GPS accuracy

Flatrock · Jul 25, 2011

I was just wondering if any of you guys have had issues with the accuracy of your GPS, particularly the Garmin Dakota 20? I picked one up on a good sale but it doesnt seem to be working quite right. I live about 100 yards north of a main road and on my GPS, it shows be being about 10 yards to the south of that road. When I look at the satellite status,it will have 7-9 satellites in view and says my accuracy is within 25 feet, yet on the map still showing me 100 yards off. I emailed Garmin and they had me do a software update and a complete reset but that didn't work. Then they told me that accuracy can be plus or minus a quarter mile. I will be using the GPS this fall to determine public/private land and need to be confident that I am exactly where I am supposed to be.
Anybody have any similar experience or recommendations?

WT_in_MT · Jul 25, 2011

Here is a link to a thread in which I show examples like you're seeing. http://onyourownadventures.com/hunttalk/showthread.php?p=2126558#post2126558

The display issue you're seeing is most likely an inaccuracy in your base map not your GPSr. Whatever you're planning to use for a public land map on your GPSr may be more or less accurate than the map you have now. The only way to be confident in it is lots of ground proofing, preferably over survey markers.

BuzzH · Jul 25, 2011

WT_in_MT has it right....its more than likely your base maps.

I have some free maps downloaded on my GPS and they are not real good, routinely off by 100-300 feet.

An example is when I'm driving down the interstate, the free maps have me off the interstate by 150+ feet. Another example is on most every 2-track road I'm off at least that much as well.

A few weeks ago I got the base maps from huntinggpsmaps.com and they are incredibly accurate. Not only do I track right on the interstate, but when I zoom in, it shows that I am on the correct SIDE of the interstate. I'll be using a gps tomorrow to locate some section corners and I've no doubt the accuracy on the base map will be right on.

I'd say its your base maps for sure though...

pointingdogsrule · Jul 25, 2011

I use my GPS for geo-caching and it usually gets me into a few feet of the location.

good luck to all
the dog

Flatrock · Jul 25, 2011

Thanks guys. Yea I'm thinking it is most likely my base map. I went for a drive on the highway and initially it showed me about 300 feet east of the highway. As I drove though, my track would go back and forth across the highway as the road turned. Then when I drove back, my new track paralleled my first track perfectly, even showing a 20 foot difference because of driving in the other lane, just like Buzz said.
Buzz, thanks too for mentioning huntinggpsmaps, I was curious if the accuracy would be better with that chip. I will be buying the Wyoming one shortly.

Topgun 30-06 · Jul 25, 2011

Yep, I'm also sure that's what it is and I can't believe anyone from Garmin above the janitor level would tell you their device could be off like you mentioned. That person should not be working with the public, LOL!

Flatrock · Jul 26, 2011

Topgun 30-06 said:
Yep, I'm also sure that's what it is and I can't believe anyone from Garmin above the janitor level would tell you their device could be off like you mentioned. That person should not be working with the public, LOL!

Here is the actual email that I got...

"When using a recreational GPS device the current position displayed on
the screen may at times be slightly inaccurate.

The preloaded basemap in the GPS devices has been drawn from a map with
a scale of 1:100,000. A level of accuracy of .25 miles (1,320 feet) can
be expected from a map of this scale.

Using a detailed mapping program, such as MapSource City Navigator NT,
will increase the accuracy of the current position. This program has an
approximate accuracy of 40 feet, so the accuracy ring around your actual
position will be smaller, assuming that the GPS receiver has a good lock
on the satellites.

Please respond to this email if further assistance is needed."

So I guess that means that when I look at the satellite coverage on my unit and it says it is accurate to 25 feet, that is probably correct in regards to my actual position. Garmin is just saying that as far as displaying my location on the screen, it could be up to 1/4 mile off?

mtmiller · Jul 26, 2011

BuzzH said:
I'll be using a gps tomorrow to locate some section corners and I've no doubt the accuracy on the base map will be right on.

I get about 12 - 15 from surveyed sections with a Garmin and huntinggpsmaps

Topgun 30-06 · Jul 27, 2011

vdo84---I think I understand what you are saying and if that's the case, what the heck good is the map?

Goldtip · Jul 27, 2011

Has anyone used the huntinggpsmaps on the Garmin Rino's? Was looking at their website, and the chip is definitely compatible, but was wondering if with the PLAT maps and the small screen of my Rino 530HCx, that maybe with landowners names on the map if it would be too cluttered? Anyone have any input in this regard?

IrishRover · Jul 28, 2011

I think you'll probably be OK. I believe the gpshuntingmaps will show ownership down to 40 acres maybe, so if you zoom in really tight you will likely not see ownership names at all or may
have to pan around to find the owners name

GPS accuracy

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