Waas In Hawaii

[Samalolo]

I have a Garmin etrex Legend .. does anyone know if enabling the WAAS feature will help me any in Hawaii?

 

Aloha

Sam

[+Thot]

There are WAAS ground stations in Hawaii, so WAAS correction signals are provided.

[tossedsalad]

From what I have read, there are two WAAS satellites, one over the Atlantic and one over the Pacific. They are geosynchronous, so they are very high up, but over the equator. So in much of the US they are often blocked by terrain. But in Hawaii the one should be nearly overhead so that you will be able to "see" it much more than we do.

[+Kai Team]

We geocached in Hawaii last June and were able to use WAAS on our eTrex Vista. You shouldn't have a problem.

 

Edit: Typo

Edited June 9, 2005 by Kai Team

[Samalolo]

Very cool, glad to hear that. I have it enabled now :-)

 

Aloha,

Sam

[+sbell111]

You might consider two things before you decide to leave it on.

 

First, WAAS is not going to help you much.

 

Second, I'm told that the unit will chew up batteries quicker with WAAS on.

[+Team Cotati]

You might consider two things before you decide to leave it on.

 

First, WAAS is not going to help you much.

 

Second, I'm told that the unit will chew up batteries quicker with WAAS on.

Excuse me: "You've heard the term WAAS, seen it on packaging and ads for Garmin® products, and maybe even know it stands for Wide Area Augmentation System. Okay, so what the heck is it? Basically, it's a system of satellites and ground stations that provide GPS signal corrections, giving you even better position accuracy. How much better? Try an average of up to five times better. A WAAS-capable receiver can give you a position accuracy of better than three meters 95 percent of the time. And you don't have to purchase additional receiving equipment or pay service fees to utilize WAAS."

 

Pronouncements..........gotta love 'em.

Edited June 10, 2005 by Team cotati697

[+Greymane]

Ok, if it is so gosh darn awesome, why doesn't it have a better name like ....

 

GOLIATH?

 

Guardian Of Lost Idiots And Terrified Hikers

 

What kind of name is WAAS?

[+Jeep_Dog]

You might consider two things before you decide to leave it on.

 

First, WAAS is not going to help you much.

 

Second, I'm told that the unit will chew up batteries quicker with WAAS on.

I have seen accuracy improve in excess of 5 feet when enabling WAAS (yes, sometimes I get bored out there on the trail and start fiddling with my GPSr, like turn WAAS on and off).

 

There was an older thread covering accuracy, battery life, and speed survey on GPSr units with WAAS on/off. This thread was quite informative, and worthy of reading. The survey really revealed that around half the folks found it drained batteries, the other found it did not... also depending on types of batteries used. Even those that found some degredation on battery life reported it was hardly noticeable...

[+souperteam]

We had it enabled on our GPS when we were on Kauai last month. I think it led to our being off course a few times because the hiders probably didn't have it on. I've noticed on the one log page that most people are saying that their GPS pointed them in the wrong direction. Hmmmmmm

[+Kai Team]

You might consider two things before you decide to leave it on.

 

First, WAAS is not going to help you much.

 

Second, I'm told that the unit will chew up batteries quicker with WAAS on.

First, WAAS improves accuracy considerably. I routinely get EPE (accuracy) of less than 10 feet with WAAS turned on.

 

Second, the additional drain on batteries is minimal, and the battery time lost is more than made up for by the battery time saved not wandering around in the wrong place! Plus it's easy to carry spare batteries (I recommend NiMH rechargables, which are much more cost effective over the long run).

 

Trust me, you want to use WAAS in Hawaii - it's so beautiful and there's so much to see that you don't want to spend too much time with your head down, poking around for the cache. And some of those caches are hidden in old lava fields (read: "very sharp rocks") - the increased accuracy makes your caching experience much more enjoyable!

