Accuracy of 12 Channel Units - GPS Choice Question

[+creagerstonefamily]

Hi everyone,

 

ACCURACY

Since all of the caches are listed with positions in the thousandths of a minute, I'm a bit confused.

 

Are the newer models of GPS accurate to thousandths of a minute or is the extra digit added by the website mapping software?

 

GPS CHOICE

I have a practically mint condition Magellan Pioneer GPS (with box, dox, wriststrap) that I bought about five years ago. It will only go down to hundredths of a minute. We're going to get a new GPS since we all enjoyed Geocaching so much.

 

I'm leaning towards the eTrex Legend instead of the SporTrak Map for the following reasons:

 

- the $50 rebate brings the overall price down to $165

- it includes PC link cable

- I'm a little ticked at Magellan for leading me to think the Pioneer was a 12 channel receiver with the "AllView 12" designation

- better resolution (but smaller screen size)

 

Any non-flame war thoughts on the above?

 

Thanks!

 

Jason

[Rubbertoe]

Well, depending on how hooked you plan on getting - the Legend might not have enough bells and whistles for you in the long run.

 

I started out with a plain ol' yellow eTrex, and quickly moved on up - I'ev been using a Vista for about a year now, and I can't imagine using anything less. At first I thought having extra memory and a compass and 24 megs for maps was all overkill - but now I've been spoiled and can't do without 'em.

 

Click the Toe - and please stop confusing your opinion with fact, ok?

[Rubbertoe]

Well, depending on how hooked you plan on getting - the Legend might not have enough bells and whistles for you in the long run.

 

I started out with a plain ol' yellow eTrex, and quickly moved on up - I'ev been using a Vista for about a year now, and I can't imagine using anything less. At first I thought having extra memory and a compass and 24 megs for maps was all overkill - but now I've been spoiled and can't do without 'em.

 

Click the Toe - and please stop confusing your opinion with fact, ok?

[+mrp]

quote:

---

Originally posted by CreagerStone Family:

ACCURACY

Since all of the caches are listed with positions in the thousandths of a minute, I'm a bit confused.

 

Are the newer models of GPS accurate to thousandths of a minute or is the extra digit added by the website mapping software?

---

 

This a perfect example of the difference between accuracy and precision. The precision (in the coordinate format) is 1/1000th of an arcminute of latittude or longitude. This comes out to about 6 ft N/S and 4 ft E/W for most latitudes in Europe and North America. Now your typical GPSr isn't quite that accurate. It's usually accurate to within 20 or 30 ft since SA has been turned off, but if your unit only displays 1/100th of an arcminute, then the precision is 40-60ft, and it can't express the location to the proper level of precision.

 

Some people argue that we should use the coordinate format of decimal degrees to the 1/100,000th of a degree (40.49341 degrees as opposed to 40d 29.605') because the precision is 2-3 ft as opposed to 4-6 ft. with decimal minutes. But this misses the fact the accuracy of the GPS receiver is still (at best) only 15-20 ft, and expressing greater precision doesn't change that. Similar arguments can be made for the UTM coordinate format, but have the same problems.

 

Older receivers only display 1/100th of a minute becuase before SA was discontinued, the accuracy of the GPSr was only good to within 200-300ft, and entering (or producing) coordinates more precise than that didn't make sense. AFAIK, The only receiver still on the market that has this limitation is the Magellan 310. You see them for sale at dirt cheap prices occaionally ($60 or so), but they're not useful for geocaching.

 

(Selective Availability refers to the practice of scrambling the timing signals slightly for non-military receivers so that the accuracy was degraded. However, by May 2000 there were enough workarounds to get better accuracy anyway that the military disconintued the practice. Now they have a system that called something like "selective deniability" and allows them to blank the system for certain geographic regions. Though my understanding if spotty and I could have this wrong.)

 

-- Mitch

[+creagerstonefamily]

Thanks, Mitch!

 

That makes perfect sense. I was trying to figure out how to phrase a question about significant digits, but it's been too long since college and too long since I had a good night's sleep. :-)

 

I remember being excited when President Clinton signed the bill that banished selective availabilty.

 

Since I found the link for shopharmony.com, I'm now leaning towards the Meridian Platinum for $249. I think this is definitely a case of "a little more now for a lot less later".

