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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Post your bird's GPS or radar-clocked top speeds
01-15-2006 12:35 PM  13 years ago
Yug

rrMaster

UK. Herts

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Oops forgot to post. Hiya, yes. It was rather disappointing as I only got 64mph. It's a good job I'm not intending to have a go at drag racing just yet
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01-15-2006 12:38 PM  13 years ago
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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What bird/engine/airtemp/wind, etc, Guy?op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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01-15-2006 06:51 PM  13 years ago
Yug

rrMaster

UK. Herts

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XeroG50, SAB600s, Hyper50, MP2, Magnum30, HS=1950, 5degC, 12mph cross wind, Numb thumbs, Hungry tummy.
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01-15-2006 07:42 PM  13 years ago
Heliavi8or

rrApprentice

Temecula, CA

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They are faster than I thought they were.Practice! It might be costly but it's the only way we get better!
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01-16-2006 02:58 AM  13 years ago
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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Guy, your setup is nearly identical to mine. You gotta do that again when there's less wind. Are you running equal and maximum amounts of up and down collective?op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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01-16-2006 06:39 AM  13 years ago
Helge-heli

rrApprentice

Eureka,Calif

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I got 78 mph clocked downwind forward flight with my Raptor 70.
Handheld radar detector the kind for clocking baseballs
Trex 700E-FC3,Trex600,Trex 700Nitro pro, Raptor 90 OS- 91~Raptor70 MD-500,MA-Razor~Cool power30%
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01-16-2006 06:58 AM  13 years ago
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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How much tailwind?op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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01-16-2006 08:46 AM  13 years ago
Yug

rrMaster

UK. Herts

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+/-10. I'll give it another go next weekend. Wont be changing the setup cos it my 3D battleaxe.
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01-16-2006 10:21 AM  13 years ago
GroundPounder

rrVeteran

South Africa, Cape Town

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I haven't had the guts to put my GPS on my Rappy 50 yet, but I do use it to log all my hanggliding flights, and as far as I can make out, it only records horizontal speeds.
I'm using a Garmin 76S, and SeeYou to analize my flights.
GroundPounder
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01-16-2006 04:32 PM  13 years ago
spork

rrVeteran

Mountain View, CA

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Groundpouder,

I'm not specifically familiar with the 76S, but my bet is that it can output NMEA strings that include Lat, Lon, and Altitude. I suspect it also can record a path which can then be dowloaded to your computer including altitude. It probably doesn't display altitude on the screen (although it might if you go into the menu to edit the path or recorded points). I use a Garmin III+ to record my hang gliding flights. Never flown in South Africa. Good flying there?

If you do find you can download your points in 3D I have a freebie program that will let you examine your path (and move around to view it from any angle).

RC
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01-17-2006 06:18 PM  13 years ago
GroundPounder

rrVeteran

South Africa, Cape Town

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Hi spork, a fellow hangie, imagine that!
Yes, the 76S logs flights in IGC format, the SeeYou program allows you to zoom in to the point where you can visualise the actual thermals!
And overlayed on vector/raster maps/satellite pics.
Flying here is good, we've just had our Nationals, some huge out and return flights around turnpoints, my longest flight in the comp was 3 hours 45 min.
Took my RC stuff with, had one rainy day, flew the plank and the Rappy!

Hopefully I'll make Wallaby this year, been meaning to for a while now.
GroundPounder
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01-22-2006 12:59 AM  13 years ago
tchavei

rrProfessor

Portugal

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Hi again Folks


Garmin etrex appeared at my doorstep today.

Took it with me to the field and strapped it under the canopy on my Evo 50 (10% nitro, OS50sx-h non Hyper max 10 pitch) and did a normal flight. I punched the pitch a couple of times and after landing I got 72mph max speed which is pretty standart for my flying (didn't do any large highspeed circles)

When I got home I started to investigate PC software for data analisis etc. I was able to download the track data from the gps device. The altitude stays recorded. Seems I was up to 420 feet? (Jeez, I didn't know I flew that high)

The wierdest is that on a couple of fast flyby's (as seen on the graph I plotted) The top speed is around 98mph?!?!?

I believe more the 72mph than the 98mph but why did the 98mph appear on some routes and why was the max speed read as 72mph?

Tony

--------------------
"Perfection and patience usually walk side by side..."
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01-22-2006 02:09 AM  13 years ago
heli_headcase

rrKey Veteran

Hovering around Atlanta

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I believe more the 72mph than the 98mph but why did the 98mph appear on some routes and why was the max speed read as 72mph?
It's possible that the speed has to sustain a rate for a given minimal time to be recorded as valid max velocity data. Anyone else want to comment on this?

What software was used to download the flight? Where did you find it?

Thanks,
Steve.
.
.

HHC

So many heli's - too little time...
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01-22-2006 03:32 AM  13 years ago
spork

rrVeteran

Mountain View, CA

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The wierdest is that on a couple of fast flyby's (as seen on the graph I plotted) The top speed is around 98mph?!?!?

I believe more the 72mph than the 98mph but why did the 98mph appear on some routes and why was the max speed read as 72mph?
As I recall the best case RMS errors for non-differential, code-phase GPS is somewhere around 15 feet. So it's possible your graph is showing speed as DX/DT where two subsequent samples have an error of 15 ft in opposite directions. This could have you flying an extra 30 feet in the 1 second between GPS samples. This would be an uncommon situation, but certainly not impossible. I've seen subsequent GPS readings change by hundreds of feet when a satellite is lost or acquired. To get a better idea of the velocity directly from position fixes you'd be better off going several samples to either side of the point in question. You might also want to slide your sample area forward and backward in time to make sure you're not bridging a discontinuity. When you look at the velocity output from the GPS unit you're probably getting a better estimate that is computed internally in a different way.

