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Are ("H") High sensativity units really better?


Buck&Abby
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I currently have a vista C and I'm curious if the "H" or high sensitivity model is really that much better? Most of the Garmin units seem to have made a switch over to the "H" models? Wonder if its just a sales ploy or if they are much better? any help would be appriciated. thanks

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I currently have a vista C and I'm curious if the "H" or high sensitivity model is really that much better? Most of the Garmin units seem to have made a switch over to the "H" models? Wonder if its just a sales ploy or if they are much better? any help would be appriciated. thanks

 

Yes, they definitely work better. I have had a few eTrex's over the years and my Vista HCx does a great job holding a satellite lock under difficult conditions (tree canopy, etc.).

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My old blue eTrex legend frequently lost sat lock in even light forested conditions - sometimes under a single tree. My Legend HCx keeps a solid lock in heavy dense cover in hilly terrain.

 

No contest.

There aren't many trees or tall buildings around where I live so my torture test is my basement office. I get six to eight satellites with my Legend HCx sitting right under a bunch of metal heating ductwork. It is genuinely a marvel that it gets a 3D lock down here.

 

...ken...

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I currently have a vista C and I'm curious if the "H" or high sensitivity model is really that much better? Most of the Garmin units seem to have made a switch over to the "H" models? Wonder if its just a sales ploy or if they are much better? any help would be appriciated. thanks

 

Personally I"m not sure. I don't have an H, but now have a 60CS which is more sensative than the GPS V. Overall the GPS V performs better. It's true that I can now get a lock inside my house much better, but when actually trying to get to ground 0, the V does a better job. The 60 has me wander about more.

 

My theory (and I could be wrong) is that it's not enough to have more sensatvity, you also need what I'm going to call "clarity". Think about AM radio. At night you can get the equivilent of more 'sensativity' but the stations are not as clear. If you had a filter that can pull out the static and interference you could do a lot better. Pulling a signal through more tree's and through the roof of my house is great, but if the GPS can't compensate for the signal degridation that's taking place in some way, you are going to get more goofy information as well. Call it GPS static.

 

The 60 can point when the V can't point at all,but when the V point's it does a better job.

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Personally I"m not sure. I don't have an H, but now have a 60CS which is more sensative than the GPS V. Overall the GPS V performs better. It's true that I can now get a lock inside my house much better, but when actually trying to get to ground 0, the V does a better job. The 60 has me wander about more.

Yes, but the 60 Cs doesn't have a high sensitivity receiver either - they are both "old" technology.

 

Now, if you tried the same experiment with a 60 CSx, or an eTrex "H" series or similar, you would see some REAL improvement in sensitivity, which results in MUCH better ability to get and hold a fix in all sorts of sub-optimal conditions.

 

In ideal conditions (open sky, free of buildings, tree cover, etc), you won't necessarily get more accuracy out of the new units (but you will probably find the new high sensitivity receivers are much quicker to get a location fix from a warm or cold start), but you will certainly see the difference as soon as you move to a location with partial shielding etc.

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For geocaching, I use my fairly new Etrex Vista HCx and my wife uses my old 76C. The Vista HCx acquires much faster and has never lost a lock. The 76C is slower to acquire and looses satelitte reception quicker. However it seems to be much more accurate in finding GZ. This is just my observation. Dick

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Personally I"m not sure. I don't have an H, but now have a 60CS which is more sensative than the GPS V. Overall the GPS V performs better. It's true that I can now get a lock inside my house much better, but when actually trying to get to ground 0, the V does a better job. The 60 has me wander about more.

Yes, but the 60 Cs doesn't have a high sensitivity receiver either - they are both "old" technology.

 

Now, if you tried the same experiment with a 60 CSx, or an eTrex "H" series or similar, you would see some REAL improvement in sensitivity, which results in MUCH better ability to get and hold a fix in all sorts of sub-optimal conditions.

 

In ideal conditions (open sky, free of buildings, tree cover, etc), you won't necessarily get more accuracy out of the new units (but you will probably find the new high sensitivity receivers are much quicker to get a location fix from a warm or cold start), but you will certainly see the difference as soon as you move to a location with partial shielding etc.

 

Better lock is fair, however I wasn't talking about the ablity to hold a signal. Still since the H recieves are supposed to be better still than the improvments in the first 60 series I'd have to borrow one and see what happens when it comes to the "just guide me to the cache without making me walk like a drunken sailer" problem I've noticed with the better reciver I do have access too.

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My 60Cx takes me straight towards the cache every time. Once the cache is within the circle of accuracy it's anyone's guess, but to get me that far it's spot on.

 

Just after I bought my 60Cx I needed to go into a supermarket. I put the 60 in my pocket rather than leave it in the car. When I looked at the tracklogs that evening, to my amazement, there I was wandering up and down the aisles in the supermarket - the gps had stayed locked on and tracking just from what it could glimpse through the front windows, and it was a big supermarket. I was impressed ...

