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New to GPS's and am getting strange results

Started by valfaroth, May 25, 2009, 05:31:43 PM

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valfaroth

I dont' know that these results are in fact strange but to me they seem really off.

I've taken my  GPS on a couple of hikes in the past couple weeks, and after hiking up to the end of the trail and back along the same trail, I notice the paths on my GPS don't match.  and they seem to be off by a LOT.

I'm new to all this so I'm not sure if it's some simple setting I'm missing or if I'm doing something wrong so I'm hoping for a little advice.  (Hopefully the answer is not a broken GPS 8)

If you check out my trail maps here http://www.everytrail.com/view_trip.php?trip_id=219189 you can see on Lake Serene, the trail seems ok from a distance but when you get close they are kind of wacky.  (Lots of craziness at the 3 mile mark with the switch backs.  And the path coming back doesn't show as the same path going up....it's off almost all the way.

Anyone have any thoughts?

GPS is a Garmin eTrex Vista HCx.

Thanks!

-Oz-

That is kinda odd that its that consistent.  Its normal for them to be off.  Lets say you have EPE (estimated positional error) of 20ft both ways that means really you could be 40ft off.
Dan Blomberg
Administrator - GPSFileDepot
GPS Units: Garmin Dakota 20, Garmin GPSMap 60csx, Nuvi 255W, Nuvi 250W, ForeRunner 110, Fenix 2, Tactix Bravo, Foretrex 401
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valfaroth

What would be the first step in trying to figure out the problem....Any suggestions?

Indrid Cold

I would first look into how I had my track logging set:

395 track points/8.08 Miles= 48.886138613861386138613861386139 points/Mile.

See: http://forums.gpsfiledepot.com/index.php/topic,151.0.html

valfaroth

I had it logging to a data card but it might have been set to "More Often" rather than "Most Often"...I'll give Most often a shot and see what Happens....

Does it take more battery power to go "Most Often" or is it just the amount of memory it takes up.

Could the paths be off up and back, based on different satellites being used?  (Really new to understanding how all this works.)

I'll give these a shot though...thanks.

(If anyone else has any advice, I'm still listening 8)

Huckleberry

I have the same unit (purchased about 1 month ago) and am thinking about doing a hike early next week.  What map set are you using (one from this site or)?

Also - I see that on another hike you had the elevation profile entered in.  Do you know if the elevation or any other differences were drastic between the two tracks?

Thanks -


valfaroth

#6
Quote
There was also a masking issue, especially with Mt. Index (5979') to the South and Philadelphia Mountain (4258') to the SouthEast. That's a problem with a Northern approach route in the Northern Hemisphere, the terrain can block WAAS corrections. Looks to me that you didn't have the best sky at that location for a perfect track.

That's interesting.  I hadn't thought of the mountains blocking connections....thanks for that.

valfaroth

Quote from: Huckleberry on May 26, 2009, 08:27:57 PM
I have the same unit (purchased about 1 month ago) and am thinking about doing a hike early next week.  What map set are you using (one from this site or)?

Also - I see that on another hike you had the elevation profile entered in.  Do you know if the elevation or any other differences were drastic between the two tracks?

Thanks -



I'm probably not the best to ask questions just yet, but I'll do my best to answer....Maybe someone else can help you more.

I have the Washington Topo map from this site.  That's the one I use.  As for elevation I havent' really paid too much attention to that yet.  I also heard that weather changes can change the elevation readings because it's a barometer.....Haven't looked into it too much.