how much variation is acceptable

[gitarmac]

My vista give longer distances than my venture, both are hc. The vista will say I am moving when I am really still for longer than the venture. I made sure my settings were the same tonight and walked around my block with my doggies. The block is about .90 miles long according to my car. I get about that when my venture is on my bicycle. I noticed at the hunt club the distance to my stand was longer with the vista but I can't say for sure how much.

 

So tonight around my block I got 1.02 miles for the vista, and 0.96 from the venture. The doggies like to sniff and stuff so I know that's going to throw it off, and even more for the vista.

 

But what I was not expecting was the track to be longer as well. I have the trackpoints set the same and would not think time would be a factor in that. There was a .05 mile differance.

 

Has anyone else ever compared differant units? How much variance would you consider acceptable, I guess any varience means one is more "accurate" than the other if the differance is always on the same side.

 

I'm going to try it in a car, when I'm moving at a better pace. At the hunt club I am not stopping when I track these distances, which seems to imply one of them is more "off".

 

Just wonderin'.

[seldom_sn]

My vista give longer distances than my venture, both are hc. The vista will say I am moving when I am really still for longer than the venture. I made sure my settings were the same tonight and walked around my block with my doggies. The block is about .90 miles long according to my car. I get about that when my venture is on my bicycle. I noticed at the hunt club the distance to my stand was longer with the vista but I can't say for sure how much.

 

So tonight around my block I got 1.02 miles for the vista, and 0.96 from the venture. The doggies like to sniff and stuff so I know that's going to throw it off, and even more for the vista.

 

But what I was not expecting was the track to be longer as well. I have the trackpoints set the same and would not think time would be a factor in that. There was a .05 mile differance.

 

Has anyone else ever compared differant units? How much variance would you consider acceptable, I guess any varience means one is more "accurate" than the other if the differance is always on the same side.

 

I'm going to try it in a car, when I'm moving at a better pace. At the hunt club I am not stopping when I track these distances, which seems to imply one of them is more "off".

 

Just wonderin'.

 

Make sure you have both units recording based on the same intervals. They are probably something like Automatic, Distance, Time. If one were recording at a fixed time interval, and one were recording at an "automatic" time interval, or a "distance" interval, it could have an affect on the overall distance traveled. A gps set to "measure by time" can move half a mile in an hour, even if its sitting in the same place.

[gitarmac]

I have both of the track settings set to "fewer". I am not sure about these other settings, what I have compared are the same.

 

I'll check when I get home and report back!

[+StarBrand]

That actually doesn't surprise me very much. I would set both units to a fixed unit of measure for better comparison but the etrex "h" units are all notoriously bad at slow movements.

[JDiablo]

I have both of the track settings set to "fewer". I am not sure about these other settings, what I have compared are the same.

 

I'll check when I get home and report back!

you might want to change fewer to most...

[gitarmac]

I just checked and the record method on both of them was "auto". The venture has always given pretty much the same distance around my block, or to my stands, and so does the vista, but the vista gives longer distances.

 

I think it has to do with the unit thinking you are moving when standing still, the vista is kind of bad about that. When I first got it it wandered A LOT!! I did the software updates (which you think would have been checked, since it was "factory refurbished" ) and a hard reset and it went back to reasonable levels.

 

I will experiment with those differant settings, maybe change them to "distance" and see what happens.

 

I still like them both though. I don't have any maps yet, I will probably really appreciate the differance then. I'm on the flat coast though, I wonder if the topo map will be useful at a flat swampy hunt club. The printed ones are all but useless. I make "maps" from satilite images.

 

We go to the mountains sometimes though, I'll bet it would be fun there.

[+twolpert]

I'm with StarBrand on this one. It's going to vary from model to model -- and some models are consistently better or worse than others. Getting this part "right" in the firmware is a difficult balancing act, especially with high-sensitivity receivers. On the one hand, you want accurate moving/stopped times and accurate distances. On the other hand, you're trying to smooth out spurious "motion" that's due to multi-path effects -- effects that are much worse with high-sensitivity receivers. Pretty sure it's a no-win for the poor programmer

[gitarmac]

I set out on a hike with both my gps's and experiemented with differant settings. To my surprize my venture, which has always given consistant milage for this hike, experianced a blip or something and added a half a mile or so, and said max speed was 80! Right before that the units were about identical.

 

On most tests the vista gave longer odometer readings. I'm not going to let this bother me though, it seems to be one of those things ya just gotta know about. That's why I am constantly trying out my units.

 

In spite of the innaccurate odometer readings, my gps's have never failed to get me back. Or away. Now I have the free topo map on the vista so that's pretty cool. I can't wait till we go to the mountains, COUNTOUR LINES! OH YEAH!

[+twolpert]

The "blip" is a fairly common artifact of multi-path errors with a high sensitivity receiver. As the unit switches among the various reflected signals from the same satellite, the position calculation will occasionally yield wildly different reported positions from one sample to the next. Usually, the differences are more on the order of 40 or 50 feet, but larger variations are possible. When this happens, the unit may record a very high speed for that "leg" of the track (since it thinks you went a long way in a short time), as well as adding the erroneous difference to the distance traveled...

 

Trying to smooth out these artifacts is what leads to errors in the distance travelled. If you smooth too much, the distance comes out shorter than it should be. If you don't smooth enough, these "blips" cause the distance travelled to be too large.

[Skippermark]

A couple friends have Magellans and their unit might read 6 miles into a hike but those of us with Garmins will always read higher, sometimes 2 miles more than the Magellans.