 

Gary

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I currently have a vista C and I'm curious if the "H" or high sensitivity model is really that much better? Most of the Garmin units seem to have made a switch over to the "H" models? Wonder if its just a sales ploy or if they are much better? any help would be appriciated. thanks

 

It's early days for me with my new toy - Oregon 400T - but I've been having similar thoughts. I seem to get quite wild swings when approaching a waypoint/cache etc. and slow responses and ill-defined swings when I'm back-tracking and miss a turning. I had much more positive and speedier responses with my old yellow (non-H) eTrex - although of course it was no good when under forest cover etc. - my main reason for initially looking for an upgrade.

 

Still wondering if I wouldn't have been better off with a Legend HCx or 60Cx :unsure:

 

JsR

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One must keep in mind that they are not really more "sensitive". Some units like the 60CS were just as "sensitive" as the current units. The difference is that they USE the weak, multipath signals in their position calculations. The older units ignored the weak signals because they did not try to use the multipath.

 

Most of the time, the fancy calculations work, sometimes they go nuts.....

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One must keep in mind that they are not really more "sensitive". Some units like the 60CS were just as "sensitive" as the current units. The difference is that they USE the weak, multipath signals in their position calculations. The older units ignored the weak signals because they did not try to use the multipath.

Red90,

 

I'm not sure that is totally correct. My understanding is that "sensitivity" refers to the strength of signal which can be acquired and used. An instrument which can acquire and use a signal in a particular time and place is by definition "more sensitive" than another which cannot.

 

What the GPSr's algorithm does with that signal if / when it has been received (i.e. use it or ignore it) is another matter. A "smart" algorithm would use all available signals to acquire a fix when necessary, but would then interrogate the "quality" of each signal, and would logically "de-rate" or even ignore a particular poor-quality signal when there are more than the bare minimum number of signals required to get a 3D fix. This task could be accomplished partly by the chip-set hardware and firmware (i.e. provided by the chip-set manufacturer), and partly by the unit's software (e.g. provided by Garmin). I have no idea whatsoever what any version of Garmin hardware / software / firmware do! :unsure:

 

Conventional GPS receivers ... acquire and track signals down to around the -160 dBW level. High Sensitivity GPS receivers ... acquire signals up to 1,000 times weaker. A good High Sensitivity GPS receiver can acquire signals down to -185 dBW, and tracking can be continued down to levels approaching -190 dBW.

 

http://en.wikipedia.org/wiki/High_Sensitivity_GPS

 

I don't know for sure what receiver each Garmin model has, but there are definitely some GPSrs which DO have higher sensitivity than others. My Summit HC has MUCH higher sensitivity than my old yellow eTrex, my car sat-nav (no-name Chinese import), or my Samsung phone (if higher sensitivity is indicated by time to acquire a fix, and conditions under which that fix can be maintained).

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In a "traditional" GPS, the position algorithms assume that the signal is direct and not reflected. If the signal is below a certain strength, it assumed to not be direct and be reflected. The units purposely did not use the reflected signals as that would give the incorrect location. This is one of the reasons that the GPS transmissions are weak to begin with (to avoid reflections).

 

The new units use all of the signals and with crazy math decide how many times they have reflected to create a position. This does magic sometimes. The problems occur when there are less than 3 direct signals being read. When all of the signals are reflected, the math can lead to incorrect calculation of position.

 

I'm only saying this because the newer units can "appear" to be creating a good position and show strong satellite signals while still giving you the wrong location. The older units were more "honest". You had good signal and good position or not.

 

In the end, from field experience and reviewing and comparing a lot of track data, the new units are better most of the time, but not all of the time. Some chip brands have better figured out the math than others.... Have a look at the Oregon, they change the GPS performance drastically with every firmware which is all due to the math...

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Conventional GPS receivers ... acquire and track signals down to around the -160 dBW level. High Sensitivity GPS receivers ... acquire signals up to 1,000 times weaker. A good High Sensitivity GPS receiver can acquire signals down to -185 dBW, and tracking can be continued down to levels approaching -190 dBW.

 

http://en.wikipedia.org/wiki/High_Sensitivity_GPS

 

Not sure why this article uses dBW. No one uses dBW. Every GPS manufaturer uses dBm (exept Garmin who doesn't list any power level. Let me translate the above statment for you into dBm.

 

Conventional GPS receivers ... acquire and track signals down to around the -130 dBm level. High Sensitivity GPS receivers ... acquire signals up to 1,000 times weaker (30dB lower). A good High Sensitivity GPS receiver can acquire signals down to -155 dBm, and tracking can be continued down to levels approaching -160 dBm.

Edited by Andronicus
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We have a legend Cx and we lose satts all the time. Our uncle (Michigan Cacheman) has a Vista HCx and he gets ten satts sitting in his house we only wish we could do that. The other thing is if we stand still are GPS jumps all over the HCx will point the right way all the time.

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We have a legend Cx and we lose satts all the time. Our uncle (Michigan Cacheman) has a Vista HCx and he gets ten satts sitting in his house we only wish we could do that. The other thing is if we stand still are GPS jumps all over the HCx will point the right way all the time.

 

This would be because of the compasses, I believe. Someone with more knowledge can jump in and correct me if I'm wrong!

