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Interfacing an Autopilot During the winter of 2001 I installed a Simrad/Roberton Autopilot on the Patience. The Simrad/Roberton is fully NMEA 0083 compliant and will interface with VNS. In other words, VNS will tell the autopilot (through the NMEA language) where the next waypoint is and the autopilot will do best job it can to get the boat there. After the boat reaches the active waypoint, VNS will start instructing the autopilot how to get to the next waypoint in the route. People who are against this technology make the argument that having an autopilot and the computer pilot the boat with no human involvement is dangerous. The reality of the situation is that human involvement is a critical element of the autopilot/computer interface. The human is still responsible for creating the routes, standing watch and in many cases, approving any course changes. Most people have nicknames for their autopilots, for instance, ours has always been “Magic Mike”. Presumably people name their autopilots because having a pilot is like have an extra crewmember onboard—one who doesn’t take up a bunk, eat, or complain. The problem with Magic Mike is that he is kind of dumb—he doesn’t know where our end destination is, he doesn’t know when we have passed a waypoint. Interfacing your autopilot with VNS is like sending Magic Mike to a top-notch navigation school. After graduation, Mike is a lot smarter. While he still can’t take the boat to Mexico for you, he is a heck of a good man to have around. Prior to interfacing our autopilot and VNS, I used to manually try and set the old autopilot to follow the active route on VNS. Eventually we would stray off the route and I would have to re-adjust the autopilot. This process went on constantly, resulting in a “wiggly” course (see diagram to right). When VNS is interfaced with our Simrad/Roberton pilot, they steer a much straighter and more efficient course than I could ever hope to. In addition, sometimes VNS and the autopilot are able to steer a truly better course than the average helmsman. A situation comes to mind in Alaska where we were running across a large body of water with a 1+ knot tidal stream. VNS realized that our true course over the bottom was being affected by the tidal stream and adjusted accordingly. Visually, our heading (or where the boat was pointing) looked incorrect—it seemed we were going to run into a headland if we continued on the VNS-inspired course. Ultimately though, the effect of the current pushed us “downstream” and we ended up at the correct place. Perhaps a really on-the-ball helmsman would have graciously accounted for this, but I wouldn’t have.
TGW.NET is property of Tim Whelan. All pictures, diagrams and text ©Tim Whelan 1980–2002, all rights reserved. Only permitted images and material may be downloaded from this web site. For usage, please see my copyright notice. | |
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"Magic Mike", our autopilot,
steers a much better course
than I can, when he is hooked
up to VNS. |
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