Hippocampus
Guru
- Joined
- Jul 27, 2020
- Messages
- 4,178
- Location
- Plymouth
- Vessel Name
- Hippocampus
- Vessel Make
- Nordic Tug 42
Comments about which compass the AP computer is using are critical to function. Even with multiple GPS sources the AP picks one as “master” and the others aren’t used so not relevant. Commonly the AP has its own compass and GPS independent of what else is on the network be it 2000 or older. TT’s point is quite relevant however. A satellite compass is usually more accurate if properly installed. Given GIGO that matters. It
being concerned about great circles and the error of Mercator projections isn’t relevant to a coastal cruiser but errors from using autoroute functions maybe. To circumvent the inadequacies of my new generation simrad I show the autoroute on the potter but don’t use it. When in tight quarters like the ICW, hellgate, inner NYC and such I don’t use waypoints or autoroute but rather ND with my hand on or near the small wheel on the AP control module. In effect I’m not hand steering but rather making frequent corrections to avoid debris and find deepest water when necessary. I find this least laborious. In larger, emptier bodies of water I do go way point to waypoint.
Still with each wave you are thrown off course. My AP is dumb. It does not anticipate the waves let alone wind gusts. So it wanders a bit except in flat water. However on the order of 6’ or less. That was the same on prior boats with Raymarine or B&G suites and older electronics. On rare occasions GPS was degraded (usually by the military is my guess from where we where). But your error is unacceptable and should be tracked down. Simple things like mechanical troubles such as a loose or poorly functioning rudder angle indicator. Or metal near a non satellite compass or loose attachment. Go through each component of your system and investigate if there’s anything obvious. If not you may want to call in a skilled tech,or simply replace an old system. Sometimes replacement ends up less expensive. View the AP as a key system to safety and comfort. We exclusively do single person watches and often single hand. A inaccurate AP is both dangerous and makes for a very long day.
being concerned about great circles and the error of Mercator projections isn’t relevant to a coastal cruiser but errors from using autoroute functions maybe. To circumvent the inadequacies of my new generation simrad I show the autoroute on the potter but don’t use it. When in tight quarters like the ICW, hellgate, inner NYC and such I don’t use waypoints or autoroute but rather ND with my hand on or near the small wheel on the AP control module. In effect I’m not hand steering but rather making frequent corrections to avoid debris and find deepest water when necessary. I find this least laborious. In larger, emptier bodies of water I do go way point to waypoint.
Still with each wave you are thrown off course. My AP is dumb. It does not anticipate the waves let alone wind gusts. So it wanders a bit except in flat water. However on the order of 6’ or less. That was the same on prior boats with Raymarine or B&G suites and older electronics. On rare occasions GPS was degraded (usually by the military is my guess from where we where). But your error is unacceptable and should be tracked down. Simple things like mechanical troubles such as a loose or poorly functioning rudder angle indicator. Or metal near a non satellite compass or loose attachment. Go through each component of your system and investigate if there’s anything obvious. If not you may want to call in a skilled tech,or simply replace an old system. Sometimes replacement ends up less expensive. View the AP as a key system to safety and comfort. We exclusively do single person watches and often single hand. A inaccurate AP is both dangerous and makes for a very long day.
