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GLONASS, RKP, CPT, active antennas, and other technologies...


BFG99
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I've generally been happy with the Garmin Vista HCx that I use - it locks on quickly, has WAAS capabilities and a stellar battery life. Plus, it doesn't have a lot of extra features I neither want nor need (camera, touchscreen, etc.) Perhaps my only complaint is one a lot of others have mentioned - it tends to drift a lot under heavy foliage or in dense areas, or fall victim to multipathing.

 

So I've been reading about emerging technologies to improve GPS technology. A GLONASS-capable receiver would be nice and based on testing would definitely help in heavy cover. But I've also read up on real-time kinetic positioning (RKP), carrier phase tracking (CPT), and the advantages of active antennae over passive ones (though admittedly I don't yet understand the difference).

 

 

So, here are four questions to help me decide whether to buy a new unit now, or wait:

(1) For those that have GLONASS-capable receivers...have you seen significant drift/multipath improvements in densely covered areas? Does it significantly diminish battery life or have any other negative side effects?

(2) Are there any RKP, CPT or active antenna handhelds out there? Any likelihood that there will be in the next couple of years?

(3) What about the new signals that will start being broadcast by the Block III GPS satellites? Will current units be able to understand/receive those signals, or will a new unit be necessary?

(4) Does Garmin (the manufacturer I'd probably stick with) post anywhere about units/technologies that are currently under development? I've been considering an eTrex 30 but would like to know what's in the pipeline first.

Edited by BFG99
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I've generally been happy with the Garmin Vista HCx that I use - it locks on quickly, has WAAS capabilities and a stellar battery life. Plus, it doesn't have a lot of extra features I neither want nor need (camera, touchscreen, etc.) Perhaps my only complaint is one a lot of others have mentioned - it tends to drift a lot under heavy foliage or in dense areas, or fall victim to multipathing.

 

Oh you already have the best GPS out there right now!

 

Keep it else you will be disappointed with all the new tech stuff as it is mostly bling and does nothing for base accuracy.

 

Upgrade at your peril!

 

:ph34r:

Edited by Odourless
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Oh you already have the best GPS out there right now!

 

Keep it else you will be disappointed with all the new tech stuff as it is mostly bling and does nothing for base accuracy.

 

Upgrade at your peril!

 

:ph34r:

 

I'm curious why you're so active on a Geocaching forum site yet you have no geocaching activity on your geocaching.com account.

Your anti-Garmin agenda is getting quite tiresome.

Yes, we get it. You like the older and simpler models better. Your preference has been noted.

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Heh, glad you guys let me know that that was a troll, since (despite caching for a while) I'm new to these forums and would have taken it at face value otherwise.

 

It seems getting a GLONASS capable unit (eTrex 30, perhaps?) would be a good investment, but I'd rather get answers to some of those other questions before I invest $200 or more in a unit that might be obsolete in 2 years.

 

EDIT: I should have mentioned I also have a Geko 201. That would DEFINITELY qualify as an "older, simpler" unit in their eyes!

Edited by BFG99
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Heh, glad you guys let me know that that was a troll, since (despite caching for a while) I'm new to these forums and would have taken it at face value otherwise.

 

It seems getting a GLONASS capable unit (eTrex 30, perhaps?) would be a good investment, but I'd rather get answers to some of those other questions before I invest $200 or more in a unit that might be obsolete in 2 years.

 

EDIT: I should have mentioned I also have a Geko 201. That would DEFINITELY qualify as an "older, simpler" unit in their eyes!

Regarding

#3, I would expect that to take a whole new chip so the current units will not be able to use the signals. From what I gather it will be a couple years before the signals will be available for use.

#4, Garmin does not give a very long view on the developments. Maybe a couple months before release they will release a announcement article and that is about all.

 

If you don't get the eTrex today what would you do? Wait for several years? But by then the next new thing will be on the horizon and just a few years away. That is the way technology works. You will be caching with the Vista for ever if you don't take the plunge.

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If you don't get the eTrex today what would you do? Wait for several years? But by then the next new thing will be on the horizon and just a few years away. That is the way technology works. You will be caching with the Vista for ever if you don't take the plunge.

Heh, I'd be lying if I said that hadn't occurred to me. But I'm typically conservative when it comes to technology - I don't buy a new computer or phone until the old one is beyond repair, even if it's hopelessly slow and out of date. Heck, I'm still driving the same car 15 years after buying it brand-new.

