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Showing content with the highest reputation on 06/11/2019 in all areas

  1. 1 point
    Some of the advanced analysis features in FlySight Viewer use the full 3D velocity vector. For example, you can use this to estimate lift and drag forces. The N/E components are also used to determine wind speed/direction using data from the climb to altitude.
  2. 1 point
    As @platypii points out, in general deriving velocity from changes in position is a bad idea. This is known as the method of "finite differences" and is a notoriously error-prone way to calculate derivatives. That said, you may find this works better than expected with FlySight data (or GoPro data if they are using a similar chipset), since both the position and velocity are outputs of the same Kalman filter--so the smoothing @platypii refers to may already have been done inside the GNSS module.
  3. 1 point
  4. 1 point
    I dont think that this thread is an accurate representation of the general community. Most modern skydivers when asked at the DZ would probably dismiss skydiving as not being that dangerous. I've asked. Many times. I rarely have a skydiver tell me that they do in fact believe that skydiving is dangerous. Nearly every conversation I've ever heard about skydiving risk results in most of the participants dismissing it as being a fairly safe activity. I recall where someone I know was seriously injured from landing a malfunctioning canopy and his very first post on Facebook once he recovered was him trying to reassure his friends that skydiving is in fact safe and his friends should not worry.
  5. 1 point
    Started jumping in 2002, on average I would say one funeral every 2 to 3 years. I do not believe our local safety record is worse than average, or worse than that of the US. I would be surprised if my experience is extreme compared to others who have been jumping for ~ 17 years. The point is, I keep hearing about other dangerous stuff - driving to the dropzone, driving to work, riding a motorcycle, scuba diving.... The fact is, I know a lot of people who participate in those (probably more than I know skydivers) , yet I have never been to a funeral for one of those. I do understand that some of you have, but again, I would be surprised if that number is anywhere near as high. Asking if skydiving is "safe" is mostly a matter of how much risk you find acceptable.
  6. 1 point
    What canopy are you jumping? Size and type. How big of groups are you jumping? How good are you at tracking? Since you are fairly new, I'm guessing you are jumping a reasonably big, docile canopy. If you are jumping a sub-100 cross-brace, there are other issues that are more important than your packing. For something that won't point you at the ground and spin you into unconsciousness, the problem with line twists is that you can't maneuver until you are out of them. So if you are jumping in bigger groups, where traffic issues may be present immediately after opening, or if you can't track well enough to get good separation, then line twists can be a very real problem. There's a whole laundry list of issues that may cause line twists. Most of them involve symmetry. Make sure your risers are even when you start. Some folks tie the big rings together with a pull up cord to make sure. Make sure your line stows are even. If they are uneven, the bag can twist as it goes to line stretch. Maybe stow the lines like you usually do and then pull them out. Pull with the bridle. See if the bag does anything odd. Make sure the nose is as symmetrical as you can. If one side inflates faster, that can induce twists. Same goes for wrapping and cocooning it. You might want to find a packer who is willing to watch you pack. See if they can spot any issues. The best time to do this would be the end of the day, and make sure you have some beer to offer ("hey, can you watch me pack to see if I'm doing anything obviously wrong? I have a couple beers you can drink while you watch")
  7. 1 point
    How about using two audibles (Solo II or something like that) and no visual altimeter at all during freefall? So just a wrist-mounted altimeter for canopy ride?
  8. 1 point
    Computing velocity from noisy position data can introduce a fair amount of error. Here is an example. Your true velocity might be constant and actually look like: But GPS will have errors that might make the position look like any of the black dots here, and you can see how much error that can introduce to the velocity if computed using distance / time: It's possible to smooth this out by adding a Kalman Filter. But a filter will introduce its own errors and create a lag time before it accurately estimates your true velocity. However, as pointed out by @crwper, GPS actually has the ability to compute position directly, not using position and distance. Instead, many GPS chips can actually use doppler shift from the satellites to directly compute velocity. The accuracy and response time is much better. It is not clear whether the GoPro uses doppler velocity to compute 2D and 3D speed, but its definitely NOT giving the individual velocity components (vN, vE, vD) which would be nice to have.
  9. 1 point
    I figured I should make my own parser to output a CSV similar to that of a Flysight, so here goes : https://github.com/j-allison/gopro-to-flysight Before (using data from the util cited above: https://tailorandwayne.com/gopro-telemetry-extractor/) : After using my parser, based on `gpmf-extract` and `gopro-telemetry` libraries: I'm feeling happier with those results; they seem to be way less "smoothed out". Still work in progress. (Is it outrageously wrong to calculate N/E velocity components by using lat or long difference over time difference from point A to point B ? )