[ReeferJon]

I've just received an email from Rich at GPSNavX confirming that their software works with the Nasa AIS receiver (although there are a few minor issues.)

Begin forwarded message:

> From: Tom MacNeil <tamacn@earthlink.net>
> Date: April 20, 2005 6:05:35 AM PDT
> To: Ray Rich <gpsnavx@mac.com>
> Subject: AIS Receiver Testing
>
> Hi Rich,
> Spent 4 days testing out the NASA AIS Receiver.
>
> For the most part I think it worked pretty well. The only problem I
> can find is missing names and calls. You had mentioned something about
> this before. This seem to be a problem, perhaps you may have a
> solution... (after talking to you I understand names are transmitted
> once every 20 min. Can we hold onto them for three cycles before
> graying them out?)
>
> The NASA receiver also puts out an extra sentence. The AIS window
> shows a yellow circle (along with the green) and I assume that is info
> that GPSNavX can't use. Since GPSNavX users will probably purchase
> this receiver in greater numbers, would it be worth looking into what
> this sentence provides?
>
> I loaded the program they sent along with it using VPC. Here is the
> info the NASA is capable of delivering.
>
>
> It would be great if we could get all the data... destination (was
> accurate up here) width and draft and maybe MMSI for DSC.
> I was able to get incredible distances from the system. All the way
> from Port Angles to Howe Sound about 70 miles (I was in the middle
> with my antenna on top of a 55 ft mast).
> I received as many as 60 contacts in a session.
>
> When you start the receiver it acquires the contacts
> immediatly...Names can take as long as 20 min to fill in. The system
> seemed to have a much harder time with the names (probably only gets
> one shot at them)
>
> Here is a typical screen shot of cruising grounds in BC canada

[Guest]

http://www.navcen.uscg.gov/enav/ais/default.htm

[ginginsman]

Ben Ellison mentions getting two recent emails on the NASA AIS

http://www.panbo.com/

and I'll brag on having sent one of them

Can any one of you enlighten him about the frequency question? Would help keep the Mac navigation world profile up a little bit if he gets the info via MacSailing.Net!

[GPSNavX]

Can receive one channel at a time, by default it is set up to receive channel A.

One can programtically select channel B by sending this NMEA command..

$PNMLC,c*hh<CR><LF>
Where:
c is the channel receive mode as follows:
A = Channel A (channel 1)
B = Channel B (channel 2)
hh = Checksum as defined in NMEA 0183
<CR><LF> = Carriage Return, Line Feed sequence as defined in NMEA 0183

[cyberhusky]

Is it possible to have boats shown with their correct scale when using AIS with GPSNavX? Like PC Maritime's Navmaster Superyacht AIS package does! This way one can better realize of what's coming along :-)
For more info check http://www.panbo.com/yae/archives/000998.html .

A screenshot can be seen here http://www.panbo.com/yae/archives/Pont%2...00dpi.html

[GPSNavX]

The problem with most Nav apps is all the screen realestate they waste. The example screen shot you linked is a perfect example of that. Look at all that "dead" area that could be used by the chart - the most important thing.

Scaling the AIS targets to actual size only makes sense when the zoom is at 100%. Imagine if zoom is 25%, the targets would be so small on a large scale chart.

GPSNavX does draw AIS targets that are less than 200' at 1/2 size as normal targets. Also keep in mind many targets do not provide length info. Why does one care what the MMSI is?

[ReeferJon]

GPSNavX does draw AIS targets that are less than 200' at 1/2 size as normal targets. Also keep in mind many targets do not provide length info. Why does one care what the MMSI is?

You need the MMSI number so that you can DSC VHF radio the vessel if you're in a potential collision situation...

[cyberhusky]

You need the MMSI number so that you can DSC VHF radio the vessel if you're in a potential collision situation...

I think the AIS info shown in an extra window, which one could always close, shows important infos. The MMSI number is a must to have. As from 2005 on all boats going offshore must haavd DSC VHF.