 

Since I'm largely happy with the Vista HCx, I'll probably just stick with it until it quits working or until a significant amount of technology (GLONASS, the new signals, capabilities described in question #2) becomes mainstream that it cannot access. So, another 2 years or so would be worth the wait in my opinion. That said, I still am curious whether any of the new technologies/techniques described in #2 are coming on board. Thanks for the responses in the meantime.

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I'll throw in my 2-cents.

 

The addition of GLONASS can make it faster to lock onto enough satellites to get a position during boot up, and makes it easier to hold enough satellites in otherwise difficult locations. That's because you unit now has twice as many satellites in the sky to look at. That doesn't necessarily equate to better accuracy (the estimate of your position vs. your true position), but it can equate to better precision (reduced standard error around the estimate).

 

The question is, how does this new fangled precision/accuracy improve what your current GPS can already do? If you're in a deep slot canyon, perhaps you'll hold a signal better than with an older eTrex. Under dense tree cover, the Oregons and 62 series, which don't have GLONASS, do pretty well. I hypothesize that it's because these "upper level" units have a better antenna than the entry level eTrex units have, especially the old-school eTrex line. I'm pretty sure the new ones are on par with the more advanced models.

 

Because your position is an estimate, any time you walk away from a location and return, you will get a slightly different reading. Hence the "multi-path." But that's also why drifting occurs. Your position isn't stable, but constantly being re-calculated, even when you're not moving. So, now let's ask the question: Why is this a problem? (or is it really a problem?)

 

Drifting while you're not moving can cause your track to be quite a bit longer than it actually is. That's kind of a pain when you're recording trip statistics or using your track for mapping. The multi-path is really only a problem if the difference between the paths is great (more than 50 ft) and if you're using the paths for mapping. But then, the way most people map trails is to hike them several times and take the average path. For placing waypoints such as geocaches, most of the new(er) GPS receivers have a waypoint averaging function to account for drifting.

 

Consumer-grade GPS's are not survey tools. If your location varies by 30 feet, you can still successfully navigate the wilderness, probably better than if you just had a map and compass. If having the latest technology is important to you and your budget allows for an upgrade, then by all means, upgrade. But, if you are on a budget but still looking to upgrade what you currently have, I find that buying an advanced unit one generation older maximizes value for the price. For example: The 62s retails for $199.99, cheaper than the eTrex 30. You do give up GLONASS, but you get a faster processor, better antenna, and increased file allowances than you do have with your current eTrex Vista Hcx.

 

Remember, the "latest technology" desire is a double-edged sword. You ask if you should wait for new technologies to be implemented. The reality is that Garmin could release new models in the near future with antennas capable of accessing other signals, and you could ask the same question: Should I buy now, or wait for the next upgrade?

 

In closing, I can't recommend the "correct" course of action. You've probably already made up your mind and are just looking for validation. But, if you're happy with your eTrex, but still desire something newer, I think you'll be happy with any of the current and last generation models out there (eTrex 30, 62s, 64s, Oregon 450, Oregon 600).

 

In response to questions 2-4, I don't think anyone really knows when new signal types and technologies will be implemented in consumer-grade GPS. Garmin is pretty good at keeping its developments a secret until the product is announced.

 

Hope this gives you some perspective and remember that technology doesn't make the experience. Have fun regardless of what GPS you decide to use.

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Take a look at the GPSMAP 62s if you can get it for around $200 -- the replacement model for it (the GPSMAP 64) came out recently, so the older 62s are heavily discounted.

 

I'll second this.

As sort of a GPS collector I prefer the 62S to any other unit I own or have used. In general when talking about reception in tough areas like under heavy canopy I find the single best feature is the quad-helex antenna.....I won't be getting another unit without one. The older Magellan Platinum and Garmin 60 CSx had the quad and are still great units but they lack the high sensitive receivers and paperless features the newer units have.

$200 for a 62S is the best deal EVER on ANY GPS.

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Because your position is an estimate, any time you walk away from a location and return, you will get a slightly different reading. Hence the "multi-path."
Good up to that point, but not hence, multipath. Multipath is a condition where a signal is reflected off of one or more objects, and while the receiver has access to two or more of the available direct and reflected signals. When the same signal is received twice or more (one original and one or more reflected, or two or more reflected), the time it takes for each to be received is therefore slightly different ... and timing of received signals is how this all works. This produces an odd combined signal to the receiver on the frequency in question, and even the best receivers have difficulty sorting out the subtle differences to figure out what's real and what isn't. Lesser receivers can push you off position significantly in the face of too many multipath signals.

