How close is close

[whisper]

Re: Still no answer to the original question

Right then "experts", I have a Furuno GP32. I often start my trips full of good intentions and put in a route from Salcombe to X. Regularly, I get bored with this after a couple of waypoints and so take a short cut/diversion thereby missing out a waypoint by about half a mile to a mile. The Gps does not automatically send me to the next one so I have to revert to the "go to" method which then supercedes the route that is entered. I can't find any reference in the instruction book that tells me how to return to my original route if a waypoint is missed. Any ideas ?

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[BrendanS]

Re: Still no answer to the original question

I'm no expert in other than Garmin. I'd say that what Gludy considers as dangerous would be ideal for you circumstances? Garmin units would just take you to the next leg

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[Gludy]

Re: Still no answer to the original question

All I can say is that on my unit you can return to the original route by placing your cursor over the next waypoint you want to head to and clicking on "Follow from here".



<hr width=100% size=1>Paul

 

[kimhollamby]

well, if I was writing the article...

...that I think some would like to see come out of this I would do that. It's exactly the approach I took when trying to ID which manufacturers used rhumb line or GC (or both) but that was a hell of an experience in itself.

Predictably enough what you do find is that previous generations of programmers take a certain amount of knowledge with them when/if they leave companies. So the finer points not documented in manuals are sometimes hard to come by; typical ITesque disease.

Having had a look at the Garmin's manual for this thread I have to say it is not exactly explicit in the way the unit works; or if it is I was searching the wrong keywords on the PDF or just didn't look hard enough. My guess from what I read is that it works on a time or distance proximity basis.

That said Garmin I would anticipate being a fairly easy telephone call because there seems to have been a rigidity to its approach that is almost unique, or has been. I believe Raymarine is now trying to go that way, but it uses cartography from C-Map and Navionics (which in itself causes issues because the underlying operating system, while modified, comes from those companies) and has, in its Raytheon life, had developers sat both sides of the Atlantic. Put a the 10in 630 plotter alongside a 7in Pathfinder of the same period (all circa about four years ago) and you'll see big differences.

So it ought to be done, but it would be a waffly and not completely comprehensive list I suspect.

I'm not currently being asked to write any tech stuff for any of the titles (I think there's a sinister theory afoot that I have enough to do) but I will draw the attention of various interested parties to this thread.

Ultimately, as we did with GC/RL issue and also chart datum, some on water testing/observation would be appropriate too.

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[Gludy]

Re: well, if I was writing the article...

Kim
I mainly use the RayMarine plotters - leatest versions.

These work using the 90 degree (not bisection angle as with Garmin) but they work well and issue a warning about the fact that you have passed the wayoint albeit with a large XTE and leave you with the choice to go onto the next waypoint.

This is very handy for taking detours (having checked route safety) and still using the route albeit that you have diverted slightly.

I think Raymarine have it right - the manuals also explain it OK.

I have a Garmin Map76 as well, so I will check that out once more and report.

<hr width=100% size=1>Paul

 

[lanason]

Garmin OFFICIAL reply

This is the reply I have now rec'd by e-mail from Garmin.

Dear Sir,

All of the new ARM software units, (eMap, eTrex family, 295, 162/168) are using a new algorithm to calculate ETE/ETA.

The new algorithm has a number of filters built in to take into account changes in speeds and course to "learn" the navigating behaviour of the unit. This will give better relative accuracy as well as smoother behaviour in the output readings.

In the old software, we have a finish line that is at a right angle to the projected direct course-line. In the new software, we calculate a 45 degree angle to the destination waypoint.

This, coupled with the filters which are averaging heading and speed produces a much more conservative reading, while also allowing for greater overall accuracy.

As for the change over form one way point to another this occurs when you cross the bisecting line between the two way points. In other words to cross over you do not have to be near the waypoint, just cross the bisector. I am not sure how much sense that makes without a diagram.

You can draw you own conclusions.


<hr width=100% size=1>Adrian - <A target="_blank" HREF=http://www.arweb.co.uk/argallery/kelisha>More Pics of Kelisha</A> /forums/images/icons/smile.gif

 

[BrendanS]

Re: Garmin OFFICIAL reply

>>As for the change over form one way point to another this occurs when you cross the bisecting line between the two way points. In other words to cross over you do not have to be near the waypoint, just cross the bisector<<

Which is exactly how I said Garmin units worked



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[Gludy]

Re: Garmin OFFICIAL reply

Its what O have been claiming all along - despite the fact that the Garmin handbook does not state this at all - so leaving the user without any understanding of how it changes over from one waypoint to the other!

Raymarine also operate in a similiar way - but how many others do without telling you?

What about a question to Furuno and Simrad?

<hr width=100% size=1>Paul

 

[Observer]

Re: Garmin OFFICIAL reply

Hmm. Well what exactly is "the bisecting line between two waypoints". Doesn't make sense to me. Does it mean the line through the current waypoint at right angles to the original course line or at right angles to the current bearing line or neither of those.

As I remember, the Simrad GPS unit on our old boat transferred to the next waypoint automatically when the line at right angles to the course (or bearing) line was reached.

Personally, I don't see it's a big deal whether it's automatic or not, if it's just acting as a GPS/plotter, as long as the user knows which applies (and even then it could be argued the user should be monitoring XTE so know whether a problem may be looming or not).

Where the GPS is linked to the autopilot, that's a different matter. In that case, the autopilot should invite confirmation of a course change, but that's an autopilot function, surely, not a GPS function.


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[BrendanS]

Re: Garmin OFFICIAL reply

No, not right angles, the line that bisects the two legs. See the garmin link I posted elsewhere in the thread, and it takes you to the Garmin site to the page where there is a diagram.

The discussion was not about whether it automatic or not, but how the unit determines when to go to the next leg. Not many people realised it was by the bisecting line or similar method, and there was confusion between this method, and what proximity alarms were for (different thing entirely)

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[hlb]

Re: Still no answer to the original question

Can you not tell it to go "Forwards" To next way point??

<hr width=100% size=1> <font color=blue>No one can force me to come here.<font color=red> I'm a volunteer!!.<font color=blue>

Haydn

 

[Observer]

Re: Garmin OFFICIAL reply

Ah yes. I see now thank you.

I thought Gludy was "discussing" the "automatic advance or not" issue quite a lot -earlier on. Sorry if I didn't follow the discussion had moved on.

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[Gludy]

Re: Garmin OFFICIAL reply

I was discussing the means by which the gps unit decides to progress to thye next waypoint and as a follow on - the fact that units shoulkd always seek permission to go to the next waypoint.


In effect the right angle or bisected angle methods are really "Missed Waypoint" alarms.

<hr width=100% size=1>Paul