I have a Garmin 76Csx. Great unit.
I rarely use it for navigation but have used it in the past for those hard to find passages in which case it has been very useful.
On my last trip when I went up to Candada I used it to try to find a small passage that was like threading a needle and it really screwed me up.
I was using it in the navigation mode and it was pointing me in a direction that did not make sense to me but I trusted it and kept going farther up the shoreline until I knew I had gone to far.
I noticed that it was pointing me in that direction but as I continued in that direction my distance from my destination was increasing instead of decreasing.
I then went to the map mode and it contradicted the navigation mode showing that I had to go in the opposite direction.
I used it both with and without the electric compass mode one, but still had the same problem.
I found the passage, but would have found it sooner if I had not tried to use the GPS.
Any ideas on what would cause this?
Bottome line was that the navigation mode and map mode showed 180 degree difference in which way to travel and in the nav mode when traveling in the direction it was pointing you were actually getting farther and farther from the destination. Turning 180 degrees from the arrow resulted in the opposite.
thanks
Matt
which destination?
Was your go-to point the passage itself, or some point beyond the passage such as your final destination?
GPS nav mode at kayak scale…
… is not much use, in my experience. On a complex path (through twisty shoals), I set waypoints every few hundred yards. But whenever I wasn’t aimed directly at the next waypoint, which is often considering the slop in the points, it said to go in a nonsense direction. Sounds like that happened to you too.
As you found, I think it’s best to use the map on the Garmin mapping units instead of nav mode. Nav mode is meant for big boats going much faster, with waypoints set much farther apart. Even for those, however, I bet the same thing happens when you get near the next waypoint. Say you are heading north and approach the next point slightly to its west – it then tells you you gotta go east to hit it, when you really want to keep going to the next waypoint, say north-northwest.
Thinking about it that way, in a kayak with a twisty path, you are ~always~ near the next waypoint, so you always get the local error problem.
I think Garmin could solve the problem in software by allowing you to set a “circle of tolerance” around each waypoint. But then it would all get even more complex.
Also…
… one more thought…
In a powerboat going reasonably fast, as you approach a waypoint a bit off, the bogus direction from Nav mode will last a very short time. You’ll quickly pass the waypoint, the nav software will pick up on the next one, and the erroneous instructions will be replaced by instructions to the next point.
In a kayak, however, at 2-4 knots, you will spend a lot of time looking at that spurious direction, which is trying to get you to hit the waypoint on the nose when you really just wanna keep going to the next one.
Help Me Out Here
What exactly is nav mode? You had waypoints entered and were doing a “go to”?
I bought a MAP76 several years ago and bought the Atlantic Blue Chart software. It’s fantastic for getting through maze-like salt marshes.
In nav mode…
… you activate a numbered sequence of waypoints that you have set on the unit or downloaded. (I have a way of making them in Google Earth and then downloading them – works great for navigating around tricky shoaled areas like the west side of of Monomoy in the Cape.)
The GPS unit then tells you which waypoint is next, how far away it is, and what direction you have to go to hit it (in the 8 compass points, unfortunately; can’t find a way to make my GPSMap 76CS do it in degrees)
The complications we are talking about (at least I am) happen when you do not hit a waypoint sufficiently close, or don’t take a straight path to it. Then the unit can act confused, and direct you in a funny direction to hit the waypoint exactly, which might be 90 or more degrees off what you think is the course, including sometimes even going backwards, until it decides it’s OK to go on to the next one.
I haven’t quite figured out what its algorithm is for deciding which waypoint to direct you to (perhaps the closest). But the solution is to use the map screen, where the waypoints show up, and navigate more “manually” from that.
And yes, it the unit is great for finding your way around marshes, shoaled areas and similarly intricate places. You may not even want to bother with nav mode in a kayak – as I said, I think it works better for a faster boat.
Thanks
The mapping was expensive but sooo easy to use.
agreed
Agreed, mapping mode, and I assume you mean with tracking activated, is the shiznit of gps. (For non-gps’ers, the unit displays the relevant map of where you are with a separate colored line which tracks your progress, and as you advance the screen advances to keep your position centered.) It is, after all, essentially the impossible-to-fully-achieve standard that we used to aim for with map and compass navigation, only now it’s achieveable with ease, exactitude and certitude.
(Until the battery dies.)
(Until the battery dies.)
Bingo!
PS: I've now gotta pad the contact ends of my battery slots with aluminum foil. Otherwise, the batteries are too loose. They jiggle in transit, break electrical contact, and shut down the unit. When I put it in a hatch just to record a track -- on a paddle that needs no real navigation work -- I often find that it shut down during the trip, sometimes as early as right away, and did not record a track. Shoot!
The aluminum foil padding on the contacts fixes that, but is a huge nuisance when I have to change batteries, especially en route.
Have You Tried…
bending the contacts a little?
Bending them is tricky
Three of the four contacts are just thin pieces of folded metal, and the fourth is a wimpy spring. The metal is folded with the open end down in the bottom of the battery case, so it's hard to get under them to bend them out. Also, I don't think it would increase pressure much. They would tend to bend back, and after doing it a few times, the fold might weaken with metal fatigue.
I think the solution is to get some aluminum foil -- or almost anything -- wedged more or less permanently inside the fold, which is tricky.