 

But that's also why drifting occurs. Your position isn't stable, but constantly being re-calculated, even when you're not moving. So, now let's ask the question: Why is this a problem? (or is it really a problem?)
That is certainly real enough, and whether it is a problem depends upon the needed accuracy and the amount of drift that is occurring in the calculated position. Obviously, less is better, but one must beware of games played with the calculated position. 'Smoothing' can be employed to make a receiver look less drifty, but that has its downsides as well. Of all of the units I have owned, the least 'drifty' is my old Garmin Summit HC. You could sit it in the middle of the yard on a good day, and after letting it settle for a minute or two, it would drift less than 0.001 minute in both N/S and E/W over the course of an hour. How much was accuracy and how much was algorithm? Only the firmware boys at Garmin know for sure. Edited by ecanderson
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I had a Vista Hcx and lost it, then bought an Etrex 30. The 30 definitely gets a fix quicker and holds it better in poor conditions than the Vista. I can't comment on your other technical questions.

 

As with any technology there's always something new round the corner and you could be holding on forever if you keep waiting for the next thing to come along, however I have to say I don't think I would have traded up my Vista to the 30 if I hadn't lost it.

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I also have an hcx along with a 550t. I found that the hcx achieved lock much earlier than the 550 and was generally more accurate side by side when the 550 had waas enabled. Set the 550 to normal gps and there is no difference.the 550 is more advanced but better? I'm not so sure, if I hadn't got it for a bargain price, and I thought long and hard about buying it,i wouldn't have bought it. I do tend to use the hcx more as it is so much better on battery life.

I am undecided still about keeping the 550 but it will probably end up being my standby gps.

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Thanks everyone. I appreciate the feedback and would be interested in any more insight. I was hoping to find one or more of the GPSs out there used RKP, because that seems like a VERY promising technology...from what I understand, it measures the wavelength/pulse from each satellite to further refine the signal, often gaining a 5-10x accuracy and consistency improvement over the standard. But, I guess it'll be a while before we see that in consumer handheld units.

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ecanderson - That sounds like the same thing, however there have been some breakthroughs recently that show it could be doable on a handheld. I wasn't able to find the article, unfortunately, but just 2 weeks ago I read an article about a group that had demonstrated cheap handheld RKP receivers.

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So to get optimum accuracy, we need to place a reference receiver near each cache? Unless WAAS/EGNOS or similar (with their own 'reference' receivers) start producing much tighter values and more localized results, I don't see how one gets the full benefit of the technology. We're still at the mercy of whatever errors are caused by atmospheric conditions.

I'd like to see some good stats on how well they're doing sans the reference receiver.

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Perhaps I'm reading it wrong, but I don't think you'd have to have a reference receiver at each geocache. Obviously that wouldn't be doable. The way I read it, you just have to have a second receiver nearby - in your pocket, in the car, etc. - and that would be enough to calculate the ionosphere interference. And, even if the ionosphere interference isn't cancelled out, the remaining components of RKP would still allow for higher precision.

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So to get optimum accuracy, we need to place a reference receiver near each cache? Unless WAAS/EGNOS or similar (with their own 'reference' receivers) start producing much tighter values and more localized results, I don't see how one gets the full benefit of the technology. We're still at the mercy of whatever errors are caused by atmospheric conditions.

I'd like to see some good stats on how well they're doing sans the reference receiver.

I would be happy to provide the process by which you could determine these performance characteristics. However, I am somewhat reluctant to do so as my previous efforts to convey QUANTITATIVE performance data resulted in accusations of my having performed pseudo-science.

 

Now, if I could be assured that......... :)

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I've never taken too much notice of the satellite settings before, I set them when I got it and have pretty much left them unchanged and as long as it gets a fix and is giving me some numbers to navigate by I'm happy. But having followed this thread I paid attention on my trip out today, and in Portsmouth (Southern UK) and also at home (North Hampshire) I got a WAAS/Egnos lock within a minute or two although the initial lock was a matter of seconds (with GPS and GLONASS enabled) - a "D" in the satellite bar does mean it's using Differential GPS yes?

 

One of these days I might go out and have a proper play with all the options and see for myself how much difference it makes.

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Yep, "D" means differential GPS, i.e. the GPS satellite and WAAS/EGNOS are both being taken into account. It's not a surprise that it took longer to lock onto WAAS/EGNOS...my understanding is that they only broadcast every 90 seconds or so.

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