GPS data on normal jumps (wishful thinking)

[dthames 0]

I am an avid user of the Flysight device which functions as a 3D position recorder and as a real time feedback device. Outside of wingsuiting and swooping, the Flysight has little normal use in skydiving, today. I hope to see the day that everyone would have a GPS record of every jump. Many of you may not see any benefit at this time, but consider questions about horizontal movement and being able to actually see where group One went and where group Two went, relative to each other both in space and in time. Consider, where did that student actually set up, fly, and turn for his/her landing. Did the wingsuiter/tracker fly back towards the jump run? You couldn't make it back to the DZ, but do you really know where you got out of the plane?

There have been several times in the past year or so when a question would come up and I would like to say, “Show me your GPS track and I will show you mine.” Maybe we will get there someday.

Instructor quote, “What's weird is that you're older than my dad!”

[Lawndarter 3]

dthames

I am an avid user of the Flysight device which functions as a 3D position recorder and as a real time feedback device. Outside of wingsuiting and swooping, the Flysight has little normal use in skydiving, today. I hope to see the day that everyone would have a GPS record of every jump. Many of you may not see any benefit at this time, but consider questions about horizontal movement and being able to actually see where group One went and where group Two went, relative to each other both in space and in time. Consider, where did that student actually set up, fly, and turn for his/her landing. Did the wingsuiter/tracker fly back towards the jump run? You couldn't make it back to the DZ, but do you really know where you got out of the plane?

There have been several times in the past year or so when a question would come up and I would like to say, “Show me your GPS track and I will show you mine.” Maybe we will get there someday.

I have a Garmin ForeTrex 401 I've used for exactly this purpose, or at least, I have taken it up for that a few times. You can export the tracks to Google Earth, but as yet I haven't figured out how to be able to use the altitude data, it just shows the track as 2-D. I'm sure there is a way to get more data from it, I just haven't found it.

[Crispy. 0]

This is one of the reasons I just bought and mounted a Flysight on my helmet. I definitely want to use it for canopy progression (and maybe wingsuting when I get into that), but I also hope to gain some valuable insight into my free fall movement.

[CrashProne 4]

The latest small action cam's are getting GPS now, maybe the day you are talking about isn't that far off?

[sammielu 3]

I wear my flysight for every jump (except CRW).

It's given me peace of mind when I'm worried I pulled low or my pc or canopy sniveled "forever" - knowing that my version of "forever" is always less than 2 seconds feels great. Its also a way to correct my perception when I think I did X under canopy that used up Y feet of altitude... but I really did a crappy/half-assed X and it didn't work as well.

[kallend 1,654]

I wonder if its determination of fall rate is more accurate than a barometric skydiving altimeter. The standard altimeters give wildly varying results based on things like body position, altimeter location, and other factors such as helmet design for in-helmet audibles. Two skydivers falling together in a formation can see quite different fall rate values from their altimeters.

...

The only sure way to survive a canopy collision is not to have one.

[CrashProne 4]

Unfortunately, while GPS is good at many things, accurately determining vertical speed is not generally one of them.

[FlyingRhenquest 1]

I've taken my Flysight on many a regular skydive. I have some code and libraries on GitHub, in my repos. See the gpx2kml, coordinates, time and data libraries, specifically. The Flysight is incredibly accurate as long as you turn it on in the morning for a few minutes, and then again a few minutes before your first jump so it can pull the GPS satellite ephemeris from the satellites.

gpx2kml generates a KML data file which can be viewed on Google Earth or anything else that can read KML. I originally wrote it to take a gpx file from the android "MyTracks" app, which was the first thing I started to experiment with. I thought to take my phone with me on each jump, with MyTracks recording, so that I could see where I was on the map. The code does a pretty good job of detecting when you deploy your canopy, although I never got around to implementing exit and landing detection. The phone's GPS sampling turned out to be entirely inadequate, often losing some or all of each jump and always having some data points out of place or missing entirely.

The Flysight, on the other hand, appears to have no such problems. I get very accurate reads from it on every single jump. If you could access its data in real time, I have no doubt you could make an altimeter from it, although I'm not sure I'd trust my programming or the GPS system quite that far. I have encountered circumstances where my Neptune has been fooled by some maneuver or other performed by the pilot and gone into freefall or under canopy mode briefly. No software is perfect, you just need to understand very well what its limitations are.

