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crwper last won the day on June 11

crwper had the most liked content!

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  1. crwper

    Flysight vs GoPro

    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. crwper

    Flysight vs GoPro

    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. crwper

    Flysight vs GoPro

    Looking at the JSON file, it does seem to be a direct dump of the GPMF data embedded in the MP4. Here's a collapsed view of what's in the file which shows the headers but not the data itself: Looking at the "GPS5" key, it seems to include only 5 values: latitude longitude altitude 2D speed 3D speed In addition, nested in the GPS5 data, it occasionally includes two more pieces of information: "fix" - This seems to be the GNSS fix type (3 for 3D, 2 for 2D, etc.). "precision" - If I had to guess, I'd say this is position accuracy in cm. That's not too bad. There are a couple of things missing compared to FlySight's data: Components of 3D velocity. In principle you can recover the vertical component from 3D speed and 2D speed, but there's no way to get north and east speed directly from this data. You would have to go through latitude and longitude, which will likely result in some additional error. Components of accuracy. FlySight includes horizontal and vertical position accuracy as well as speed accuracy. Number of satellites used in the fix. This can be a useful diagnostic, but there is arguably some overlap with the position accuracy figure reported in the GPMF data. I suspect at 18 Hz this is GPS only, for the reasons given above, but it may be that if you drop down to 10 Hz the unit will automatically switch over to GPS + GLONASS. Here's the relevant table from the u-blox M8 datasheet: Assuming their velocity is coming from the same place FlySight's is, I feel like the GoPro data would be just fine for most uses.
  4. crwper

    Flysight vs GoPro

    It sounds like you might be looking at the <sat> field in the GPX file, which actually gives the fix time--i.e., 2D or 3D--so it typically has a value of 2 or 3. The minimum number of satellites required for a GNSS fix is 4, so if you're seeing a value of 3, it's definitely not the number of satellites used in the fix. Can you post an example of the GPX data produced by the GoPro? It looks like the <sat> field in the GPX file would give the number of satellites used in the fix.
  5. crwper

    Flysight vs GoPro

    It's been a while since I checked the forums, but I came across this post and thought I'd add a little more information. The latest FlySight hardware uses the NEO-M8Q module, which supports 10 Hz update while tracking both GPS and GLONASS satellites, or 18 Hz while tracking a single GNSS constellation. There's nothing magical about 18 Hz, so I think the GoPro is probably also using a u-blox M8 chip. The main limitation with the latest FlySight hardware is processor speed. I haven't checked to see if we can run at 18 Hz, but it might be possible, especially if we disable audio output. However, I would say that we've seen some really good results with GPS + GLONASS tracking. Roughly speaking, this doubles the number of satellites in view, which makes the fix a little more accurate and a lot more robust. If I had to choose, I would probably go with 10 Hz and two constellations as opposed to 18 Hz and GPS only. My guess is that the GoPro is using GPS only at 18 Hz. This could be confirmed by looking at the number of satellites used in the fix (assuming this is reported). If you see a number around 8-12, it's likely GPS only. If you see a number more like 12-18, it's probably tracking GPS and GLONASS. There is one other thing I would pay close attention to. One of the things I like most about the u-blox module inside the FlySight is that it reports 3D velocity, so there is no need to calculate velocity from differences in position (which is notoriously error prone). This may very well be the same interface that the GoPro uses, but it's very common for consumer GPS units to use the NMEA interface instead. This is an old interface which doesn't have native support for 3D velocity, which means vertical speed needs to be calculated from differences in elevation. You can probably tell which method GoPro is using by looking specifically at vertical speed. How clean are the measurements? If you hold the GoPro in your hand and wave it over your head, up and down, etc., do you see clean velocity measurements on all three axes (even though position may not reflect that motion)?
  6. crwper

    gary connery without a rig

    Spot on, I'd say. It's hard to say what effect removing the rig would have on the aerodynamics of the suit. With all his pre-jump preparation being with the rig, I think it would be foolish suddenly to remove it for the big jump. Michael
  7. crwper

    Flysight GPS Actual use feedback

    This is a particularly interesting subject for me. My interest in real-time feedback has been inspired partly by technology like this which helps people who have lost their sense of balance. Devices like the Brainport stimulate the user's tongue to tell them when they're leaning to one side. The brain can use this information, in lieu of a normal sense of balance, to remain upright. Perhaps even more interestingly, research has shown that, the longer something like this is used, the longer the patient can actually go without it. The brain isn't just using the device as a crutch, but is actually figuring out what else indicates an off-balance position. This sort of learning really only works with immediate feedback. If you look at data after a jump, you'll get a conscious idea of how well you did--still a valuable thing to know--but it doesn't really help your brain learn the way immediate feedback does. My hope with FlySight is that, given immediate feedback, our brains will actually pick up on cues that we wouldn't necessarily have noticed on our own--things like the sound of the air going by, the feeling of being tipped slightly forward, or the sensation of pressure on the chest. With time, I think these things will begin to form a sense of glide ratio.
  8. These pages should do it for you. First, the LANC pinout: Next, the pinout for the Sony 10-pin connector (the half-moon connector): You'll need to wire pins 2, 3, and 4 from the half-moon connector to pins 1, 3, and 2 of the 2.5 mm jack. Michael P.S. If this helps, I could sure use a photo of the LED end of the CamEye, as mentioned in this thread: Thanks! P.P.S. Looking at the 10-pin connector pinout, I just realized you may also need to pull pin 7 to ground through a 100k resistor, in order to activate the LANC interface. P.P.P.S. I also just realized your half-moon connector has only 6 wires coming from it. I'm guessing they might be breaking out only the A/V pins (i.e. everything but the 4 LANC-related pins). If this is the case, the connector you have isn't going to cut it. It might be best to purchase an adaptor cable like this one:
  9. crwper

