Tag Archives: AIS

AIS Now Being Served In The Cockpit (sans wires)



That’s my Droid sitting there with the same image as the laptop. Well actually that’s not just an image, it is the laptop streaming content to my Droid and vice versa. We now have the ability to see and control our AIS information (and other info such as XM Weather, GPS diagnostics, etc.) from the laptop in the Nav Station with any Android device anywhere within range of our on-board router — about three boat lengths. I now have a good reason to buy an Android tablet — screen size. This arrangement is much less complicated than our original arrangement.

All that was required was the Splashtop Personal app on the Droid and a streaming application on the laptop. Since these devices are on the same wirelesss network (logged in on the same router) the service is free. And if you wanted to do this from a separate network, from anywhere, it’s cheap. Splashtop can service Google Android Devices, iPad, iPhone/iPod, Mac, Windows, Win 8/RT & WinPhone.

If I discover any problems, I’ll post them here, but with 15 million users, this is not a junkyard app.

NMEA Pro Omnibus — $15U.S.

We have all our navigation equipment at the pedestal except for AIS (Vesper Marine)  and XM Satellite Weather. Both devices output data via USB. For about $300 we might be able to port the AIS data directly to our pedestal via our Ethernet backbone. However, we’d need an additional $500+ display as the chartplotter is nine years old, and is set up for MARPA. AIS was not broadly available then. There is no room at the pedestal for another display even if we could get the data there.

AIS Display


Another $300 might be required to multiplex this AIS NMEA 0183 data stream at 38400 baud with the NMEA 0183* data that already flows on the Ethernet backbone at 4800 baud. This might or might not work (The multiplexer device tech data says yes, users have told me sometimes.).

The XM data format is proprietary, and next I’ll be trying to figure out how to port it to multiple devices. It isn’t essential to do so since it is a long baseline planning tool — except when doppler radar loops are involved.

We were disinclined to spend ~$600 on a maybe solution.

As a result of our need, then desire, to stay connected, we have second backbone. It is wireless. We have a boosted antenna on the davits connected to a USB-powered router below — any wireless enabled device on the boat, laptop. reader, smartphone (cellular off) can connect from anywhere. So the challenge became to move the AIS data/information to the cockpit at low cost.

Wireless AISStep one was to move the USB delivered NMEA data to the wireless backbone (using TCP/IP). This requires a server — it’s what servers do. We already had one. It is part of the Rose Point Coastal Explorer software. But this software is a memory hog on the 12 year old IBM X-40 I use in the nav station. I didn’t want to have it running because it interferes with the weather software smoothly updating. So I found GPS Software for Google Earth — by Greg Heppenstall. $15 via PayPal later and I had a smoothly functioning server on the X-40 and a similar client on the environmentally protected laptop in the cockpit.**

Because I also use a piece of navigation software that can only accept NMEA 0183 via a COM port, we needed to find a software solution for binding a virtual comm port on the cockpit laptop to the wireless backbone. I found the HW-VSP3 software (free for single port, personal use).  While this must be reset each time it is used, it takes seconds, and free is a good price for something tested in a demanding market.



So now all our AIS data/information and anchor watch data is available anywhere on the boat*** as long as the router is functioning. So it’s time for a spare router ($19 when we bought the first one, now $27. Still a bargain).

Total tab with spare router = $42. Much better than $600.

*Yes we know, NMEA 2000 has arrived. But it is expensive to retrofit, requires special cabling and connectors, and is aimed at a segment of the market that needs its feature set — we don’t, and a huge number of boats never will, and NMEA 0183 will hang around for decades.

** We are not fans of smartphones or tablets in sailboat cockpits. For those who navigate from environmentally protected spaces and who have the time and navigation space to squint at tiny screens with sun dilution, they may be useful. Having said that, when in network coverage, we have benefited from these devices (mostly doppler radar displays). We just have no interest in relying on them or making them the centerpiece of our situation awareness. If others want to use them, fine, as long as they don’t contribute to accidents.

***Even the TV, as it can be connected to the laptop via HDMI or S-Video, and we are looking at how to port low data rate imagery (weather and nav) to the TV via wireless. Also, since we have the boosted antenna on the boat, it may be possible to get the AIS/Anchor watch data to a portable device when we leave the boat.

