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Old Jan 24, 2013, 10:14 PM
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Voltron Mini GPS How Accurate for Speed Data??

Anyone have some feedback on this particular gaget? How accurate are they really? I personally have doubts but I'd like some other opinions.
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Old Jan 24, 2013, 10:52 PM
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Old Jan 24, 2013, 11:15 PM
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http://www.rcgroups.com/forums/showt...ltron+mini+gps
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Old Jan 25, 2013, 01:42 AM
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GPS is generally no good for us in high performance airplanes. They tend to be too slow at picking up positions and then calculate your speed based on inaccurate positions. There's plenty of videos on youtube where gps shows planes going much faster than you know it could have gone.

For slower planes, it's probably ok.
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Old Jan 25, 2013, 02:29 AM
I am actually really slow
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Should be called the Placebo GPS. Makes everything go 200mph.

I read something a while ago saying that unless you have military connections GPS units are limited/no good for high speed stuff in general and you need proper licenses to own truely accurate GPS systems. Something to do with preventing an everday person putting a Garmin inside a home built cruise missile. Not sure if there's any truth to that but interesting all the same.

It would kinda make sense though as GPS should be without a doubt the most accurate way to measure the speed of something. Gps Satellites Atomic clocks are theoretically accurate to under 20 nanoseconds.

Maybe because most of us are just general members of the public, we're getting cut short with GPS capabilities. Its also probably why no one seems to have a great deal of success with the voltron unit.
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Old Jan 25, 2013, 04:51 AM
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3s@600-700 watts turn left pylon , wrong numbers ??
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Old Jan 25, 2013, 06:23 AM
Crashing into the sky!
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That seems legit
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Old Jan 25, 2013, 09:35 AM
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Quote:
Originally Posted by SlowBarless View Post
Should be called the Placebo GPS. Makes everything go 200mph.

I read something a while ago saying that unless you have military connections GPS units are limited/no good for high speed stuff in general and you need proper licenses to own truely accurate GPS systems. Something to do with preventing an everday person putting a Garmin inside a home built cruise missile. Not sure if there's any truth to that but interesting all the same.

It would kinda make sense though as GPS should be without a doubt the most accurate way to measure the speed of something. Gps Satellites Atomic clocks are theoretically accurate to under 20 nanoseconds.

Maybe because most of us are just general members of the public, we're getting cut short with GPS capabilities. Its also probably why no one seems to have a great deal of success with the voltron unit.
It's called DGPS or differential GPS. I work with it in UAV's everyday. While it is highly accurate position data, it still isn't the most accurate for speed. The best it can measure is ground speed which is obviously affected by wind. Airspeed is the only true way to know how fast your plane is going. Radar, GPS & doppler are nice ways to get a WAG, but a pitot/static system is much, much more accurate. Most people don't grasp this concept.

Humorous side note, I got into a nice "discussion" with a mental giant on RCU who swore his plane turned more rpms down wind than up. He was convinced that the tail wind would give his plane an extra push and got it up on step. He "proved" it by citing rpm differences in the waveOscope files upwind vs. down. He couldn't understand the simple fact that he was measuring ground speed, not air speed, and therefore the different rpms sounded different due to the wind changing the aircraft's ground speed to him and not air speed. Good laughs.

Red
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Old Jan 25, 2013, 11:12 AM
I am actually really slow
SlowBarless's Avatar
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Originally Posted by sebbe View Post


3s@600-700 watts turn left pylon , wrong numbers ??
Didn't know you could throw that hard Sebbe

Thanks for clearing that up Alien Tech.

Interesting points about ground and air speed. Doppler can be a confusing thing sometimes. I don't blame him for getting confused though, it took me ages to understand the concept. It was only when I first heard the F3D models going around the pylons that it finally clicked.
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Old Jan 25, 2013, 11:48 AM
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Thanks Red, very interesting.
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Old Jan 26, 2013, 08:41 AM
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Now are these units even in the ballpark?
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Old Jan 26, 2013, 10:05 AM
I am actually really slow
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Not on these models, no..

They may throw up an accurate figure everynow and then but, how would you know what numbers are accurate or not if you're relying on the gps to tell you the speed in the first place.
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Old Jan 26, 2013, 01:14 PM
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Short answer is - Not even close!

Probably would work for a hobbyzone supercub flown in nice big gentle circuits, anything else forget it.

There are umpteen threads with people using GPS speeds, claiming their HK foam warbird is suffering from mach tuck, please dont add your self to the list of "one of those people"

If you want accurate airspeeds pitot static sensors work well, they can be made to throw goofy numbers but its much harder to do than GPS. Eagletree/Winged shadow and others make em.
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Old Jan 26, 2013, 01:35 PM
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I have to jump in here and say something, The voltron has it's moments and can be way out at times, I have run it in my Multiplex Dog fighter with eagletree pitot tube and was pretty much bang on in 3 different runs. the GPS had picked up 13 satellites at that time
This is my personal experience with it that's all
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Old Jan 26, 2013, 01:50 PM
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Originally Posted by jackosmeister View Post
Short answer is - Not even close!

Probably would work for a hobbyzone supercub flown in nice big gentle circuits, anything else forget it.

There are umpteen threads with people using GPS speeds, claiming their HK foam warbird is suffering from mach tuck, please dont add your self to the list of "one of those people"

If you want accurate airspeeds pitot static sensors work well, they can be made to throw goofy numbers but its much harder to do than GPS. Eagletree/Winged shadow and others make em.

I have used the winged shadow systems pitot unit. My purpose behind starting a thread on this was just to get some opinions on it good or bad. It seems to me that GPS is not the way to go for sure, just from what I've read so much about in other threads.
There are definately some rediculous speed claims out there from GPS, because just from my experience with years of flying nitro speed stuff and I know what it takes to go some of these claimed speeds and its just impossible, so GPS must be off a bunch.
These GPS units are giving people false bragging rights.
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