GPS oddity

[masshysteria]

I have this weird problem that keeps occuring with my Garmin E-Trex Vista. Whenever I download the track from a hike I've taken to one of my mapping programs, I end up getting this line on the map.It extends from where I turned the GPS on to where I ended my last hike. The problem is that I make sure to delete all routes, track logs, waypoints and hiking data when I start. The slate should be clear, yet the GPS has that last tracklog in its memory.
When it does show up on the mapping program, it's just a matter of splitting the ghost line off and deleting it. The ghost line becomes part of my hike info, which distorts the mileage, elevation changes, etc..
Is this a GPS issue, or perhaps a mapping software problem? I'm using NG Topo with the GPS. Thanks for any suggestions.

 

[Rick]

Mass Hysteria -
I am going from memory here.
I think you are navigating from an old position and the line is a direct line to that postion from your current position that gets downloaded along with your waypoints. Also are you selecting everything to download or just the waypoints from your trip.

If the line is also appearing on your GPS, then before you download next time, Try cycling over to the Navigation page and using the thumbstick, click on the options menu at the top (the one on the right) and the options will drop down. scroll down to "Stop navigation" and click on that option. Hope this helps.
good Luck
Rick

 

[swamp]

I have a Vista and have another strange problem. Every so often the GPS decides that it's thousands of miles from it's actual location. This past weekend I was using it on a whack of Big Coolidge in the Whites. I had the summit waypointed and occasionally checked my progress on the Vista. As I approached the summit I again checked the GPS and it had me six hundred and some odd miles away. By zooming out the map I determined that the GPS had me in the Atlantic about 400 miles off the coast of the Carolinas. I've been lost before but not quite that lost.
This is the third or fourth time that this has occured in the last 2 years. I've kept the software up to date off the Garmin site and just can't figure out what would cause this problem.

 

[Pucknuts61]

One possibility is that it's a route. I find that if I set my route up using waypoints while hiking, it appears as a straight line. I end up deleting those and just sticking with the "tracks" and then using my software to retrace those tracks to make the actual route.
It's easier to use the software to map the routes than to use the unit itself to do it (at least with the Etrex).

 

[DougPaul]

I have a Vista and have another strange problem. Every so often the GPS decides that it's thousands of miles from it's actual location. This past weekend I was using it on a whack of Big Coolidge in the Whites. I had the summit waypointed and occasionally checked my progress on the Vista. As I approached the summit I again checked the GPS and it had me six hundred and some odd miles away. By zooming out the map I determined that the GPS had me in the Atlantic about 400 miles off the coast of the Carolinas. I've been lost before but not quite that lost.
This is the third or fourth time that this has occured in the last 2 years. I've kept the software up to date off the Garmin site and just can't figure out what would cause this problem.

This is normal. Every now and then in bad signal conditions or when starting up, a GPS will get a really bad position fix. Such bad fixes are generally pretty easy to recognize.

Doug

 

[Mark]

This is normal. Every now and then in bad signal conditions or when starting up, a GPS will get a really bad position fix. Such bad fixes are generally pretty easy to recognize.

Doug

Huh. I've had an eTrex Summit for years now and never seen this behavior. I thought the software was smart enough to toss out data that is obviously incorrect. Are you up to date on software versions?

 

[DougPaul]

Re "ghost" lines.

(Never heard them called ghost lines, but it seems like as good a name as any...)

These happen when the GPS is moved while turned off. Either the GPS or the computer software connects the points before and after the off period and creates the ghost line. On a large scale this can be annoying because it can connect unrelated tracks, but on a small scale it can fill in short gaps in a track.

Not sure whether the GPS or the computer software is doing the connecting.

One thing to try to elminate the ghost lines would be to get a fix at the new trailhead and then erase any old stored tracks. This would hopefully flush any memory of the previous hike.

I would guess that if you finish hike 1, turn the GPS off, go home, erase the tracklog, go to trailhead 2, turn the GPS on, and begin hike 2, the GPS could start up for hike 2 thinking it started at the end of hike 1 (or home if a fix was obtained while erasing the tracklog) and would insert a ghost line. (This may be similar to Rick's suggestion.)

Doug

 

[DougPaul]

Re: very bad location fixes

Huh. I've had an eTrex Summit for years now and never seen this behavior. I thought the software was smart enough to toss out data that is obviously incorrect. Are you up to date on software versions?

How often it occurs depends on the conditions in which one uses the GPS. It is generally fairly rare. I've seen it a few times myself in tracks, don't recall seeing it live on the GPS realtime display. I personally consider it to be such a non-event that I just notice it, mentally filter it out, and forget it.

