of examples where the Internet info along with listening in on local traffic control provided the necessary help determine if a situation was a potential constant bearing decreasing range.

Thanks for listening, I did enjoys you posting.

Steve
Yes,here too,it seems very useful....If anyone knows how I can get my ol cellphone to see these AIS sites on Opera's mini-browser,speak up!
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Old 16-11-2011, 08:22   #27
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Re: AIS with Internet

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Originally Posted by HappySeagull View Post
AussieGeoff,lots of good points!
your AIS participation is much appreciated!.
Pleased to be of help, I hope I can be more.

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per charts:I don't know why the Australians would object to a plug-in made for OpenCPN- it'd be more charts sold!There's already one available for Canada's charts.
Usual reasons. They make a lot of money from it and don't want to share.

That's why the charts in electronic form are in some convoluted proprietary format that they won't license. If someone worked around it by rev engineering, they might well scream that their copyright is being infringed by using other than their proprietary stand alone chart reader. The govt makes the laws and we don't even have the benefit of constitutional protection for pretty much anything Americans take for granted. Free speech for instance. You CAN be arrested for what you say, or write and in some cases, even for what you read.
If you think I don't trust the sods to do the right thing, you'd be right.

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The NGA charts project...indeed the Oz coverage is pretty slight and they're pretty much an historical project as they are now because,to begin,the first step has been to calibrate em with only the data available on the chart image.For what it's worth,now that the grid is in place,these can be shifted to WGS84 in another edition.
Yes, that seems to be Phase 2, that may eventually produce some more usable material in time. It's a good project and will doubtless produce long term benefits.

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as you pointed out,I don't think anyone is going to enter a Traffic Management System relying on an internet connection to an AIS site.Not yet,anyways.
No. Not around here. Largely because I don't believe even one exists in all of Oz.

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Originally Posted by HappySeagull View Post
The future may hold something altogether different.Satellite /upload/download to Realtime Google earth (that includes soundings,racons,instant texting,and so on).Whatever electronic doofunnies people are shelling-out for now,I'm secure in my belief that 5 -7 years from now ,it'll all be junk.....
Having worked in IT for many years, I have no doubt you are correct. I've worked with systems we got literally for nothing, that cost literally millions less than ten years before. Wonderful engineering and virtually bombproof, but think big refridgerator and that didn't include the disk drives, some of which were mains powered! Sadly it's razor blades now.

I did in fact find the AIS B transponder that was mentioned, for around $540AU, which is about a grand less than the cheapest one I'd seen previously. Having seen what goes into these things, there is no doubt they are ridiculously overpriced and I've no doubt they will start to come down or some bright spark will figure out a way to do it with a computer and a sound card interface, if it hasn't been done already. You can certainly do that for receive, TX can't be that hard, the protocol is well documented and the 9600bps modulation is easy for a sound card in even a five year old computer.

Shipplotter handles the whole AIS rx only thing quite reliably, I use an old scanner with a discriminator tap. Works like a charm.

Consider PACTOR modems, the price of them is nothing but highway robbery because of the extortionate license fees for the protocol per modem. Ned Kelly would have loved them.
I will be using WINMOR, which is free and needs only a sound card and interface to the HF radio, PACTOR may have slightly better performance, but not thousands of dollars worth.

I'll be watching the map project with interest.

AussieGeoff
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Old 16-11-2011, 09:02   #28
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Re: AIS with Internet

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I've used a base station system to feed the Greek shipping site and I can say with reasonable confidence that the information I send to the site is shown in close to real time. I updated them every ten minutes or so and the data was shown within seconds of that.
In those 10 minutes a container ship at cruising speed has travelled about 5 miles.
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Old 16-11-2011, 09:17   #29
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Re: AIS with Internet

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In those 10 minutes a container ship at cruising speed has travelled about 5 miles.
You have container ships out there travelling at 25 knots ?
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Old 16-11-2011, 09:18   #30
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Re: AIS with Internet

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In those 10 minutes a container ship at cruising speed has travelled about 5 miles.
Hmm, cargo ships around here seem to cruise around the 14 knot mark, on that basis, 10 minutes is closer to 2.5 miles.

But that's okay, the dry land I'm on wasn't moving at all (well, maybe a few millimetres a year)

If I was using it for a collision avoidance assistance (there is NO substitute for a good all round lookout, day, night or in between) I'd refresh it at not more than sixty second intervals, so a cargo ship at 14kts will have moved around a 1/4 of a mile. Even allowing another thirty seconds for lag and a redraw, that's still well under a mile it will have moved. If you are opposite direction traffic, the rate of closure will of course be the sum of your speeds, or some vector of that depending on the angle. In either case, sixty seconds should be adequate provided the traffic is identified some miles away, preferably beyond visual range. The more lead time you have, the smaller the course correction needed to avoid a collision or even a close encounter.

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