Accuracy Etrex 20

[Mr and Mrs Boogie]

Got the Eterx 20. Loaded maps from here - http://garmin.openstreetmap.nl/. I downloaded a map for Virginia. I was able to install the map successfully, but when zoomed in, the arrow is not lining up.

 

Examples............

 

The map is zoomed out and the arrow lines up with the street

 

Then, I zoom in and the arrow isn't lined up

 

 

Another example.........

 

Lines up when zoomed out

 

Isn't lined up when zoomed in

 

Before I did anything, I left the GPS outside for about half an hour to get the satellite signals.

 

-- Sometimes it is lining up when I'm in a different area and sometimes it isn't lining up

Is this normal?

Is there something wrong with the GPS?

The actual map? Does something need to be calibrated?

In general, is there a + or - in accuracy?

Do I have to stand still for a little bit for everything to line up?

 

Just wondering because it would be a bummer when going out for a cache and everything is totally off.

 

Thanks for any replies.

 

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[+giddeanx]

Are you standing in the middle of the street? Or about 20 ft from the center? Also there is error to consider as well.

Edited June 2, 2015 by giddeanx

[+Gitchee-Gummee]

This is not unusual for a zoomed-in appearance.

 

Think of this -- the map (any map added to a GPSr) is an overlay of the coordinate grid. Overlays will rarely, if ever at all, be fully accurate.... especially when zoomed in close.

 

It appears as though you are standing still for those shots. Have you tried it all while moving towards the target?

I think you'll find that the alignment improves as you close in on the target.

 

 

EDIT to add: you should never expect absolute accuracy from a consumer-grade device... much less so, overlays to that device.

Edited June 2, 2015 by Gitchee-Gummee

[+GeoTrekker26]

I'm not sure what you are expecting "to line up" but I don't see a problem. Have you ever looked at Google maps satellite view (or Google earth) and had it overlay the map roads onto the satellite image. You will notice the calculated roads never exactly matches the real road. You will get the same variances in any map you download. Also note the road on the GPS is displayed as about 4 feet wide. Typical error on a newer GPS is +/- 15 feet in good conditions. If you give the GPS plenty of time to settle in, which means you set it down, not swing it around while holding it, you can sometimes reduce the error down to +/- 8-10 feet. However the only way you know the real error is by visiting a known accurate location.

 

Enjoy your etrex 20, it will serve you well on your caching adventures.

[+pppingme]

Most maps are not that accurate in many areas.

 

Also, road widths are typically represented too skinny on the maps.

 

That being said, the first set of pics looks dead on equal to me. Its the center of the diamond, which if you look closely on the first set, is "off road" in both cases.

[Mr and Mrs Boogie]

You all have been a very big help. BIG thanks!