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Costyn

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Another possibility that may have occurred and may explain the readings you obtained. Is/was your barometric altimeter on?

Being that the receiver is on the side of your head and the barometric altimeter is affected by changes in the airflow, just like the Neptune/Protrack can be when the head is turned, there is the possibility that may be why your readings are all over the place.

While the top of the helmet is an ideal place to mount the GPS receiver, it can be affected by turning ones head or changing the airflow around the receiver when the barometric altimeter is on. The barometric altimeter is far more accurate(like the one in the aircraft) than the GPS adjusted altitude readings but the trade off is that it has to be calibrated (just like the pilot does ) in order to get precise readings and it can be affected by distruptions in the airflow(turning ones head). Personaly, I choose to leave the barometric altimeter on and I ensure I calibrate it beforehand and that I have proper/ideal recevier placement so I get consistant readings. Garmin says that when properly calibrated, the barometric altimeter is accurate to within 10ft. If one relies on the GPS calibrated and adjusted altitude, Garmin says altitude readings will be greater than 10 ft off.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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The barometric altimeter is far more accurate(like the one in the aircraft) than the GPS adjusted altitude readings.



Hello Scott

Look's right if the vertical speed is regular and slow.
Experiments shows that GPS with barometric capsule gives strange verticale speed graph.

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Personaly, I choose to leave the barometric altimeter on and I ensure I calibrate it beforehand and that I have proper/ideal recevier placement so I get consistant readings.



Some GPS techniciens explained us that gps with barometric capsule are mixing both altimetric and GPS altitudes informations in the log. They advize us to turn barometric capsule off to have less noize in the log. Do you agree? if you can understand my french tranlated to english :)

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Did you beat Costyn then :P.

Kris.



Hehehe. Yeah, bring on the TrackingDerby graphs! :P This is the TrackingDerby.com wingsuit section thread after all. ;) Not that I really care, but I find it a bit more difficult to interpret the Excel graphs.

Anyways, looks like I laughed too soon. Someone else already beat me.

Cheers
Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News

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Is/was your barometric altimeter on?

Being that the receiver is on the side of your head and the barometric altimeter is affected by changes in the airflow, just like the Neptune/Protrack can be when the head is turned, there is the possibility that may be why your readings are all over the place.



That's what I'm saying. It's not the loss of the GPS signal strength (otherwise both horizontal and vertical speeds would be noisy), it's Vista C's freakin' barometer which is totally useless for skydiving.

Do you know the way to turn it off and use GPS altitude only?

BTW, I kept my head in fixed position specifically to get better data.
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

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Did you beat Costyn then . :P

Kris.



I don't compete. I just love the feeling of ripping through the air and hauling ass across the ground. :) (former theoretical/experimental physicist)

For those who do compete, you can cover greater horizontal distance in 90s if you collapse the arm wing. 135mph * 90s = 3.375mi, and that's without any tailwind!

Yuri
Android+Wear/iOS/Windows apps:
L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP
iOS only: L/D Magic
Windows only: WS Studio

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Some GPS techniciens explained us that gps with barometric capsule are mixing both altimetric and GPS altitudes informations in the log. They advize us to turn barometric capsule off to have less noize in the log.



I know exactly what you are saying and dependig on the GPS receiver, there may be what is known as an "auto calibration" mode that the GPS uses to update that barometric information and thus can give an elevation that is different than what is calibrated on the ground initialy,even from a known elevation survey marker. Usually this error will be greater than the manualy calibrated 10 feet tolerance. From the Garmin website:

"The barometric altimiter allows the user to track recent changes in ambient air pressure. This allows the unit to calculate a precise altitude reading when properly calibrated.The barometer, which is responsible for altimeter readings, is not temperature compensated. Temperature changes in the measuring device will affect the barometer and altimeter readings, but these readings will remain within the stated accuracy for the device, approximately 10 feet with proper calibration by the user and slightly higher when using automatic GPS calibration"


Which is why, depending on the model of GPS receiver, it is better to turn off the "auto calibration" and change the "variable elevation mode" to "fixed elevation mode" to give a more consistant and precise elevation reading.When you compare the elevation data logged in these different modes it is clearly visable that the jumps in the readings comes from the GPS adjusted altitude. When you turn off the auto calibration and switch to fixed elevation mode the readings become consistant with the ambient pressure readings.