Edited June 10, 2005 by Kai Team

[+Kai Team]

We had it enabled on our GPS when we were on Kauai last month.  I think it led to our being off course a few times because the hiders probably didn't have it on.  I've noticed on the one log page that most people are saying that their GPS pointed them in the wrong direction.  Hmmmmmm

Sorry, but increased accuracy cannot lead to decreased accuracy.

 

If someone places a cache with an EPE (estimated positional error) of 60 feet on their GPSr, then the cache is (theoretically) somewhere within a 60 foot radius of the waypoint they marked.

 

If you go seeking it with an EPE of 60 feet on your GPSr, then their waypoint (not the cache) is somewhere within a 60 feet radius of where you're standing. The combined error could be as much as 120 feet (the wapoint the hider recorded was 60 feet off from the true coordinates of the cache, and you're 60 feet off from the waypoint the hider recorded).

 

On the other hand, if you go in with WAAS enabled and a EPE of 7 feet on your GPSr, the combined error is no more than 67 feet (the hider's 60 foot error from the cache and your 7 foot error from the hider's waypoint).

 

Increased accuracy on your GPSr (i.e. WAAS) cannot make up for the error in the hider's waypoint, but it also cannot put you further off course, no matter how high the hider's error was. Increased accuracy leads to being closer in every case, not further away!

[+sbell111]

My understanding is that the majority of the benefits are in computing your elevation, not lat/long.

 

I would call an improvement in EPE of 5% to be minimal.

Edited June 10, 2005 by sbell111

[+Kai Team]

My understanding is that the majority of the benefits are in computing your elevation, not lat/long. 

 

I would call an improvement in EPE of 5% to be minimal.

Sorry to be so blunt, but your understanding is flat out wrong. You don't have to take my word for it - facts about WAAS, how it works, and what it does are widely available from many credible sources on the Internet. Just do a Google search on "WAAS".

 

To address the misinformation posted here so that others aren't mislead:

 

1) WAAS corrects for GPS signal errors caused by ionospheric disturbances, timing, and satellite orbit errors, and it provides vital integrity information regarding the health of each GPS satellite. Accuracy improves in all dimensions (altitude, lat, lon), because the calculated position from your GPS receiver to each navigation satellite you can receive is more accurate.

 

This misconception probably comes from the fact that WAAS was developed in collaboration with the FAA to help guide precision aircraft landings, but that does not mean it only improves the accuracy of elevation.

 

2) I don't know where "5%" came from - from 15 meters to less than 3 meters is an 80% plus improvement in EPE, hardly "minimal".

 

The OP asked about WAAS reception in Hawaii - I've used WAAS on three islands (Kauai, Maui, and Hawaii) - reception is avaialble (unless you're standing in a place that obstructs the view of the satellite), and it reduces EPE considerably. 'Nough said.

[+sbell111]

Sorry to be so blunt, ...

1. Your first point depends totally on the assumptions in your second.

 

2. Per Garmin, WAAS capable receivers typically have accuracies of 3-5 meters horizontally and 3-7 meters in altitude. My old, trusty GPS 3+ routinely was accurate to 12-15 feet. I don't feel like doing the metric conversion, but it doesn't appear that WAAS gives you an 80% improvement, does it?

 

BTW, who's non-WAAS GPSr is only accurate to 15 meters? Isn't that around 50 feet?

 

'Nough said.

Edited June 10, 2005 by sbell111

[+Thot]

BTW, who's non-WAAS GPSr is only accurate to 15 meters?  Isn't that around 50 feet? 

 

'Nough said.

Fifteen meters is the advertised accuracy for units without WAAS correction. And yes, that's about 50 feet.

 

One example the Magellan GPS 315

Edited June 11, 2005 by Thot

[Samalolo]

Do you guys usually take a reading with your GPS right at the cache location then compare it to the published coordinates?

It would be interesting to have a cache that required everyone to post their coords and we could all compare how far off our units are.

 

Aloha,

Sam

[+Thot]

It would be interesting to have a cache that required everyone to post their coords and we could all compare how far off our units are.

