Explorist Odometer Accuracy

[thanson]

Readings I get from the trip odometer on my Explorist 500 are roughly 20% less than indicated by trail markers and topo map estimates. When I upload track into MapSend it correlates closely to trail marker and topo map estimates - so it wouldn't seem I'm just perioidically losing satellite lock. Any info on whether the odometer is inaccurate or has a non-intuitive operation?

[+embra]

The odometer is fairly notorious for underestimating when moving at very slow speeds, like walking or canoing. It's not bad for driving. This is not specific to the Explorist, my Meridian had the same problem.

 

The best workaround I have found on my 500 in the field is to check the active track (menu/track log/hilight active track and length displays at bottom), which seems to have the same accuracy as what you find when you upload it to the PC.

[thanson]

Thanks for the info and the workaround. Interesting that this apparently long standing problem wouldn't have been corrected. Especially since Trip Odometer is one of the few items displayed on the non-customizable Position screen. If the track log is able to accurately track distance, you'd think as a last resort they could have tied into that data or algorithm.

 

So what is your confidence in the Speed indication at low speed? I suspect same issue is affecting this as well. My wife calls BS frequently when I call out our indicated hiking speed - she's adamant that we're going faster than indicated.

[+embra]

I haven't paid too close attention to speed when walking, but I wouldn't be surprised if it was unreliable as well.

 

One explanation I heard (don't know if it is valid or not) is that when moving slowly, the error in the position estimate gets to be such a large proportion of any actual change in position that the algorithms used by the Magellan don't work right. It does make sense to me that an error of 1mph in speed while walking is pretty substantial, while a 1mph error when driving 70 is small beans.

 

The tracklogs, laid down over every 50 feet or so (if set at .01 mi intervals) seems to get around whatever is screwing things up.

[+GOT GPS?]

I been having luck with the eXplorist XL, and I just took a tracklog off of it, and converted it to GPX format, and opened it in Garmin Mapsource, and G7ToWin. The Trip Odometer for the Run, shows 4.3 miles, and G7ToWin shows 4.38 miles, and Garmin Mapsource shows 4.4miles. This GPS has been quite accurate lately.

 

Edited IN: Next time I will try a slow walk, and see what the Trip Odometer does compared to G7ToWin and Garmin Mapsource, using GPS Babel to convert the eXplorist *.LOG files to *.GPX

Edited June 7, 2006 by GOT GPS?

[+Searching_ut]

I've found that in most situations recording trip distances while walking, hiking or running, accuracy of +- 10 percent or so is about the best you can hope for distance wise, with error rates for elevation being considerably worse unless your unit has barometric corection. Most of the trip computers on the GPS units have speed cutoffs to quit logging motion when the receiver thinks you're stopped, and they tend to use software solutions to compensate somewhat for the relatively small position errors the unit continuously suffers from. While relatively small, these errors can make a big difference to a slow speed hike. While driving longer distances at higher speeds they become such a small percentage of the overall distance traveled to be virtually negligible. With units that don't auto average, you can set it them up to record trackpoints every few seconds. Set the unit up to record like this, put it in a stationary position, then analyze the track after a few hours and you'll probably be surprised at how far it thinks it went. My GPS units have often taken quite the journey while simply sitting on a table outside.

 

That said, more often than not you can get considerably better results by editing and analyzing your track after the trip. Some software programs that simplify doing this and that do a large part of it for you automatically are:Topofusion and sportracks.. There are many other programs out there that do this, these are just the two I use more often than not for my hiking, running, and mountain bike trip analysis.

 

Finally, For slow speed travel, GPS units tend to not be very reliable for instantanious pace or grade sorts of measurments. When measureing total distance and average speed though the data tends to be much more accurate and useful.

[Rye_n_Coke]

Anybody heard if this issue is going to be addressed at all? I took my GPS hiking this weekend and thought there was something seriously wrong with it until I read this thread and realized that there IS something wrong with it, but at least it wasn't specific to my unit!

[+embra]

Magellan has always been pretty tight-lipped about what they are changing in the firmware. I'm not aware of any indication that they intend to do something about this.

[nrcooper]

I have an Explorist 210 that I use exclusively for hiking and snowshoeing. As such, the primary purpose of my GPS is to tell me my speed and how far I have hiked or snowshowed. Last spring, I hiked an 11.5 mile loop but my GPS odometer said I only hiked 8 miles. The vertical profile and download to my computer showed 11.3 miles which was very close to the trail documentation and signage of 11.5 miles. To check my GPS I threw it on the dashboard as I drove home and the GPS speed and odometer matched my trucks speed and odometer almost exactly. I thought I was going crazy!

 

After two emails and a phone call, Magellan told me to perform a complete reset and that would fix the problem. It took a while to get back out and hike again, but I still have the same issue. I emailed them again and again they told me to reset everything. Great solution.

 

I was so glad to stumble upon these posts and find that other Magellan users have this issue. I am going to try the suggestions in the above posts to see if I can at least manage the problem. I can not believe that Magellan can make a product with such a gross error. I love my Explorist 210 but if it is going to be this inaccurate and Magellan is not going to acknowledge or fix the problem then my next GPS is going to be a Garmin.