However,A barometric altimeter uses the atmospheric pressure to determine your altitude above sea level. It turns out they are able to determine altitude within +/- 3 vertical meters or so. The altimeter will detect your change in altitude based on the change in the atmospheric pressure (the higher you go the less pressure).

The problem with a barometric altimeter is the requirement to calibrate it every time you start your activity. If you don't the altimeter will still work and relative measurements will be accurate, but absolute measurements will be off. This means that your cumulative elevation gain/loss will probably be correct, but all of the elevations along the way will be offset by the difference of the actual altitude and the altitude on the device.

GPS altitude doesn't need any calibration, but for complex reasons the GPS unit is not able to determine elevation as accurately as a barometric altimeter.

Combining both GPS and barometric altimeters, Garmin GPS units are able to provide the most accurate altitude readings of any handheld device. Absolute location is provided originally by the satellite to help auto-calibrate the barometric altimeter, then the barometric altimeter is used to provide a more stable elevation change. The GPS device will constantly calibrate the barometric altimeter throughout an activity because the pressure may change due to weather conditions.


The solution to this double sided dilemia is that the barometric altimeter IS more accurate than the GPS adjusted altitude only if the unit is set up and calibrated correctly. In order to do that, with some models of GPS receivers, one has to be familiar with their receiver and turn off the "auto calibration" mode and change the "variable elevation" to "fixed elevation". However, the Foertrex 101/201 and the eTrex vista GPS receivers don't have this feature so there is less of a likely hood for what was discussed here to occur BUT is probably why your GPS technician told you to turn it off or not use a GPS receiver with a barometric altimeter.

Again, if the receiver has a barometric altimeter(which BTW usualy cannot be manualy turned off) the receiver must be calibrated correctly on the ground prior to using it in the sky and will more than likely need to be re-calibrated as the day goes on and the barometric mercury changes.AND, the receiver has to be mounted in a position where it is not likely to be influenced by variations such as turning ones head(even though it is an ideal mounting location). I have found that chest mounting my etrex GPS receiver on my chest strap to give the most consistant readings even though it would seem counter productive to having it there during flight, it simply works(for me). The Foretrex wrist mount is the best of both world for being able to see the sky and for consistant readings as long as one does not move their hand around excessivly during the flight.


A barometric altimeter is what is used in aviation where altitude is an important thing as well as in all the data loggers skydivers commonly use (Neptune/Protrack,etc) because it is an accurate way to determine altitude.
"It's just skydiving..additional drama is not required"
Some people dream about flying, I live my dream
SKYMONKEY PUBLISHING

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Hi people,

multiple wingsuit flyer say on this forum incredible data for his wingsuit-flights without any confirmation.

Dear top wingsuit pilot,
please post your flight data on trackingderby.com. Present yours really performance, bring evidence for all another!

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Hi people,

multiple wingsuit flyer say on this forum incredible data for his wingsuit-flights without any confirmation.

Dear top wingsuit pilot,
please post your flight data on trackingderby.com. Present yours really performance, bring evidence for all another!


Why do you think they would share their secrets?
One secret is a special jump-run where you fly downwind only from exist to deployment.
Hot weather with thermals over your path also can improve your glide.

Don't take it seriously. There is a reason to have a real competition organized.

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Why do you think they would share their secrets?


I speak here about "all hat and no cattle". The GPS-track must be a applicable proof for given declarations.

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One secret is a special jump-run where you fly downwind only from exist to deployment.
Hot weather with thermals over your path also can improve your glide.


Yes, the boundary conditions are important for performance. But good pilot is good pilot...

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There is a reason to have a real competition organized.


Good idea with real competition. All participants jump at more or less same boundary conditions. You can visit e.g. "Wings over Marl", "Wings over Gransee" and verify yours skills :)

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Is it an unfair advantage if you can fly just downwind from exit?



You can do it too. Of course, it is nice to fly all time with downwind ;)

But, in Germany for example, we have restriction for the exit point (2 miles from landing area) and I can't fly all track with downwind, sooner one arc with different alignment to downwind.

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Is it an unfair advantage if you can fly just downwind from exit?



You can do it too. Of course, it is nice to fly all time with downwind ;)

But, in Germany for example, we have restriction for the exit point (2 miles from landing area) and I can't fly all track with downwind, sooner one arc with different alignment to downwind.


We have only fuel/flight time of the plane constraints here. We are not welcomed to stay in the plane minutes after the last jumper exited.

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