Clever idea. I'll add that to my next cache.

[+CYBret]

It would be interesting to have a cache that required everyone to post their coords and we could all compare how far off our units are.

We do that with benchmarks.

 

Bret

[+Kai Team]

Sorry to be so blunt, ...

1. Your first point depends totally on the assumptions in your second.

 

2. Per Garmin, WAAS capable receivers typically have accuracies of 3-5 meters horizontally and 3-7 meters in altitude. My old, trusty GPS 3+ routinely was accurate to 12-15 feet. I don't feel like doing the metric conversion, but it doesn't appear that WAAS gives you an 80% improvement, does it?

 

BTW, who's non-WAAS GPSr is only accurate to 15 meters? Isn't that around 50 feet?

 

'Nough said.

It's nice that you got such great reception on your old GPS 3+, but one person's experience is, well, one person's experience. Depending on atmospheric conditions and satellite configurations, 40-50 foot EPE without WAAS is not unusual. So, let's compare what Garmin says to what else Garmin says:

 

15 meters: Typical GPS position accuracy.

< 3 meters: Typical WAAS position accuracy.

No need for metric conversion: 15-3=12; 12/15 = .80, ergo, 80% improvement. As Thot pointed out, those are also the specs used by Magellan. The FAA thinks WAAS improves accuracy, but what do they know? They're not dealing with anything as important as geocaching!

[+GrandpaKim]

Do you guys usually take a reading with your GPS right at the cache location then compare it to the published coordinates?

It would be interesting to have a cache that required everyone to post their coords and we could all compare how far off our units are.

 

Aloha,

Sam

Check out GPS Test Station. In order to log a find, you have to post the number of satellites you're picking up and the distance and bearing to the point while you're over the disk. These aren't the coordinates, but it does tell you how far off your GPSr is from the accuratly measured disk.

[+sbell111]

It's nice that you got such great reception on your old GPS 3+, but one person's experience is, well, one person's experience.    Depending on atmospheric conditions and satellite configurations, 40-50 foot EPE without WAAS is not unusual. ...

You're absolutely right, so lets take a quicky poll. Of those cachers who have cached without WAAS, does a 50 feet epe sound high?

 

From my experience, 40-50 feet is crazy high.

 

I had my old 3+ poxed up because I'm selling it on ebay, but I popped it out of the box and wandered outside to check the mail in the drizzling rain. In the time it took me to walk to my mailbox and back, the unit had locked onto 7 sats and showed an epe of 16 feet.

 

It has now been sitting on top of my computer in my office for about five minutes. It retains a lock on six sats and claims an epe of 18 feet.

 

Based on this, I believe that an epe of 40-50 feet without WAAS is very unusual. Further, your percentage of improvement due to WAAS cannot be true.

Edited June 11, 2005 by sbell111

[+sbell111]

Ooh looky. Now I have 7 sats and 16 foot epe, inside my home, on a rainy day.

[+Thot]

From my experience, 40-50 feet is crazy high.

 

<snip>

 

I believe that an epe of 40-50 feet without WAAS is very unusual.  Further, your percentage of improvement due to WAAS cannot be true.

This suggests you know more than Garmin about the subject.

 

Go to this page. Scroll down and read the data given on the bottom right of the page.

 

Three meters is 20% of 15 meters -- a reduction of 80%

 

edited to add:

 

And more than Magellan. Scroll to the bottom of this page.

Edited June 11, 2005 by Thot

[+sbell111]

Again, 50 meters is much greater of an epe than is normally experienced without WAAS. If you do not believe me, turn WAAS off and check for yourself. Is anyone getting an epe of 50 feet?

 

I love my old 3+, but I doubt that it is the best performing GPSr ever made.

Edited June 11, 2005 by sbell111

[+Hoppingcrow]

I cache without WAAS, using an ancient Garmin eTrex Summit. Seems to me like 50 feet is something I only get on a very, VERY bad day.