Accuracies

February 2, 2004

I have noticed while reading through posts that many people think that 50' accuracy is normal, and even acceptable. Is this the case? Now, I'm talking NON-WAAS. I've been using a borrowed Magellan 4000 XL (12-15yrs old, non WAAS), and I've gotten within 10' of all five caches I've looked for.

Are these 50' inaccuracies due to dense tree cover, or what? I've gotten within 10' even under tall pines.

What gives?

I've been considering getting a fancy new GPS (Meridian Platinum), but if it won't get me any closer, why should I bother?

9.4k · February 2, 2004

I've had as good as 7 feet, but usually it's in the 15-22 foot range.

February 2, 2004

I typically get 15-20 with my Legend. I had 15 under a cement bridge on a micro i was looking for today.

2k · February 2, 2004

My Legand and my Platinium would place me within 2 or 3 feet of a cache that posted accurate coordinates. I think the Platy is a nicer unit, at twice the price it should be. But vaeraging is what makes the difference.

I've been kind of wondering about the 50 thing myself. Round my parts a cache that is that far away from the posted coord's gets a lot of notes in the log. And usually corrected coordinates. But tree cover isn't as much of a problem here.

February 2, 2004

It's bound to be cover of some sort, or incorrect holding of the unit. I've not paid much attention, but I see that some units get better reception depending on the angle you hold them.

February 2, 2004

IMHO - There are, I believe, too many variables to determine why coordinates for a given hide does not agree from one GPS to another. Cockpit trouble (user inexperience with the GPS) on either end (hider or seeker) often make a significant difference. Natural and man-made obstacles, weather, and other factors may also play a part. Once you get some experience within a group of folks who create caches in your area, you'll identify those who produce accurate coordinates for their work and those who either don't fully understand how to use their equipment or who just "hide and run" without taking the time to verify coordinates. When you have trouble nailing down the cache, your GPSr should probably be the last element upon which to place the blame.

3.1k · February 2, 2004

sometimes mine says 0 feet to cache, sometimes it's 20 feet. lots of variables and it's nothing to worry about

24.7k · February 2, 2004

15-20 is normal for me.

February 2, 2004

It's bound to be cover of some sort, or incorrect holding of the unit. I've not paid much attention, but I see that some units get better reception depending on the angle you hold them.

I am sure I need help in this area then. What is the correct way to hold a GPS? I have tried over my head, way out in front, to the side.....

February 2, 2004

What is the correct way to hold a GPS? I have tried over my head, way out in front, to the side.....

Holding it over your head makes it difficult to read...

4k · February 2, 2004

I will typically get a "reading" of 12 to 15 feet without WAAS on my Legend, and on many caches the GPSr led me right to it. One I did a couple of weeks ago under tree cover led me to actually stand right on top of the cache! Friday, when I hid my second cache, I was under trees on a cold, cloudy day, and had an accuracy reading of 8 feet. I never use WAAS.

4k · February 2, 2004

It's bound to be cover of some sort, or incorrect holding of the unit. I've not paid much attention, but I see that some units get better reception depending on the angle you hold them.

I am sure I need help in this area then. What is the correct way to hold a GPS? I have tried over my head, way out in front, to the side.....

I don't know about other brands, but most of the Garmin handhelds need to be held either parallel to the ground (flat) or perpindicular (straight up) to get a valid reading. Holding it right next to your body or out to arm's length doesn't seem to make much difference, at least from what I've seen with my Legend.

38.2k · February 2, 2004

I don't know about other brands, but most of the Garmin handhelds need to be held either parallel to the ground (flat) or perpindicular (straight up) to get a valid reading. Holding it right next to your body or out to arm's length doesn't seem to make much difference, at least from what I've seen with my Legend.

This is true only for the Garmins with the patch antenna (eTrex line and the Geckos). The other Garmins work fine in any position.

As far as accuracy, I've zeroed out my indicator on a cache, and found many 50 or more feet away, but most seem to be 15-30 feet away.

The 50 foot number is usually a worst case. Since my unit will usually have an EPE of 20- 25 feet and the person who placed the cache likely had a similar EPE, the possibility exists that you will be 40-50 feet off even under the best conditions.

February 2, 2004

... I never use WAAS.

Isn't that risky; or even dangerous?

4k · February 2, 2004

... I never use WAAS.

Isn't that risky; or even dangerous?

I like livin' on the edge!

4.8k · February 2, 2004

I would say the average for me is around 10-15 on my 315.

February 2, 2004

For the past few days my son and I have been taking readings from a yellow eTrex (no WAAS) and a Vista (WAAS enabled). They are positioned so that WAAS reception will not be a problem.

So far we have 16 pairs of readings over three days at various times. The two receivers have not been more than 3 meters different in either easting or northing (we're using UTM to keep the math simple), and that extreme has only happened twice so far. Usually they seem to be within 2 meters of each other.

I'm finding this kind of suprising. That yellow eTrex seems to be performing pretty dang well for being older and not having WAAS. Just looking at the raw data, WAAS only seems more "confident" as far as the positioning goes, usually being about half that of the non-WAAS unit.