Thanks for the suggestion.
responses…
In response to a few questions raised…I was navigating to a single point…the launch site. In order to get to the launch site there was a small passage and stream that you had to go up for a short distance.
I do realize that GPS units have weaknesses for this given that they point you in a straight line / shortest distance and not along the route that you would take, but in this instance I think it was good enough as an aid.
I agree that the pointer is scaled for higher speed, but its not too bad. I have practiced with it on the ground walking (geocaching) and it works fairly well at slower speeds.
I also understand how the GPS gets confused when you are really close to the point and starts pointing you in all kinds of opposite directions.
In this case I was still maybe a half mile away from the point and what was strange was that the unit was contradicting ITSELF by exactly 180 degrees.
My chart and intuition told me I had passed the point, but the GPS kept pointing me in that direction. I then looked at the “distance to point” on the GPS and noticed it was getting larger when I went in the direction it was pointing me.
When I turned around and went the opposite direction the arrow told me I was going 180 degrees in the wrong direction although the distance to the destination was getting smaller.
Using the map mode actually helped me to go in the right direction which was 180 degrees different from the navigation mode.
Seems like something was wrong in one of my settings or something. Being exactly 180 degrees out is kind of strange.
I figured that there might have been some sort of an easy explanation.
It’s the only time it’s happened to me, but it certainly wasted a lot of my time.
Matt
STOP!! Do not bend that one out!
Like you said, it’s hard to get anything under there to bend it out. But once you get under it and bend it just a little, it breaks right off.
Been there, done that.
Software bugs
> When I turned around and went the opposite direction
the arrow told me I was going 180 degrees in the wrong
direction although the distance to the destination was
getting smaller.
Software bug – plain and simple.
I’m in the software development business, and I assure you that all programs have significant bugs, design flaws, misleading or klunky interfaces, etc. In particular, I’ve found that the mapping industry software quality standards are pretty low.
Well, there are exceptions. Medical devices, manned rocket systems; etc – all tend to have a lot better software – and well they should, with lives at stake. That’s because the government mandates quality standards, and the money spent testing for bugs often exceeds that spent writing the programs in the first place.
nimh rechargeables
I’ve found that at least some nimh rechargeable batteries tend to be just slightly snugger fitting than alkalines. Enough so that lost contact issues go away when using them even in high-vibration conditions.
My Standard Answers
When the computers at work lose their minds I usually lay it on magnetic anomolies or sunspot activity. Singularities are good, too.
“Dude, you came too close to the Chesapeake singularity.”
Calibrated?
Did you calibrate the compass? Units with an electronic compass need to be calibrated every time you change the batteries and sometimes in between if it has sat around for a while.
If you don't calibrate it you will get strange readings on the compass navigation screen, including pointing in the wrong direction
I believe your response points out …
what you did wrong.
You were “navigating to the launch site”, and the GPS was doing what you asked it to.
It was directing you to go the straighest route.
You should have been using the “track back” mode in which case it would have led you back the way you came.
the other mistake you made was not punching in a way point as you came out of your cut. Then when you reached your turn around point, you could have created a “route” back using that as one of the points prior to your home point and it would have brought you to it.
They are a wonderful tool once you learn all their intricaces
Cheers,
JackL
Garmin compass headings
> The GPS unit then tells you which waypoint is
> next, how far away it is, and what direction you
> have to go to hit it (in the 8 compass points,
> unfortunately; can't find a way to make my GPSMap
> 76CS do it in degrees)
Press the Menu button twice to get to the main menu; select System, and then select Heading. This allows you to use cardinal points, degrees, or mils (for whatever purpose), as well as True or Magnetic.
The other settings on the "Heading" setup page specify when to switch to the magnetic compass instead of the GPS compass: going below some speed for however-many seconds you like.)
Off-road navigation
> I think Garmin could solve the problem in
> software by allowing you to set a "circle of
> tolerance" around each waypoint. But then it
> would all get even more complex.
There is a setting that may help with nautical navigation. I've not used it, but hope to.
On the Routes page (the list of planned routes: normally you get to it by pressing Menu twice, then selecting Routes), press Menu: it gives a choice of .... maybe delete all, and "Off-Road Transition...". Select "Off-Road Transition..."
This allows you to select "Auto" (which I hope means automatic and not automobile), "Manual", and "Distance".
Auto: figures out when you've passed a waypoint by itself.
Manual: on the Active Route page (showing waypoints, distance to them, etc.: I've only used this on-road, so I'm not sure what it says off-road.), you can use the "In" zoom button to tell the GPS to navigate you to the next waypoint, or the "Out" button to navigate back to the previous point. (I may have these swapped: the GPS is down in the car.) This allows you to manually say, "I'm here, take me to the next place."
Distance: specify that when you are within some distance of a waypoint (the "circle of tolerance" someone mentioned in a reply), that counts as "good enough", and you want to aim to the next one.
Also, the comment on calibrating the compass is important, as well as the possibility of a software bug. Also, were you sure you had the electronic compass going? It may have been using your GPS readings as your current direction. (Ah, that's the other setting on the "Heading" setup page: when to switch to the magnetic compass instead of the GPS compass: going below some speed for however-many seconds you like.)