Anchor Dynamics and Anchor Watches — Not There Yet

Among the Crowd

Among the Crowd

Even when we aren’t traveling, as long as we are afloat, we are moving. Whether it is surging in a slip (as we are now) or wandering around a mooring or anchor, which we prefer, we are moving. When it’s at anchor, we can be moving a lot.

The picture below shows how much. And remember this picture was among as many as 30 other anchored boats. Some of these were charter boats that snuggled in too close, dropped some amount of rode, and went to the beach. The worst of these swung within 8 feet of us a couple dozen times in one morning. Then the wind switched, and they came back absolutely clueless of the danger they had created for us and the trawler anchored on the opposite side.

real anchor watch1

The tracery of black dots is the sum of all our positions while anchored in Treasure Cay’s basin. Note these are the positions of the AIS GPS antenna, not our bow and not our anchor. For this experiment, we set the warning ring very large to capture the entire picture.

real anchor watch2The range and bearing provided is between the current GPS position and the one when we anchored–the lower black arrow. The upper black and blue arrows point to the GPS position we recorded when we dropped the anchor. The larger translucent circle [graphic addition encompassing 1.1 acres] bounds all our maximum (taut rode) distance from the anchor. The inner circle our minimum (slack rode) distance, except…

real anchor watch3When the strong pre and post frontal winds abated, we entered a two day period where the wind circled the compass. As this period began, the center of our swing circle transitioned and we were no longer swinging to our anchor.

real anchor watch4

The circle became much smaller and it spiraled (as in wound around something on the bottom) into a set of smaller taut-slack ellipses. How the swing circle returned to the larger one we can’t be sure as there are no time stamps with these positions.

So what did we learn?


  • 121 ft taut circle (84 ft of chain in a catenary curve and 37 feet to GPS antenna)
  • 97 ft slack circle (97-37=60 ft of chain wandering across the bottom when the wind dropped.)


  • 80 ft taut circle (43 ft of chain in a catenary curve and 37 feet to GPS antenna)
  • 74 ft slack circle (74-37=37 ft of chain wandering across the bottom when the wind dropped.)
  • Creates the appearance we are anchored on ~40 feet of chain.

Net taut chain reduction due to suspected chain wrap 84 ft-43 ft =41 feet. If this wrapped in perfect circle, the circle dia. would have been 13 ft +. If it was wrapped around a square block, the block would have been 10 ft+ square.

TreasureCayThe bottom here has abandoned concrete mooring blocks roughly 4×4 ft. We believe we wrapped two of these and that’s why they we have elliptical swing behavior — these accounted for roughly N-S major axis. People with more experience here have now told us to anchor along the channel edge to avoid these blocks.

And no anchor watch would have told us what was going on! The hand held Drag Alarm based on anchor drop position would not have seen this, the boat moved toward the anchor position, not away. The AIS Swing  Alarm would not have seen this, the swing was reduced not increased nor even shifted relative to the larger swing behavior.

Why is this a big deal? It happened on days when we went ashore because the weather improved. It gave arriving boats a false picture of how our boat would swing when things returned to normal. [This was not the case with the bare boat that nearly hit us. We were at full radius. They were more than clueless but less than competent.]

None of the technologies employed worked.  What is needed is the ability to define a space — a fence — of any shape desired and to do so without having to buy yet another piece of electronics. (see below) We can do this roughly with our chart plotter by saving waypoints with overlapping proximity warning circles, but it is crude, and the chartplotter takes too many amps.

A Fence (smartphone apps need not apply)

Mashup…what a word, what a word

You may be variably familiar with the term Mashup.  Wikipedia defines it thusly:

In Web development, a mashup is a Web page or application that uses and combines data, presentation or functionality from two or more sources to create new services. The term implies easy, Continue reading

One Antenna to Rule them All.2

As I noted on June 7th, I decided to switch the new amplified Splitter in parallel with the VHF, Stereo, and AIS. This way when any one of the three was switched on, the Splitter would be as well. The SP-160 would still be still fuse protected between the junction of the three red parallel wires and splitter. Well after I redid the  Continue reading

One Antenna to Rule them All

No, this is not some new Homeland Security Initiative.

I talked with Steven Gloor of Vesper Marine quite a bit before deciding on the Vesper Marine 850 last October. I wanted to stick with one masthead antenna. He counseled us to use their SP-160 powered (amplified) splitter as most of their testing indicated a standard splitter would deliver uneven performance if  Continue reading