George

February 2, 2004

I find this very interesting, as I recently hid a multi cache where you need to project waypoints to move from stage to stage. I ran the course several times before activating the cache, using both a Vista and a yellow etrex, and I was getting what I considered a wide variation in results, between 7 and 80 feet on different days, with more consistent variation at some stages than others. Now the big problem here is that you have double the error since you are setting both the starting point and the ending point using 2 different GPSrs, and the logs so far have shown the coordinates to be outside my "comfortable" error range of 30 feet, although everyone's been able to find the cache. I averaged the coords from all my runs, but since I had so much variation I suspect a few outlier points skewed the final coords. I've asked recent finders to send my their waypoints, and I plan to fine tune the cache this week. But to stay on the point, I figure if it's within 25-30 feet I've got no complaints. 50' is unusually far off, although if that is accompanied by a lot of "jumpiness" in the distance then you're just in a bad reception area, possibly near some sort of reflecting surface. I hunted a cache in the middle of a large lake, clear blue sky above me, and couldn't get the GPS to settle within 100' of the cache. One side of the lake was bordered by a sheer rock wall several hundred feet high, and the GPS signals were likely bouncing off it and giving my Vista fits.

February 2, 2004

10 to 15 feet for me.

February 2, 2004

My Garmin legend gets me within 10-15 feet normally. A few times I have had it be 5 feet or even 0.

4k · February 3, 2004

For the past few days my son and I have been taking readings from a yellow eTrex (no WAAS) and a Vista (WAAS enabled). They are positioned so that WAAS reception will not be a problem.

So far we have 16 pairs of readings over three days at various times. The two receivers have not been more than 3 meters different in either easting or northing (we're using UTM to keep the math simple), and that extreme has only happened twice so far. Usually they seem to be within 2 meters of each other.

I'm finding this kind of suprising. That yellow eTrex seems to be performing pretty dang well for being older and not having WAAS. Just looking at the raw data, WAAS only seems more "confident" as far as the positioning goes, usually being about half that of the non-WAAS unit.

George

Just curious, how far apart were the two units when you were doing the comparison? I know I read here in the forums that two units held within 3 feet of each other will cause disturbances in the signal (possibly from Kerry or Eraseek?). As for me, I'm still a firm believer in non-WAAS from my own experiments and observations. Even so, a lot of times, my Legend will lead me to within a foot or so of the cache, even under tree cover on cloudy days.

February 3, 2004

Just curious, how far apart were the two units when you were doing the comparison? I know I read here in the forums that two units held within 3 feet of each other will cause disturbances in the signal (possibly from Kerry or Eraseek?). As for me, I'm still a firm believer in non-WAAS from my own experiments and observations. Even so, a lot of times, my Legend will lead me to within a foot or so of the cache, even under tree cover on cloudy days.

I thought about that. I spaced them consistantly about a foot apart. Hopefully that will quell any interference problem, but maybe not.

I guess a question would be how such interference would tend to manifest itself. My biggest suprise is that the non-WAAS unit seems a lot more accurate than I would have suspected. Maybe it's peaking over at the Vista and cheating?

It's not that I think WAAS is performing poorly, I'm just amazed on how non-WAAS seems to be performing so well.

George

4k · February 3, 2004

It's not that I think WAAS is performing poorly, I'm just amazed on how non-WAAS seems to be performing so well.

That was my finding too.....for all the trouble and delicacy of WAAS acquisition, non-WAAS wasn't different enough (and occasionally better) to warrant using WAAS at all for me.

9.4k · February 3, 2004

It's not that I think WAAS is performing poorly, I'm just amazed on how non-WAAS seems to be performing so well.

That was my finding too.....for all the trouble and delicacy of WAAS acquisition, non-WAAS wasn't different enough (and occasionally better) to warrant using WAAS at all for me.

Besides, it wastes batteries

4k · February 3, 2004

It's not that I think WAAS is performing poorly, I'm just amazed on how non-WAAS seems to be performing so well.

That was my finding too.....for all the trouble and delicacy of WAAS acquisition, non-WAAS wasn't different enough (and occasionally better) to warrant using WAAS at all for me.

Besides, it wastes batteries

And some people waste my oxygen......

February 3, 2004

On my SporTrak Map, I tend to end up 10 to 15 feet away from the cache. I tend to not trust the receiver as much as I should. I start looking when I'm about 50 feet out.

Is WAAS the reason that my unit is going thru the batteries so fast? I put a new set in 2 days ago and have used the unit for about 3 hours and the battery indicator shows about half power.

F_M

4k · February 3, 2004

On my SporTrak Map, I tend to end up 10 to 15 feet away from the cache. I tend to not trust the receiver as much as I should. I start looking when I'm about 50 feet out.

Is WAAS the reason that my unit is going thru the batteries so fast? I put a new set in 2 days ago and have used the unit for about 3 hours and the battery indicator shows about half power.

F_M

Quite possibly....3 hours to half power isn't very good at all. I don't use WAAS (have I mentioned that yet?) and get anywhere from 20 to 30 hours from my ecokilling Ray-O-Vacs in my Legend.

February 3, 2004

I might be off on the numbers. It could have also been a pack of batteries that my son put in the drawer. Who knows. I'll have to keep an eye on this.

I did have it in the car a lot lately. Does taking the temperature from 70° to 30° and back to 70° kill batteries?

F_M

4.4k · February 3, 2004

Click Battery Saver Mode.

February 3, 2004

Click Battery Saver Mode.

Will that hamper my caching at all? Will the reception be affected?

F_M

4.4k · February 3, 2004

???????????????????/ dunno

I usually do not worry about batteries,I keep my unit powered in the truck till I get ready to go out,then it doesn't take long and I hook it back up to external power.

I am picky I use Duracell Ultra's,and they last me for a week at least when I am working on the Secondary control benchmarks in the quadrangle as well as the Houses for the fire maps.

I have had reasonable useage on batteries.

but I read it does reduce the rate of satellite signal updating

Accuracies

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