Anywhoo, all my code is licensed under Apache's license, so it'd be pretty easy for me or someone else to implement code to shovel a bunch of jumps into a program and spit out a bunch of KML. I mostly haven't because the extra gear it involves is usually more than I want to mess with. If you could just turn tracking on for a device you can carry with you and then do your jumps for the day, it wouldn't be a hassle, but the Flysight's limited battery and a phone's limited accuracy make that difficult.

I'm trying to teach myself how to set things on fire with my mind. Hey... is it hot in here?

[Lawndarter 3]

CrashProne

Unfortunately, while GPS is good at many things, accurately determining vertical speed is not generally one of them.

My Foretrex will display glide ratio and seems to calculate fast, and the tracks are pretty accurate, but it comes down to how often it makes the calculations. Flysights are specifically designed to gather the data very quickly. The Foretrex a bit less so - it has an altimeter but its refresh rate is much slower, too slow to use for that purpose - and it's also only ASL, not AGL.

[dthames 0]

kallend

I wonder if its determination of fall rate is more accurate than a barometric skydiving altimeter. The standard altimeters give wildly varying results based on things like body position, altimeter location, and other factors such as helmet design for in-helmet audibles. Two skydivers falling together in a formation can see quite different fall rate values from their altimeters.

John, I think the vertical speed data is pretty good. Turn on Closed Caption and you can see both the wingsuit speed and the canopy pilot speed (from the GPS data) on this XRW jump. When we are close together the vertical MPH is pretty close to the same. https://youtu.be/xe1rEhUU5Sc

Instructor quote, “What's weird is that you're older than my dad!”

[platypii 20]

GPS is generally more accurate horizontally than vertically. This is because, for the most part, the satellites are not directly above, they are more off on the horizon, and so it is harder to get accurate vertical position.

However, the FlySight actually has an advantage when it comes to fall rate: it can use doppler shift to measure velocity, which can be far more accurate than trying to compute velocity from position.

That being said, I've studied a lot about barometric altitude vs GPS altitude, and looked at a LOT of data. When GPS has a good lock, and comes from a high sample rate, it is usually better. But sometimes it goes wildly off the charts, or fails to update altitude information for a period of time. Barometric altitude has much more variation, and oscillation, based on local pressure differences. But the magnitude of the error is much smaller than the errors you can get from GPS.

If I were setting up for a swoop, I'd feel much more confident going on barometric altitude than GPS. For analysis on the ground, if the data looks clean, I would stick with the GPS data.

BASEline - Wingsuit Flight Computer

[kallend 1,654]

platypii

GPS is generally more accurate horizontally than vertically. This is because, for the most part, the satellites are not directly above, they are more off on the horizon, and so it is harder to get accurate vertical position.

However, the FlySight actually has an advantage when it comes to fall rate: it can use doppler shift to measure velocity, which can be far more accurate than trying to compute velocity from position.

That being said, I've studied a lot about barometric altitude vs GPS altitude, and looked at a LOT of data. When GPS has a good lock, and comes from a high sample rate, it is usually better. But sometimes it goes wildly off the charts, or fails to update altitude information for a period of time. Barometric altitude has much more variation, and oscillation, based on local pressure differences. But the magnitude of the error is much smaller than the errors you can get from GPS.

If I were setting up for a swoop, I'd feel much more confident going on barometric altitude than GPS. For analysis on the ground, if the data looks clean, I would stick with the GPS data.

I was thinking of RW bigways, where the organizer asks "How was the fall rate on that jump?" and you get answers all over the place from various peoples' Protracks, Neptunes, Altitracks, etc.

...

The only sure way to survive a canopy collision is not to have one.

[voyteck 0]

Does tracking for efficiency qualify as a normal jump? I wonder how much useful info I could get from the real time feedback feature of Flysight during a 0.8-1.0:1 track. I will definitely hit that brand new variable-angle horizontal wind tunnel some day in the future when I can afford it but first I would like to give Flysight a try.

[timrf79 0]

Sicne i got my FlySight I usdae it as a logger on every jump with Paralog.
As I am working my way into swooping I often look back at the data and pair it with video to determine the altitude loss on 90's, etc...

I also use the FlySight to evaluate the quality of my track, especially on Trackjumps.

When teaching a canopy course I use it to review the position at which students set up the landing pattern, etc. Paired with Video