    120' S

    I don't keep track of everything, but almost all of my static line jumps are in winter, with temperatures around -10 Celsius. The 111' span is at an elevation of about 3500' ASL; the 165' and 140' jumps are at about 2500' ASL. Most of my s/l jumps are from the latter object. Unfortunately, because there isn't much variation in the conditions I've jumped it in, I can't really quantify the effect of temperature/barometric changes. I've usually used shallow brake settings on s/l jumps. This seems to reduce surge when the brakes are released. It's a bit of a balance, though, since a too-shallow setting will result in a lot of surge before the brakes are released. Too-deep will put the canopy closer to a stall on opening, and encourage a surge after the brakes are released. Michael
  10. crwper


    Dave: As 980 pointed out, there are two sides to the loop, so it breaks at about 160 lb. My understanding is thus: If you put 80 lb of tension on the cord, that's 80 lb per side, which means the total force between the anchor and the bridle is 160 lb. For the knot, use a surgeon's knot. Back it up with as many overhand knots as you like. Vincent: The bridle attachment point is much stronger than a loop of break cord. It's a good idea to check the attachment point regularly regardless of what kind of jumping you do, but unless something unusual is happening, there should be no problems. I have done one static line jump with no pilot chute. We were jumping a 111-foot span and the canopy barely had time to fly. I thought if I removed the PC, it might help, and also thought it couldn't really be much of a backup from that height. There was no measurable difference in canopy flight between jumps with/without the pilot chute. DW later pointed out that the most likely time to get a premature break is actually fairly late in the deployment sequence, and there is a good chance that a 48" pilot chute would help even on very low jumps. So I don't think there's any reason to jump without one. Michael
  11. crwper

    crosswinds and offheadings...

    Now that's a disturbing photo. Here's something I've never thought of before: Suppose the crosswind is from the left. You jump, you pitch. The PC moves to the right slowly as it pulls your canopy out. By the time your canopy is nearing line stretch, the line from you, through your canopy, and to the PC is angled to the right. Now, take that line, and imagine how your canopy sits on it. Looking from the front, you see the exposed nose of the canopy, and the whole packjob is kind of cockeyed, tilted to the side the PC is pulling from. The natural tendency of the packjob will be to slump toward the bottom side of the line. From the jumper's point of view, that means it's going to swing so that the nose faces left. The risers aren't even loaded, and already your packjob is 90-left. I suspect this effect is independent of whether or not you have a Multi. At this point, the Multi is still closed. Another interesting thing is that this won't happen every time. It's possible you will get lucky and your packjob will be relatively well-balanced on the line. In that case, it may not rotate at all before it begins to inflate (at which point it becomes much more stable in regards to this kind of thing). But it means that crosswinds are a bit of a crap shoot, which I think we all know from experience. Michael
  12. crwper


    I think you're going to have to be a lot more specific about: 1. What kind of gear you're jumping. 2. What you're doing. 3. What's not working. Michael
  13. crwper

    riser hardware?

    Looking at Paragear, it seems to be a "number 10 style ring", but I think more people would know it as the big ring in a set of 3-rings. Michael Edited to clarify the link
  14. crwper

    Thinking about BASE

    I'm assuming here you have not done a lot of platform diving. If you have, well, you're one step ahead of me. If you can find a pool with a 5-metre platform (not a diving board), then just practice jumping off it. You don't have to do a BASE exit. (1) Try stepping off first, since that's easiest. (2) Then try launching hard from the edge, and land in the water feet first. How hard can you launch? (3) Try running off the end. Don't pace it out, just go to the back of the platform and run for it. Jump when you have no more steps left. (4) Try sideways and rear-facing "exits". (5) Try just hucking yourself off and sorting the rest out in the air. You have about a second. The general idea of all this is that you have an innate monkey-sense which lets you leap off one thing and ensure you're in a particular position when you land. We don't use it often, but it's there. Jumping from the 5-metre platform will build your confidence in that sense, so that when you do your first BASE jump, you won't have to rely on "head up, chest forward". You may also learn some other things along the way. I learned that if I do a positive launch, as opposed to stepping off, I am much more aware of my time in freefall. I also learned how to do a good running exit, without over-thinking it. A lot of others have said this already, but take your time getting into BASE. When it goes well it's fabulous, and this is what you see most of the time. But it can also be incredibly brutal. When it goes badly, it can go very, very badly. Michael
  15. crwper

    Body Armour

    I wear a Dainese Shuttle Pro suit on every jump. Never had a problem with freedom of movement due to the armour. Michael