Garmin eTrex GPS - Active Track vs. Saved Tracks
I’ve got a Garmin eTrex GPS receiver — one of the cheapest, simplest units I could find, and I’ve been using it to record the routes that I drive for about a year now.
Previously, I would turn the GPS on, wait for it to find satellites and be ready, then make my trip. iI have the track recording feature on, recording every ~54ft or so (some decimal fraction of a mile.. I guess that would be 0.01 miles). Eventually, when the “active track” log was getting full (since it shows percentage full), I would download the data to my computer and save in two formats (to be safe): G7T (because i was using the program, G7ToWin), and GPX (because Google Earth can read that). Those data files contained coordinates and time at each 0.01 mile point. So, given the right parser, I can analyze those files later, to gather stats on my trips from one point to another.
What I discovered recently, though, is that a recent change in my track recording procedure was flawed. When I import my GPX file into Google Earth, it draws the active track, which may be a combination of 5-15 different actual trips, recorded on different days, etc. It reads it as just 1 track, and the playback feature in Google Earth is not very configurable, so I had to start with the very first point in the track, and play until the point I cared about. Also, I kept filling up my active track log, because I procrastinated downloading.
So, I tried using the ‘Save Track’ feature in the GPS. At the beginning of each trip, I would clear the active track log, resetting the space usage to 0%. Then, when I reached my destination, I would save the track, which was (in theory) associating all of that data with a named track. Then, next time I drove, I would reset the active track (but my saved one would still be there, saved), and record again. Then I’d save that when I reached the destination, etc. Eventually, when I ran out of saved track slots, I had to download them all, then delete them all from the GPS to clear it out.
The saved tracks provided separation between trips, so in Google Earth I could play back a single trip easily. But, apparently, saving the track only saves the location info, NOT that datetime stamps. That’s what I just learned the hard way… and that’s half of what I care about.
So, no more saving tracks for me, unless I specifically only care about location data, and timestamps don’t matter. Active tracks only. I have to just download every couple days, I guess. Stay on top of it. At least my data will be more useful to me, then.
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October 21st, 2006 at 12:13 am
Do you do geocaching?
October 21st, 2006 at 11:34 pm
Nope, never done geocaching. I just use my GPSes to keep track of where I’ve been and how to get where I’m going, when driving. More on that later.
October 30th, 2006 at 6:42 pm
Oops, I found this out the hard way too. I had planned to geocode a large collection of jpegs from my recent overseas trip. Oh well… :)
November 13th, 2006 at 3:09 am
Have just found this out the hard way as well. I just got back from a trip in the Peruvian Andes, and was planning to clean up a section of my track with a very high level of errors. The only accurate way I can think of to do this is by eliminating any points that would inidcate a velocity faster than I can walk over rough ground. Unfortunately no timestamps = no velocities; and I thought I was being so organised saving my tracks on a daily basis :-)
I’ll have to do some kind of statistical analysis instead…
December 8th, 2006 at 5:03 pm
Do you know where i could get my GPS service by cell phones?
my friends download GPS software to cell phones, and their phone become the navigation system. so cool! but, how i can get
one too?!