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ChiefPig

Garmin (etrex) Tracklog/Trackback

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I have a Garmin eTrex Legend.

 

It seems that the Trackback feature is not smart enough to determine that you are already halfway along the track. In other words, if I went to a cache with my tracklog on from the parking lot and then halfway back from the cache to my car, I got lost in the trail, if I turn on trackback, it would try to navigate me back to the cache and then to the car instead of just navigating me from where I am back to the car.

 

Is this correct? Or am I missing something?

 

Also, when you save your tracklog, it gives you several options other than 'entire log' like different times (e.g. 4:00pm) or intervals (1/2 hour). Are these random times/intervals or do they mean something like when I last stopped or lost signal?

 

Thanks.

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quote:
Originally posted by ChiefPig:

I have a Garmin eTrex Legend.

 

It seems that the Trackback feature is not smart enough to determine that you are already halfway along the track. In other words, if I went to a cache with my tracklog on from the parking lot and then halfway back from the cache to my car, I got lost in the trail, if I turn on trackback, it would try to navigate me back to the cache and then to the car instead of just navigating me from where I am back to the car.

 

Is this correct? Or am I missing something?


When you activate TrackBack, it takes your tracking log and attempts to turn it into a route. It makes waypoints in places where you've altered your general direction. Once that's done, it works just like following any other route. Usually my Vista is smart enough to see what waypoint I'm heading for, and pick up the navigation from there. Sometimes, it's necessary to stop and re-start route navigation before it figures out where I am on the route.

 

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"Don't mess with a geocacher. We know all the best places to hide a body."

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So are you saying the etrex should be smart enough to know I am already halfway between the beginning and the end of the track and would just navigate me from where I am to the beginning? And maybe I should just stop navigation and restart the trackback for this to happen?

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It seems to me that it's doing what you ask it to do, i.e. bring you once again along the track. If I had done some loop in the track, I would like the unit to follow that loop, even if there is a shorter way.

You may be on the water, and the loop may be to avoid some obstacles in the water, for example.

 

Anders

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I am a new V owner and I can say this is definatekly a learning process...but the GPS will do what ever you tell it, which is good and bad.

 

When you hit "backtrack", it is telling the GPS "I want to go back exactly the way I came".....

 

Think about it : If you go from point A to point B and then start back to A again, and THEN hit "trackback", the GPS will track you back along the same route you took to get to where you are RIGHT NOW, which includes backtracking to point B and then to A after that...it is doing exactly what it was instructed....Probl;em is, we are "smart enough" to be able to add in teh added info that "we want to start from THIS point rather than back at B""....

 

I think a better way to do it would be to make sure you set waypoints as you go...and then you can route from one waypoint to another....this is in effect telling it where to start your backtrack from.....

 

quote:
Originally posted by ChiefPig:

So are you saying the etrex should be smart enough to know I am already halfway between the beginning and the end of the track and would just navigate me from where I am to the beginning? And maybe I should just stop navigation and restart the trackback for this to happen?


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You also need to tell your Legend if you want to trackback to the beginning or the end of the track. This will make a big difference in which direction the unit points.

 

Regards,

Mike

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I find it's easier to follow the trail on the map display rather than follow the trackback navigation. By looking at the breadcrumb trail you can make intelligent decision to avoid going back to the cache like in the example you gave.

 

Regarding the times given to create the "save" ffrom, i haven't figuredthat out either.

 

Anders?

 

Alan

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Looking at the map or following the trackback route, well, as long as it's done manually, it's up to you. But in the case where you have your GPS connected to an autopilot system in a boat (admittedly less likely with a Legend), it's a different ballgame. Then the unit must be navigating somewhere, to give the correct course to the autopilot unit.

 

Regarding the times given when you want to save a track:

In a Vista/Legend (and most other Garmin units, except the new Geko), the track is saved from the last point logged (which is where you are now, unless you turned logging off before reaching the current position) to the time selected from the menu.

The saving times menu gives the beginning of the three last track segments (seen as different Active log parts if you upload to MapSource), assuming that you have three segments in the current date. A segment starts when navigation has been off, either because you turned it off or because reception was lost (a not completely unlikely event with an eTrex).

The list also incorporates midnight and, if in the afternoon, noon.

Depending upon how many entries this created in the list, it may or may not include yesterday or one or more earlier dates. The option to save the whole track is also always there.

 

The new Geko has the pan-track feature, where you can pan along the track and set arbitrary start- and endpoints for the saved track. A much smarter solution, but not realistic to implement in a Vista/Legend, according to Garmin. Takes to much reprogramming for an old unit.

I've suggested the ability to include a marker, which you could set yourself at any time. Saving would then be possible to do back to the marker. Apparently, Garmin didn't like that idea, since it's nowhere to be seen at the moment.

 

In case you saved a track, but later realised that you didn't really get as much, of the track as you desired, or too much, you can upload to MapSource (or whatever), edit the track and download it to the GPS again. Thís will not help you if you want to backtrack whilst in the field, but if you are saving the track for some later occasion, it works. Also gives you the opportunity to edit the track, in case there are some spurious moves, created as a result of multipath, canopy, wicked users or whatever.

 

Anders

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What you are saying is partly true. If you go off course even a little bit, it will point you backwards. Practice this when driving and intentionally go off course and then get back on course. You'll see that it takes a little bit of time, but eventually readjusts.

 

I don't think it would work that well while walking due to the time delay but try it again and see as well.

 

Even though you enter the wrong waypoint....you're still in the right spot!

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I've so rarely used backtracking, so I can't really comment on how it behaves. On the other hand, I've followed conventional routes many times, and since a Garmin converts the saved track to a temporary route when you do the backtrack, I can't see that there ought to be any real difference.

I've not noticed any particular "backwards pointing" when following routes, except for a short moment, when passing a waypoint. As far as I've understood, when you pass a line that bisects the route through the waypoint, it will transfer guidance to the next waypoint. Which doesn't imply that it will point backwards just because you have some cross track error? It should simply point to the side, then transfer to the next point when you pass the current one.

 

Well, I have to go out testing a little, to see what happens to me and my unit!

 

Anders

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