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sinbad7 29-09-2009 05:28

Re my #60
What happens when MANY boats start to combine their GPS/AIS messages for upload to the AIS networks? Will we see several red boat icons displayed on our maps? Don't really understand WHY anybody would want to combine the two sentences. Having established a GPS position,it is passed on to the navigation system which will transmit it's total information to the network and local surroundings. Combining the GPS sentence AGAIN seems confusing and superfluous. Would it not be possible to EXCLUDE the GPS sentences from the AIS datastream?

idpnd 29-09-2009 05:52

AIS hub, answering an older question of mine, provides the typical "add a feed, get global data back" sharing system, plus aisdispatcher - AIS NMEA data forwarding utility for linux. :thumb:

blubaju 29-09-2009 20:22

Quote:

Originally Posted by sinbad7 (Post 338929)
Re my #60
What happens when MANY boats start to combine their GPS/AIS messages for upload to the AIS networks? Will we see several red boat icons displayed on our maps? Don't really understand WHY anybody would want to combine the two sentences. Having established a GPS position,it is passed on to the navigation system which will transmit it's total information to the network and local surroundings. Combining the GPS sentence AGAIN seems confusing and superfluous. Would it not be possible to EXCLUDE the GPS sentences from the AIS datastream?

in my understanding NMEA was developed 30 years ago for use on boats in a closed environment, not for sending the sentences all around the world. On my boat I want the NMEA stream to contain all relevant data. Anyway NMEA 0183 is considered obsolete nowadays, we are in a transition period to NMEA2000, a CAN-bus derivate. Yes, I do know about the advantages and limits of NMEA0183 -

Your problem is, some do not filter the stream going to Siitech, but Siitech could be bright enough to filter the incoming sentences, if they do not do it, you could still filter them on your side.

AIS in my understanding was developed as an onbord support for collision avoidance and not for armchair sailors delightening themself on the ship traffic on the other end of the world. Maybe those should find their own solution for their hobby.

Christian Van H 29-09-2009 20:32

AIS. AIS. AIS. AIS. AIS. AIS. There, just in case you haven't already read it enough. Does anyone here actually navigate with this wonderful navigation program?

blubaju 29-09-2009 22:33

Quote:

Originally Posted by Christian Van H (Post 339420)
AIS. AIS. AIS. AIS. AIS. AIS. There, just in case you haven't already read it enough. Does anyone here actually navigate with this wonderful navigation program?

openCPN?
under evaluation until it outperforms MaxSea ;-)
every 20 or so minutes it just disapears, so I can not use it

and yes, you are right

sinbad7 30-09-2009 05:23

I think someone got out of the wrong side of the bunk today. :banghead:

Personally I think AIS is the most significant development for safety at sea since the compass.. but then again there are those that are hauled kicking and screaming into the twenty-first century....:whistling:

SAILORS within 3G reach are starting to use available private AIS networks as a 'virtual AIS transponder' expanding their normal observation range considerably. They are not interfering with anyone else but users of the private network they are feeding into. The same is the case for those with dedicated AIS receivers/transponders on board.

Siitech's normal Web VTS browser does not display these extra GPS sentences, but then again it is NOT a navigations program.

Having access to large networks (6000 vessels) I am testing out the various facets of using AIS with OpenCPN and hope it will not be too boring for some.

Having spent most of my life at sea as a navigator,YES ,I am now an armchair sailor, but hope I have something to contribute to this forum.

LeaseOnLife 30-09-2009 07:27

Thanks to sindbad, testing opencpn with a large number of targets is a good thing.

But may I ask to mention sxxtech less often. They are a commercial venture, and yes, I understand they have some freebies to lure people into buying. Mentioning the name just all too often sounds like advertising.

For comparison of AIS displays I wouldn't mind screenshots (opencpn vs xxx) without having to go the the sxxtech website.

To support sinbad: I do think it is a bug if opencpn moves the ownship if GPS NMEA source is none (by using the RMC sentence embedded in the AIS data). But it is a bug which is irrelevant for people using a real AIS on a boat. It's up Dave if he wants to acknowledge this as a bug with enough priority and fix it.

sinbad7 30-09-2009 08:48

If AIS is of so little importance or interest in this forum I will certainly not waste my time elaborating any further. Siitech should not be of any offense to the users of OpenCPN as their browser and network is for FREE use and is NOT a competing navigation program but a VTS traffic surveillance utility. Whether or not this constitutes an effort to 'lure' people into buying a port surveillance program will have to be up to the individual user. Personally I am very grateful for the free services they offer.

Christian Van H 30-09-2009 16:23

Quote:

Originally Posted by sinbad7 (Post 339514)
I think someone got out of the wrong side of the bunk today. :banghead:

Personally I think AIS is the most significant development for safety at sea since the compass.. but then again there are those that are hauled kicking and screaming into the twenty-first century....:whistling:

You are more than entitled to your opinion Sinbad, but I find it very hard to believe anyone who's ever sailed a boat can put AIS before GPS as the most significant development since the compass. You dont need to haul me anywhere, and unless you are blind, you still dont NEED AIS to sail a boat anywhere in the world...IMHO

sinbad7 30-09-2009 17:04

As anyone knows,GPS and other nav instrument data is an essential part of the information sent by the AIS transponder to vessels within range. GPS alone does not transmit your boats location to other ships.

