Fieldcraft GPS and false readings

[lachoneus]

A few years ago, my sons and I were hunting in the Kaibab area of Arizona. We had with us a new GPS unit, a Garmin E-trex Legend HCX. It seemed to be working normally. Finding a location that seemed promising for deer, I paused to input a waypoint. That's when I noticed that the map screen suddenly seemed unusual -- it did not match the surrounding area. I zoomed out, and found to my surprise that it indicated that our current location was about 350 miles east in New Mexico. I thought I must be reading something wrong, so I had my sons confirm what I saw on the screen. I turned the unit off, then turned it back on, and the screen map again correctly showed our position in Arizona.

Being old, I have always harbored a bit of mistrust toward GPS units, and this experience, while it caused me no real problem, did nothing to increase my confidence level.

I was wondering, though, if any others have experienced similar false readings with GPS units, or if my experience was just a one-off anomaly?

 

[kraigWY]

Re: GPS and false readings

I have an Garmin Etrex vista.

It's pretty good. I've found errors were cause by operator headspace.

I have had problems with other GPS's in the past. For unknown reason loosing all my Waypoints, only to have them show up again sometime later. Had a Garmon just quit on me.

A couple times in the Big Horns on a claar cool night I coudn't gind any satalites what so ever.

They are fun to play with but I wouldnt' trust my life with one. Just don't have the confidence in them. A good 1:24000 map and compass has never let me down.

I'll take both, GPS and Map anywhere I go.

Sitll they are fun to play with. I have a mem chip for my Etrex that shows Private and public lands. Even list the land owner's name. That's handy if I want to know who own's what.

 

[Willyz_54]

Re: GPS and false readings

Worst GPS issue I have had was with and old Magellan Explorist. The unit went brain dead on me on a hike in the San Francisco Peaks. It would boot up, backlight, but the screen was blank. Had a map and compass too so it was moderately frustrating versus being a deal breaker for the trip.

 

[3oh8er]

Re: GPS and false readings

Even the best GPS can go haywire at random times. They need five satellites for a fix and if one drops out or a sufficiently strong RF signal interferes your out of touch. Best to keep the map and compass handy.

 

[kraigWY]

Re: GPS and false readings

One needs to really understand GPS's and Accuracy.

To be accurate you need to move. If you're standing still, only you are standing still, everything else is moving. You have to move for the GPS to constantly calculate its readings.

A GPS with WAAS (Wide Area Augmentation System) is going to be more accurate then one without WAAS.

An example without WAAS your accuracy should be within 49.2 feet horizonial and 62.3 ft. verticle.

With WAAS it would be 9.8 ft horizontal accuracy and 19.7 feet Vertical accuracy.

FAA says accuracy using WAAS is 23 Feet. GPS manufacturers claim accuracy is 9.8 ft.

This is accuracy over a period of time. WAAS makes a reciever accurate to 9.8 Ft 95% of the time and 23 ft the remaining 5%.

Meaning if you go to the same spot 100 times. 95 times you will be within 9.8 feet. the other 5 times you will be within 23 feet.

Basicly you have to know your GPS and you have to know how to use it.

I've had GPS's crater, but normally its because of batteries or twice, I've had GPSs just crater. They had to be sent back to the factory.

As I've mentioned in other post, I really like GPS', they are fun to play with and they have many uses besides what most people think.

But as you mentioned, I'd never carry a GPS without a map and compass. Espeically if my life was at stake. I've never had a map and compass let me down.

But that doesn't mean I'm going to give up my GPS. When I teach map reading or orientation classes I teach both and the benifits of using them together.

Having said all that, the in-accuracy I've found with GPSs (excluding batteries going south and the GPS being or getting broke) is operator error.

Most people don't set them up right before using them. The same can be said about maps, they are only as accurate as the people using them.

An example, how many people do you see that know how to set up a USGS map to use MGRS (Military Grid Reference System, and then set their GPS to MGRS instead of Latitude/Longitude?

You'd be supprised how many people don't really know how to use a compass. Yet they'll blame the compass and map if they end up in the wrong county.

 

[Killer Spade 13]

Re: GPS and false readings

Regardless, wish the hell we'd had them in Viet Nam!!!

 

[ITyson]

Re: GPS and false readings

I was shed hunting a couple months ago and had a new garmin crash out on me. I was walking with the sun at my back for about 2 hours and wanted to go back to the truck, hit the waypoint and it was sending me south instead of west like it should. I ending up at the truck and it said I needed to go 2 more miles south to arrive at my way point I makes the truck for. I marked camp then 2 days later wile setting at the road about a mile away clicked my waypoint for camp and it said 9 more miles in the wrong direction.

I reset the thing and changed battery's, I won't be using it to hunt this year.

 

[kraigWY]

Re: GPS and false readings

When setting waypoints you have to be careful where the little black diamond pointer is.

I set up a target and (thought) I marked it as a way point to practice with my Mil reading.

When I got set up something didn't look right when I looked through the scope. I firgured I was way off on my mil reading, started shooting and my data book recordings for come ups matched my Mil readings but was no where close to the GPS. My map also said my GPS waypoint was wrong.

Turns out I screwed up and marked my target about 300 yards the other way.

Couldn't blame the GPS, this was strickly operatoer headspace.

I like GPS's but I wouldn't go some where serious without a map. When I mark a waypoint I also plot it on the map.

I have a longitude/latitude ruler for the scale of map I'm using that way I can use lonitude/latitude with or without a GPS.

 

[lachoneus]

Re: GPS and false readings

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ITyson</div><div class="ubbcode-body">I was walking with the sun at my back for about 2 hours and wanted to go back to the truck, hit the waypoint and it was sending me south instead of west like it should. I ending up at the truck and it said I needed to go 2 more miles south to arrive at my way point I makes the truck for. </div></div>

I haven't experienced that great of an error in getting to a waypoint, but a couple of years ago I was canoeing in Canada. I set a waypoint at our point of departure as we left on a long loop trip across several lakes. About 10 days later on our return, I turned on the GPS and plotted the route to the waypoint, and then followed the GPS direction indicator as we crossed a large lake to the takeout. As we got to within about a mile of the takeout, we could see it fairly well, but the GPS indicated that we should be heading to a point about 600 yards to the south. I continued to watch the direction indicator as we approached the takeout. It continued to indicate a location about 600 yards south until we were just a few yards short of the takeout. Had we been paddling in fog, we would have initially missed the takeout by a fair distance.

Reminded me of that old Groucho Marx line: "Who are you going to believe, me or your lying eyes?"

 

[2Shots]

Re: GPS and false readings

So does anybody know of a reliable unit they have had no trouble from? I have an older unit I bought 15 years ago that I would like to upgrade because it takes like 4 AA batteries and will hardly last 10 hours, it gets kind of squirrely with canopy overhead and has a hard time with walking speeds and direction sometime. Please let me know if there are good ones out there.

 

[Killer Spade 13]

Re: GPS and false readings

Got a Garmin 76 something or other. It's pretty damned good. Kinda old, but good.

 

[kraigWY]

Re: GPS and false readings

The best I've used (and have) is the Garmin Etrex Vista.