What is the most accurate GPS device?

9-29-05 | delphinium

[Delphinium]

I know this is a personal matter but I am waiting for Garmin tech support to answer. I am wanting to buy a GPS device that is accurate atleast to 2 meters.

I know there are many high tech and high intellectual folks of Freerepublic, so I decided to ask.

[TChris]

That will come as a surprise to us surveyors who have been using GPS for over 20 years with X/Y/Z accuracies of 1/4 inch.

Not with straight GPS they aren't. See a pretty detailed analysis of GPS accuracy both with and without WAAS suplemental signals here. Accuracy averaged 2-6 meters with WAAS.

[Wiz]

What are you going to do with this? Make an entry into the Grand Challenge with your UGV?

[CAWats]

Not laughing. During the CB days of the 1970's, the Realistic brand of CB was kinda decent. Of course it was no match for a Cobra, but it was good for the money.

[Redcloak]

I use mine while hunting. "CAR" is always my first waypoint. (Though I do have an eerie ability to find my way out of the boonies and right back to the point where I left the trail.)

[Wacka]

I use a GPSr (receiver) for the hobby of geocaching. It is a hobby where you use a GPSr while hiking to find containers other people have hidden. Sort of like a high tech treasure hunt.
The cheapest consumer GPSr can be found for about $90 up to $500-600. The all are reliably accurate to about 30 ft (10 meters) although they can be more accurate depending on how many satellites you can see. The differences in price are memory, maps and driving directions available for the unit.
Magellans and Garmins are the main brands, both good. Stay away from Cobras though. Third party programs are available to load coordinates from map, etc.

[rollinginmybuggy]

Coordinating my drug drops and pickups.






Kidding...

[Delphinium]

Ya gonna call in air strikes?

I was going to joke back "yes", but thought I better not kid about that kind of thing.

My husband needs one for use in mapping, helping him survey, etc.. atleast I think that is what he is doing. He has a program called earth google, and needs one compatible.

He is also an Idaho hunter.

this is the first time we have even looked into these devices.

[magellan]

"If you buy a modern GPS receiver, the accuracy will have nothing at all to do with which one you use."

This is not true with commercial GPS receivers. The more channels the receiver has, the greater the accuracy.

A Wide Area Augmentation System (WAAS) capable receiver will have better accuracy.

From Garmin (http://www.garmin.com/aboutGPS/waas.html):

"A WAAS-capable receiver can give you a position accuracy of better than three meters 95 percent of the time."

[kinsman redeemer]

It doesn't matter how much you pay for a handheld.

I have tested several handheld models and found similar solutions among all of them. All were uniformly good performers, providing results that were better than the advertised specs (typically CE of 15-m). I got between 7-9 foot(!) accuracy.

All tests were conducted under no cover and in ideal conditions (but with no WAAS!)

The study used 980 points, with 10 different recievers, including:
Trimble geoexplorer III
Garmin GPS60, eTrex, iQue3600
Lorance globalmap 100, iFinder Pro

All of these are handhelds and nothing I say is about survey-grade (second signal carrier phase, long set-ups and triangulation which can get you to sub-centimeter precision, but cost $10s of thousands) operation.

[Delphinium]

It should be a hand held, for mapping out property.

[ApplegateRanch]

Hold off. There was a thread in the last day or two about a new bird that is adding two more military, AND another civilian channel. That is supposed to allow NEW units to bring the civilian accuracy level way down, even much better than WAAS units; perhaps to a meter or less; 1 or 2 centimeters for military in motion.

You might try a search to find it. Launch; rocket; satellite; GPS all immediately come to mind to start with.

[durasell]

I have never bought a small piece of electronics from them that hasn't peformed at or above what was promised. And the stuff lasts forever.

What I do is wear a disguise -- false mustache, dark glasses, wide brimmed hat -- when going in there, so nobody will recognize me. Then, I ask the clerk to put my purchases in a plain brown paper bag, and leave through the back door.

[Delphinium]

Thanks, good advise. So you think the Garmin E trex, is as good as the 60 series as far as accuracy goes?

[Tennessee_Bob]

Going out geocaching with my daughter. It's fun, and gets us out in the woods.

[OSHA]

I follow the empty beer cans back. The faster I drink the greater the positioning accuracy.

[Delphinium]

If you want the ultimate accuracy and precision you need to go the route of base station and field station

I sure ave gotten alot of different opinions talking to different sporting goods businesses.

[Tennessee_Bob]

He is also an Idaho hunter.

And he needs a GPS for that? Heck, it's been in the same place for as long as I can remember!

[hlmencken3]

I've always wondered about this. An Alaska guide I know says even inexpensive models are accurate there within 2 meters, but he reports occaisional wide errors which he believes is the intentional 'fuzzing' of the signal for security purposes.

[Myrddin]

A WAAS enabled 12 channel GPS plus a DGPS add-on differential GPS receiver can be cobbled up for under $200 using stock Garmin parts. DGPS transmitters are commonly found near coastal waterways and rivers. Some airports and rail facilities have them as well. If you need the accuracy of differential GPS away from commercial transportation areas, you'll have a much bigger financial hit to add your own. Another poster listed the accuracy vs cost for various grades of GPS quality.

You can find free DGPS coverage at this link. Garmin claims DGPS improves accuracy to a range of 2 to 7 meters. WAAS makes a similar claim using a pair of geosynchronous satellites. The accuracy will always fall in a range because the GPS birds are always moving and your results on dependent on your relative location to the passing set of satellites.

I was just checking the GPSCity website and discovered that Garmin has discontinued the 3 models of marine DGPS receivers sold on that site.

[yarddog]

GPS models must have improved recently. Around 8 or 9 years ago, I bought a medium priced model by Garmin and was disappointed in it.

It often could not read under trees.

Recently I noticed a cheap one (Garmin etrex) on clearance at Wal-Mart. It was only $35 so I decided to give it a try with the expectation of returning it. To my surprise, it reads perfectly well indoors. Also the accuracy is very good. I don't recall exactly but I can walk out to the mail box, which is around 100 yards away and it tracks there and back right on the money.