Of course it is possible to do without AIS,the vikings found America with a magnetic stone in a string,but we like a little more security and comfort in our boats today. But,as the saying goes:'Some like the daughter,some like the bowlegged mother'.
It's called freedom of the seas!!

Christian Van H 30-09-2009 17:35

Quote:

Originally Posted by sinbad7 (Post 339888)
Of course it is possible to do without AIS,the vikings found America with a magnetic stone in a string,

If I keep spending too much on this refit, I might only be able to afford a magnetic stone on a string! :D

blubaju 01-10-2009 04:10

WHY anybody would want to combine GPS & AIS
 
Quote:

Originally Posted by sinbad7 (Post 339888)
As anyone knows,GPS .... is an essential part of the information sent by the AIS transponder to vessels within range.

but this is exactly what you complain about when you receive it:

29-09-2009 03:49
I am receiving NMEA messages which are a mix of AIS and GPS sentences:...

29-09-2009 20:28

Don't really understand WHY anybody would want to combine the two sentences.

Once you tried openCPN on a real boat you will understand it, AIS comes in and ships data comes in, maybe some people have a RADAR too, that unit could use combined GPS and AIS. Now why should I separate that again if even my openCPN (and all other software) has no problem with it.

I do not think many will spend money or time for that, I did it as it is part of my software multiplexer, but what AIS-dispatcher allows and what not is beyond my investigation, I did not use it.

It is the receiving site to filter what is unwanted, openCPN is not transmitting anything - Autopilot set aside.

And please be carefull, to much headbanging might cause serious injury:flowers:

sinbad7 01-10-2009 05:09

I think perhaps you are confusing the issue somewhat. A normal AIS message does NOT contain separate messages from ANY on board equipment,including the GPS,but assimilates all the info in ONE message,thereby making duplicate messages superfluous.

People are however experimenting with the transmission of AIS or GPS messages over 3G and other telephone networks,feeding their data to private AIS networks for FREE display on any internet connected PC. This is not creating any disturbance to normal on board operation of the AIS receiver/transponder. Should vessels within the range of your AIS receiver/transponder start sending out separate GPS/AIS messages,confusion could arise with duplicate 'MY ship' icons being displayed in OpenCPN and even changing the location of your map. If you read my previous messages on the subject,it already happened to me on several occasions in a similar way.

I would have thought it would be easy to create a filter in OpenCPN to avoid incoming GPS position messages contained in the AIS data stream, but Dave does not like the idea as it might interrupt reception of other GPS transmitted data such as routes and waypoints. I am all for technological advances as long as it does not disturb or interrupt other peoples data.

blubaju 01-10-2009 06:10

confusing AIS
 
I think perhaps you are confusing the issue somewhat.
Perhaps

A normal AIS message does NOT contain
separate messages from ANY on board equipment,including the GPS,

this is confirm with my knowledge so far, though I did not see the data stream of an AIS transponder with built-in GPS yet - but they exist!

but assimilates all the info in ONE message,

disturbances rising

thereby making duplicate messages superfluous.

total confusion

People are however experimenting with the transmission of AIS or GPS messages over 3G and other telephone networks,feeding their data to private AIS networks for FREE display on any internet connected PC.

I can follow again

This is not creating any disturbance to normal on board operation of the AIS receiver/transponder.

Comprehende

Should vessels within the range of your AIS receiver/transponder start sending out separate GPS/AIS messages,confusion could arise with duplicate 'MY ship' icons being displayed in OpenCPN and even changing the location of your map.
Non comprehende, why should I import the data stream of another vessel into my onboard system when I am sailing?

If you read my previous messages on the subject,it already happened to me on several occasions in a similar way.

Yes, I know, I read all of them regarding openCPN

I would have thought it would be easy to create a filter in OpenCPN to avoid incoming GPS position messages contained in the AIS data stream, but Dave does not like the idea as it might interrupt reception of other GPS transmitted data such as routes and waypoints. I am all for technological advances as long as it does not disturb or interrupt other peoples data.

That request is not easy to solve, how should openCPN determine which $RMC comes from the own ship or another? And there is not only RMC. The only solution - and this is still far from perfect - dead reckoning done by openCPN, after an initial position acknowledgement from the skipper. openCPN then would make permanent plausibility checks if the position COULD be valid. If the sender is to close, bad luck.

I think it is the ship (or station) owners responsibility to keep his NMEA data stream clean of any incoming wrong messages and only mux what has to be muxed. How would the autopilot know which RMC is the correct one? But perhaps I am muxed and still did not get it.....

Hope Christian went for a BIG cup Pitta tea meanwhile and did some maintenance on his boat :whistling:

idpnd 01-10-2009 07:11

capcode is a related free software project seeking to implement VMG from NMEA data, polars, routing etc.; perhaps cooperation is possible?


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