(used) Garmin Edge 305: should I expect more?
I just picked up my first GPS device: a used Garmin Edge 305 from ebay. I used it once on an almost-treeless road ride and the map looked accurate enough.
My second time using it, and neighborhood spin over to a wooded and steeply sloped trail netwrok has me wondering if this thing is faulty and whether or not I should send it back and ask for a refund.
- I pressed 'start' in my driveway, yet the ride file shows me starting about .65 miles from my house.
- I elevations for the first half off the ride showed me at ~220', but are actually 500'. the second half of the ride it got it right.
- I climbed and descended a trail, yet the route file showed my climb and descent as being about 1/8 of a mile apart for most of the trail segment.
I've heard these things lose signal in trees etc., but should my start point and elevation be that far off? Did I get a lemon or are these things all typical?
thanks for any insight.
the elevation does vary sometimes.
Originally Posted by phreadi
But it sounds like you did not let the unit to get a solid satellite lock before you pressed start. Even after the unit has a basic lock it can take a few minutes for the readings to settle down.
May also need to reset the sampling rate (forgot the term Garmin uses).
Tree cover can affect the signal, especially wet leaves. IME the Edge 305 is more accurate than most GPS units overall
The trouble with common sense is it is no longer common
You can't just turn it on, immediately press start, and expect it to run without any problems. I did a 5k race with my Forerunner once where it took more than half an hour to get a satellite lock in an urban area after traveling several hundred miles from my last known location, and a couple weeks after using it last. You have to give it time to "warm up" and settle down like shiggy said.
Originally Posted by phreadi
The elevations do vary. Weather changes will affect readings, and the sort of calibration you use (and how often that happens) will also affect the readings.
The speed you travel will affect accuracy. I find that my tracks on a fast descent also don't line up with the climb on that same trail. Some sections will, but often times not.
What you see is fairly common. You could get slightly better results by modifying your use a little bit. But a GPS is not perfect. You should not expect flawless results.
Thanks for the feedback... I definitely noticed more accuracy on the climbs vs. speedy descents. i'll definitely let it do it's thing for a while first before starting next time.
As far as calibration -- is it just a matter of playing with it's settings, or are there 3rd party aspects to calibration I should know about?
Regarding fitness device elevation
DC Rainmaker: Understanding Sport Device GPS Elevation Issues
I use a handheld, and one advantage it provides is the ability to manually calibrate the altimeter to known points (like peaks, passes, USGS benchmarks, etc).