 

Just checked out your location, we might just make it up to you this year, beautiful area!

Edited by Rockin Roddy
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...has a Vista HCx and he gets ten satts sitting in his house we only wish we could do that.

 

Correct, BUT.....

 

That does not mean he is getting a better location fix. In the house all of the signals are reflected. Because of that it is impossible to determine (mathematically) your actually position. There are only probable positions and the unit shows you the "most" probable, which may or may not be the correct one.

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...has a Vista HCx and he gets ten satts sitting in his house we only wish we could do that.

 

Correct, BUT.....

 

That does not mean he is getting a better location fix. In the house all of the signals are reflected. Because of that it is impossible to determine (mathematically) your actually position. There are only probable positions and the unit shows you the "most" probable, which may or may not be the correct one.

 

You can correct me if I'm wrong, but having a sat fix is better than not having one...right? It may not be completely accurate, but it does show that it does get better reception.

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"having a sat fix is better than not having one...right? It may not be completely accurate, but it does show that it does get better reception."

 

If you had last used your GPS unit in Iowa, and turned it back on in Oregon, the unit without a fix would show you in Iowa. Personally I would prefer to have a poor fix (and know which state I'm in) than no fix. The EPE should give you some idea of how accurate the fix is. The worst case I've seen in around 1000 feet. I believe the newer chips are definitely more sensitive, and that to me is very worthwhile.

Edited by GeoBobC
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We have a legend Cx and we lose satts all the time. Our uncle (Michigan Cacheman) has a Vista HCx and he gets ten satts sitting in his house we only wish we could do that. The other thing is if we stand still are GPS jumps all over the HCx will point the right way all the time.

 

This would be because of the compasses, I believe. Someone with more knowledge can jump in and correct me if I'm wrong!...

 

If you use the electronic compass it does point the way all the time. Without it the pointer jumps around when you are standing still (or going below a certain threshhold speed)

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In a "traditional" GPS, the position algorithms assume that the signal is direct and not reflected. If the signal is below a certain strength, it assumed to not be direct and be reflected. The units purposely did not use the reflected signals as that would give the incorrect location. This is one of the reasons that the GPS transmissions are weak to begin with (to avoid reflections).

 

The new units use all of the signals and with crazy math decide how many times they have reflected to create a position. This does magic sometimes. The problems occur when there are less than 3 direct signals being read. When all of the signals are reflected, the math can lead to incorrect calculation of position.

 

I'm only saying this because the newer units can "appear" to be creating a good position and show strong satellite signals while still giving you the wrong location. The older units were more "honest". You had good signal and good position or not.

 

In the end, from field experience and reviewing and comparing a lot of track data, the new units are better most of the time, but not all of the time. Some chip brands have better figured out the math than others.... Have a look at the Oregon, they change the GPS performance drastically with every firmware which is all due to the math...

 

Thanks.

You confirmed what I suspected. The "Old" new GPS That I have must not yet have the better math since it has me wander around more than my "old old" GPS that is more honest. Or maybe I'm washed up on this.

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...has a Vista HCx and he gets ten satts sitting in his house we only wish we could do that.

 

Correct, BUT.....

 

That does not mean he is getting a better location fix. In the house all of the signals are reflected. Because of that it is impossible to determine (mathematically) your actually position. There are only probable positions and the unit shows you the "most" probable, which may or may not be the correct one.

Yes. And it's unlikely to be a stable position. When I fire up my eTrex Legend HCx in my basement office and connect it to my PC with GPSView running, the chart plot shows constant movement. It's unbelievable how fast and how far this old house can move! It never settles, no matter how long you leave it running.

 

If I take the laptop and Legend out onto the deck in the backyard the position information is hugely more stable. It only takes a few seconds to start to settle and stop all the twitching.

 

I am still impressed at how well it works in a variety of awful conditions and I wouldn't give it up for a second. For general navigation use on a hike or mountain bike ride with a good set of topos on the card it's still very usable even in difficult conditions. But I also don't delude myself that the increased sensitivity necessarily translates into better accuracy.

 

...ken...

Edited by Ken in Regina
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If you had last used your GPS unit in Iowa, and turned it back on in Oregon, the unit without a fix would show you in Iowa. Personally I would prefer to have a poor fix (and know which state I'm in) than no fix.

No, they're both going to behave in pretty much the same fashion. After a short while, they're both going to display a Position Fix Error display, and give you the option of setting your position, or performing auto-location. The idea that an "H" receiver will just keep on showing you in the wrong place is ridiculous.

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Prime Suspect perhaps you don't understand my post. A high sensitivity receiver will acquire a fix where a lower sensitivity unit may not. If you turn a unit off in one location, and move, the map will display the most recent location until a new fix is acquired. The higher sensitivity receiver will acquire a new location whereas the other may not. Thus the units turned off in Iowa and turned on in Oregon will both display Iowa, until a new fix is acquired. In other words, I would prefer to fix any fix, even a poor one, rather than no fix. That's why I greater prefer the higher sensitivity models like the H and X series.

Edited by GeoBobC
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