[+RobAGD]

Well if you really like Geocaching, and depending on the area you live in, you may want to look at something a little better than teh eTrex line. They tend to preform poorly in heavy tree cover. You might want to look for a Garmin 3+ while a bit more expensive you will have great coverage even in heavy tree cover. Or maybe look into the 76 line as I belive they also have the better antenna.( I am waiting for the 72 pricing as I am looking at GPSr's for presents for Xmass for friends )

 

Ask around your local area and maybe got out with some people and get a feel for the units the use.

 

-Robert

[+TeamJiffy]

...I keep on reading on how horrible the eTrex line is under heavy tree cover. I've done over 40 caches with my wife, using both a GPS-V and a Vista (we are GPSr hogs - just like we are remote control hogs) - and I have to say that the tree coverage with the GPS V is only marginally better than the Vista.

 

I think the GPS V is either over-rated with coverage, or the Vista is under-rated. We've done over 40 cache hunts with both, and there is a SMALL degree of tree density (a small small small one) where the GPS V gets a lock, and the Vista doesn't. Go outside of that narrow range, and you lose coverage with my GPS V as well.

[+RobAGD]

Well there was a much bigger differnace between my vriefs eTrex Vista and my 3+ and that seems to follow teh trend I have seen on the fourms.

 

Thats the major reason I havent really looked hard at the eTrex line for my friends.

 

But to each there own I guess, maybe you got luck on the eTrex and unlucky on the V.

 

-Robert

[+apersson850]

There seems to be a big difference between different Vistas. Some friends and I bought four at the same time, to get a better deal, and it seems that some of them are better than the other. Or is it the user holding them differently. That makes a BIG difference too.

 

Anders

[+SecretSpy]

I guess if I was looking for a cache in say a underground drain pipe I might lose sat signal with my Vista. This tree cover thing is really silly. You're cache hunting folks. It still involves a bit of brain work once you get within 30 ft. I guess these Vista critics want there GPSr to take them within inches of the cache. Get real. The Vista is an awesome device in a very small package. In tree cover mine works great. You hold it flat folks and let it set for half a minute take a bearing with the Mag Compass and you walk right up to the cache. What's the big deal. If you want to find caches in houses or underground buy a TRIMBLE.

 

LowlyWorm Says Gig 'em Aggies

[Kerry.]

quote:

---

Originally posted by SecretSpy & LowlyWorm:

... If you want to find caches in houses or underground buy a TRIMBLE.

---

 

Your kidding

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by SecretSpy & LowlyWorm:

... If you want to find caches in houses or underground buy a TRIMBLE.

---

 

Your kidding

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by CreagerStone Family:

 

I'm leaning towards the eTrex Legend instead of the SporTrak Map for the following reasons:

 

.....

.....

- I'm a little ticked at Magellan for leading me to think the Pioneer was a 12 channel receiver with the "AllView 12" designation

.....

---

 

What has the specifications of a 5 year old receiver got to do with this decision. Getting away from the 12 channel myth for a moment that's the way things (generally) were "back then" and there were other instances of that similar ploy with different manufacturers.

 

The 12 channel myth do you really think 12 channel receivers are more accurate simply because that are 12 channel

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[Kerry.]

quote:

---

Originally posted by CreagerStone Family:

 

I'm leaning towards the eTrex Legend instead of the SporTrak Map for the following reasons:

 

.....

.....

- I'm a little ticked at Magellan for leading me to think the Pioneer was a 12 channel receiver with the "AllView 12" designation

.....

---

 

What has the specifications of a 5 year old receiver got to do with this decision. Getting away from the 12 channel myth for a moment that's the way things (generally) were "back then" and there were other instances of that similar ploy with different manufacturers.

 

The 12 channel myth do you really think 12 channel receivers are more accurate simply because that are 12 channel

 

Cheers, Kerry.

 

I never get lost everybody keeps telling me where to go

[+creagerstonefamily]

quote:

---

What has the specifications of a 5 year old receiver got to do with this decision.

---

 

I currently own a Pioneer which I just recently discovered was a 2 channel receiver. I don't like it when companies play games like the "AllView 12" designation. That led me to think that it was a 12 channel receiver.

 

I hold grudges against companies that do things like that. One company that will never see a dime of my money (or my friends' monies, if I can help it) is TeamGPS.com because they lie on their website. They claim they will beat any authorized dealer's price on any in stock item.

 

When push came to shove, they refused to do it (but that's another thread).

 

It's a moot point now, though, since a Meridian Platinum is working its way to me via UPS. I like the idea of "unlock codes" even less than the "AllView12". Plus, since the Meridian uses SD flash cards, I can actually use it on cross country trips since we don't have a laptop to upload new maps.