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SOG vs DSC VHF Decision

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Capt. Kurt
Navigator

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185 Posts

Initially Posted - 01/27/2006 : 16:11:50

I am trying to decide whether to connect GPS NMEA output to the ST60 depth meter for speed over ground (SOG) or connect to Ray54 VHF DSC for position data? Any opinions on what is more useful?

Thanks,
Kurt
#818 C250WK 'Tortuga'

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Tom Potter
Master Marine Consultant

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USA
1913 Posts

Response Posted - 01/27/2006 : 20:54:48

Hi Kurt, I hooked up my backup garmin 12 handheld to the VHF for DSC.

Its on the bottom under the swing arm bracket.

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Arlyn Stewart
Master Marine Consultant

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2980 Posts

Response Posted - 01/28/2006 : 05:01:08

Kurt, I'd think it would be useful to do so, especially since it isn't hard to do.

Another thought depending on the ST 60 repeat abilities is to also benefit from xte (cross track error) display if you do any cruising. Even though I run a base mounted gps with a reasonable sized screen, the screen of preferance is the compass rose but that screen does not offer xte data. Fortunately however the autopilot screen will pick up the xte from the gps and repeat it. It may seem odd, but I never use the compass screen on the autopilot head, it is always set to xte, here is why.

For the cruiser of an area with rocks and shoals, the safest navigation method is point to point with a known safe rhumb line between the points. XTE data is used to stay on line. Here is an example. Let us say that we are sailing from point A to point B twenty miles away and that there are no hazards between but at ten miles out or half way, there are shoals two miles to starboard of the rhumb line. If simply sailing the course from A to B on a port tack, leeway very well might place us onto the shoals. Even if sailing the constantly updated GPS course to B, the track will be curved and could put us on the shoal.

Needed is to watch the XTE and note how far to port or starboard of the rhumb line the boat lies. And, its not just about staying off hazards, the rhumb line is a straight line and a straight line is the shortest distance between two points so XTE data provides the quickest passage.

Why am I not interested in the compass screen on the autopilot? The course from the fluxgate compass is relatively useless because it tells the boat pointing rather than boat track, which are generally at odds with each other and it is the track that is of value.

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.