RC
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01-22-2006 09:37 AM  13 years ago
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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I believe Spork hit the nail on the head with that reason for odd momentary high speed readings.

It would also seem that many units do not include altitude info in their respective data streams. Despite the many useful functions of the GPS system, one area it's lacking in (for consumer-level products anyway) is in accurate altitude calculation. It's a byproduct of the geometry of the nominal positions of the 32 satellites. In other words, even with 12 birds above the horizon and evenly spread throughout the sky (a rare occurance) and while sitting at a high elevation, the GPS reading will vary at least 200' for altitude while less than 8' for location. A friend along for the trip was getting the same performance out of her Magellan handheld.

In order to record an accurate speed in any vehicle its been my experience over seven years of fooling around with the Garmin handhelds that speed MUST be maintained steadily for at least 2-3 seconds. Not a problem for RC applications.

For GPS runs I fly slowly to a position at the downwind end of the runway, then accelerate (straight and level) 'til the end of the runway (700' where I'm at). Then I do a steep, near-zero collective stall turn so as not to accelerate while descending back into level flight again. Then max acceleration downwind to max speed again.

Land. Assess wind speed. Read GPS top speed.

Of course the downwind run will be the one that provides max speed. The purpose of max power in both directions is to use visual and audio cues to better assess wind speed.
op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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01-22-2006 04:27 PM  13 years ago
spork

rrVeteran

Mountain View, CA

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Despite the many useful functions of the GPS system, one area it's lacking in (for consumer-level products anyway) is in accurate altitude calculation. It's a byproduct of the geometry of the nominal positions of the 32 satellites. In other words, even with 12 birds above the horizon and evenly spread throughout the sky (a rare occurance) and while sitting at a high elevation, the GPS reading will vary at least 200' for altitude while less than 8' for location
It's true that the geometry of visible satellites affects the accuracy of altitude readings more than it does the lat-lon readings. This is because the earth is in the way of all the satellites below you. My recollection is that the GDOP (geometric dillution of precision) is 1.7 times worse in altitude.

I use my Garmin III+ on my hang glider and while flying full-scale sailplanes. I've found a repeatability of about 15' in lat-lon with good satellite coverage, and about 30' in altitude (based on runway altitude and ridge height). It's certainly true that some units will trade-off altitude for lat-lon accuracy however.

Interestingly (I think), we put high end GPS units in NASCAR vehicles, and get 2cm accuracy in X/Y using differential GPS and resolving carrier phase. I have a friend that's done something very similar to compute the position and attitude of auto-piloted helicopters (for the Robotic Aerial Vehicle competition).

RC
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01-22-2006 09:15 PM  13 years ago
Mattiward

rrApprentice

160ft off the deck 10ft from 400,000 volts - U.K.

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I managed to get 134mph with my Rappy 50 Hyper straight n level.

Then I ran out of runway - it was the only way I could think of securing my GPS to the bottom of my heli.

(sat nav in a Cooper S) sorry is this cheating???

Then I thought of another way - get a Tom Tom and try that....
Bit blurry but you can make out the 185mph.
http://www.tomtom.com/plus/gallery/view.php?ID=840&;CID=2&Language=1

This time though I was using the 3rd heli in my fleet rather than my Rappy (see Profile)

Regards

Matt


Full size helis are flying cooling fans -
turn the big fan off & watch the Pilot sweat...
Then it all goes quiet & the cows get bigger!!!
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01-22-2006 09:42 PM  13 years ago
tchavei

rrProfessor

Portugal

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Hi again
What software was used to download the flight? Where did you find it?
I used GPS Trackmaker (http://www.gpstm.com) to download and analyse data. It plots nice graphs of our route... I do nice figure 8s

The important is to set tracklog to 1 sec update on the garmin so you have as much detailed data as possible. Don't forget to set it up so It doesn't overwrite data when memory becomes full.

I'm in the process of fabricating a stand for my etrex so I can put it under the canopy.

Cheers
Tony

--------------------
"Perfection and patience usually walk side by side..."
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01-22-2006 09:48 PM  13 years ago
GimbalFan (RIP)

rrProfessor

Big Coppitt Key, FL

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"we put high end GPS units in NASCAR vehicles, and get 2cm accuracy in X/Y using differential GPS and resolving carrier phase."

I spoke to a surveyor recently who said that GPS receivers for his profession were accurate to within 3mm with no external differential devices required. That's the one that I want, along with a helicopter big enough to lift it. It was about the size of a shoe box and around 5 pounds.
op-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-thwop-t
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01-23-2006 12:10 AM  13 years ago
spork

rrVeteran

Mountain View, CA

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I spoke to a surveyor recently who said that GPS receivers for his profession were accurate to within 3mm with no external differential devices required.
For surveying purposes you can achieve carrier-phase lock by letting the RX sit still long enough for the satellite constellation to change (20 mins?) Since the race cars are going close to 200 mph we don't have that luxury. We use every trick we can think of to maintain carrier-phase lock, including inertial measurement units (IMU's), very accurate track maps (an approach we patented), and differential GPS stations.

The day may not be too far off when those kind of accuracies will be achieved by consumer devices. I look forward to it.

RC
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Home✈️Aircraft🚁HelicopterHelicopter Main Discussion › Post your bird's GPS or radar-clocked top speeds
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