The easiest way to observe it is to look at recorded tracks--every now an then a track point is way out in left field (and the GPS may record a maximum speed of hundreds of mph as you zip out the the bad location and return in a few seconds).

The software might be able to filter out a small number of bad points, but if it gets too aggressive, it will start filtering out good points as well as bad points. Remember, the GPS doesn't know that you are walking. For all it knows, it might be sitting on a rocket being moved slowly on a transporter until the rocket is fired and it suddenly moves at hundreds of mph.

This problem is primarily caused by bad signal conditions--the software version has little to do with it. (Of course, software bugs could create bad fixes, but it can occur without the help of bugs.)

Doug

 

[masshysteria]

Thanks for all of the helpful suggestions. I'm going to give Dougs suggestion of clearing the memory again when I start the hike a try. FWIW, when I'm at the computer and I turn the GPS on to download waypoints and routes, the first thing I do is to put it into "use with GPS off" mode. It shouldn't have enough time to make a satelite connection, but maybe I'm wrong.

 

[DougPaul]

Thanks for all of the helpful suggestions. I'm going to give Dougs suggestion of clearing the memory again when I start the hike a try. FWIW, when I'm at the computer and I turn the GPS on to download waypoints and routes, the first thing I do is to put it into "use with GPS off" mode. It shouldn't have enough time to make a satelite connection, but maybe I'm wrong.

If you haven't used the GPS in a while, it will be performing a "cold start" which takes 30-45 seconds (or so). Should be enough to go to no GPS mode. Another trick would be to hold your hand over the antenna--no signals to lock onto.

Let me (or the thread) know how my suggestion works--it is just a (hopefully educated) guess.

Doug

 

[MichaelJ]

When you start your hike, make sure that after you get a signal lock, that *then* you go and clear track memory and navigation information (max speed, mileage, etc.)

Otherwise, it's "starting" you at an unknown location to it, then getting a lock and jumping you to the trailhead.

 

[masshysteria]

I'll be going to the ADKs later this week, so I will let you know. Thanks.

 

[CaptCaper]

When you start your hike, make sure that after you get a signal lock, that *then* you go and clear track memory and navigation information (max speed, mileage, etc.)

Otherwise, it's "starting" you at an unknown location to it, then getting a lock and jumping you to the trailhead.

Yes I agree get locked on first. Also check to make sure the software is up to date in the GPS. I thought I remember something about that in some of the updates Garmin had out.

 

[masshysteria]

Just last month, I downloaded the newest updates from the Garmin site, so I should be good with that.

 

[Brownie]

I have downloaded and uploaded GPS data for at least a hundred hikes and other activities, into both NG TOPO and Garmin software for PC.
Using both Garmin Etrex and now the advanced 60CS, I have downloaded data from each unit, from the same trips, and got the same results.

The GPS does create a waypoint back to last signal acquisition when turned off and can be aborted by using the "use with GPS offline" mode when downloading to PC.
The Garmin Mapsource software often is smart enough to ignore this last waypoint and "ghost line" mentioned, but the NG TOPO is not.

About false GPS readings in general:
The Garmin Mapsource software will give you the opportunity to edit tracks as desired, right down to each individual satellite acquisition point.
When you display the list of tracks, you can then click on each track and get very detailed info for speed and position. From that interface you can delete erroneous data acquisitions and straighten the actual path.
Lost GPS signal tracks will show up as broken tracks not linked.
This is a bummer if trying to expect to reload it back to GPS for future reference.
In that case, best to redraw a route on PC, overlaid onto actual track data collected, then upload that info to GPS. This method also helps to identify the ACTUAL trail vs, the MAPPED trail differences.

NG Topo:
This software will show that "ghost line" as mentioned, however it will fill in a track line continuous if signal data was lost. This is good.

Both software work great, but neither is perfect or can be expected.

Jeff

 

[CaptCaper]

NG Ghost Lines

I agree with Jeff.

What I have come to do is turn unit on and acquire a fix clear track,etc. when done shut off while still on fix. I also use a high gain small antenna so I don't lose signal at all during hike.
When turning on to load data after hike hit the menu quick and select "USE WITH GPS OFF" and turn the track log off thus giving it a chance to start laying track points every where.

I got a ghost line the other day in NG TOPO. What I do is magnify the map 200% and right click where it meets the real track and select split route here.
Then I delete it. You can do this more as needed.

Mapsourse will allow you to delete the points you want then you can load the track to gps again then to NG for a clean track line for viewing.