OTOH as GpsNavX stated here a further info window leaves less place for navigational chart window. But IMHO AIS like Radar Infos are important to have as they can secure one from collisions! then a further info window is more important than more place on the navigational chart window, especially as one needs to react fast enough to avoid collision.
I wished we would have had AIS on our sailing boat 1-2 weeks ago. We only escaped a collision by the last second!
The boat (Netherland Plattbodenboot) going under engine, nearly crunched our boat under sail! Though they did saw us, they didn't change their course, so we had to turn in the last second. Later the other boat excused themself. With AIS I would have seen the near-upcoming collision earlier as I was in front of my iBook check the course to go.

[GPSNavX]

You need the MMSI number so that you can DSC VHF radio the vessel if you're in a potential collision situation...

Have any of you actually entered a MMSI number into your radios and communicated wtih the vessel? I believe most communication is still originated with vessel name or call sign.

I doubt many will go to the trouble to connect their VHF radios to their Mac's (Yet another USB port needed) even if there is a NMEA command to contact via a MMSI number.

[ReeferJon]

Just read a post on another site. Apparently there are two NMEA sentences called DSC and DSCE that are for streaming data from some DSCVHF radios. http://www.boating-forum.com/electronics...47249.html

Apparently these sentences will give you the location of a received DSC radio call (such as a MayDay call) and the MMSI number of the vessel calling.

Potentially, this means that you could flash up a "Incoming call from 'Reefer'" and flash the vessel's location (or AIS marker) on screen.

Now I wonder if it works the other way round (IE.. click on an AIS marker on screen, and then DSC VHF call that specific boat...)?!?

[GPSNavX]

Seems like this DSC NMEA stuff is still be sorted out. It will be a while before there is much connectivity between VHF radios and Nav software. It's not that it is difficult to support such functionality in a nav app. The difficulty is with getting the NMEA data to the Mac. Easy enough to plug in a GPS receiver or AIS receiver, but now add instruments, autopilot, VHF radio, etc and you have allot of connections. Sure you can use a NMEA multiplexor, but from what I have seen they are not up to par yet with this new ITU data NMEA sentences.

I am happy to add more NMEA capability to GPSNavX, but I need it spelled out specifically in a specification and I need to the ability to test a configuration. In otherwords the solution needs to be universal in that it will work with all DSC VHF radios.

[ginginsman]

You need the MMSI number so that you can DSC VHF radio the vessel if you're in a potential collision situation...

Have any of you actually entered a MMSI number into your radios and communicated wtih the vessel? I believe most communication is still originated with vessel name or call sign.

I doubt many will go to the trouble to connect their VHF radios to their Mac's (Yet another USB port needed) even if there is a NMEA command to contact via a MMSI number.

Interesting account of a yacht using the MMSI feature here. These are not situations we'll all be in, but having been through the Straits of Gibraltar at night in 1984 (before all this lovely gadgetry), tacking up the separation zone between the ship channels, I would love to have had an AIS:

http://www.motorboating.com/motorboat/el...19,00.html

[JackConnick]

I thought I read it here somewhere, but what is actually needed to install a NASA system on a small sailboat?

I have serial mini-din wiring from my Garmin up to my laptop station, looks like all I need is to add in the NASA receiver with the GPS wire, add power and pass up to the iBook. But what about an antenna? Can I duplex my VHF antenna? What are some install ideas? What cables do I need?

I think this has great value as I don't have radar.

Jack

[GPSNavX]

scroll down to "Adding AIS"

http://www.gpsnavx.com/html/navsolution.html

Best not to share the VHF antenna. AIS comes into GPSNavX typiically through a second port via a Keyspan adapter. keyspan also makes a 4 port model if you only want to tie up one USB port.

Lastly do not run the GPS through the AIS receiver as it filters out all but one GPS NMEA message.