crwper 7 #1 May 8, 2006 Hi all, For the past year I have been developing an audible glide-angle indicator. The system is built from a wireless Garmin GPS 10, a Palm Tungsten T, and a pair of ER-6i earphones. I've written software for the Palm which takes velocity data from the GPS and calculates glide angle. This is converted to a series of beeps. Better glide angle corresponds with a higher rate and pitch for the beeps (like a vario). I have not yet had a chance to test the software on a skydive, but hope to do so soon. The biggest hurdle I can think of at the moment is minimizing the time to first fix when I leave the aircraft. The fact that some of you are getting good GPS tracks on your skydives makes me think you may have some tips here. How do you minimize the time to first fix? Michael P.S. Incidentally, I will be making the software (and source code) freely available very soon. Right now it would only be useful to those with a similar setup to my own. If you would be interested in playing with something like this, please let me know what equipment you're using, and I'll do what I can to make sure it's supported. Quote Share this post Link to post Share on other sites
dragon2 2 #2 May 8, 2006 Does that palm contain a harddrive? If it's solid state memory you're good to go but if it has a harddrive/microdrive it'll get damaged when skydiving. ciel bleu, Saskia Quote Share this post Link to post Share on other sites
Gadget 0 #3 May 8, 2006 Palm is solid state memory and sd cards.So no problem with that.If people from Poland are called Poles, why aren't people from Holland called Holes??? My logbook Quote Share this post Link to post Share on other sites
phoenixlpr 0 #4 May 8, 2006 More simple: hard drives are designed to work on gound level, normal air pressure, not for 4000m and they don't like to be dropped either. Quote Share this post Link to post Share on other sites
cpoxon 0 #5 May 8, 2006 QuoteHow do you minimize the time to first fix? Install a GPS signal repeater inside the aircraft?Skydiving Fatalities - Cease not to learn 'til thou cease to live Quote Share this post Link to post Share on other sites
Zoter 0 #6 May 8, 2006 I remember watching Costyn doing a funny walk on jump run to make sure his GPS unit was as close to and as high as possible to every window on his way to exit the aircraft... Quote Share this post Link to post Share on other sites
Costyn 1 #7 May 8, 2006 QuoteI remember watching Costyn doing a funny walk on jump run to make sure his GPS unit was as close to and as high as possible to every window on his way to exit the aircraft... Yeah, I try to do that, but it doesn't always work. I usually try to pester the person who's sitting next to the pilot until he relinquishes his seat to me. I get pretty good coverage (8 or 9 meters accuracy) when I'm seated there. As long as you are not seated beneath the wing the gps will find a couple satellites it can latch on to. So sitting in the back near the door (of a caravan or twin otter) will work too. I've found that the shorter the interruption of signal is to the GPS unit, the longer it takes to re-acquire (up to a max of 15 seconds). If the pilot is dropping you a little further out on a wingsuit jump you can sit next to the door and have the GPS look at the sky through there while you wait for the pilot to travel his 3 NM from the dz. Anyways, crwper thats a really interesting setup. I've been thinking about something simllar too. I haven't done much research, but I figure I should be able to find a PDA with a headphones jack and a USB or serial port (any suggestions??). That would be the hardest part. Writing the software isn't too hard is it? Cheers, Costyn.Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News Quote Share this post Link to post Share on other sites
LouDiamond 1 #8 May 8, 2006 QuoteThe biggest hurdle I can think of at the moment is minimizing the time to first fix when I leave the aircraft. Actually there are a series of things you can do to make this easier to accomplish. The most important is to turn the GPS receiver on while on the ground and allow it to accquire at least 4 satellites and receive new almanac data. This will ensure the receiver has the latest sat data and "knows" where to look for the sats when you turn it back on. Prior to boarding the aircraft, turn the receiver back on. You may or may not start logging data during the Aircraft climb, depending on your reception but its not a big deal as you can trim that data off in post processing. As was mentioned, a GPS signal repeater can be used. Depending on which one you use, it will either run on batteries or have a cigarette adapter power cord. Both, will require you to mount it probably in the cockpit area where it has a good view of the sky, so plan on coordinating with the pilot and installing it before the props are spinning. The easier way is to try to allow it to see a portion of the sky during the climb just so that you will have either a warm or hot start when you move to the door after the last skydiver leaves. The time you spend by/in the door should allow you enough time to reaccquire enough sats to get a 3D lock before leaving the aircraft. It is not uncommon to see some weird speed readings around the exit point later on in post processing. The type of GPS receiver you use and where you have it mounted also play a significant part in accquiring sats. For helmet mounts, look at www.ram-mounts.com for GPS specific mounts and ideas."It's just skydiving..additional drama is not required" Some people dream about flying, I live my dream SKYMONKEY PUBLISHING Quote Share this post Link to post Share on other sites
crwper 7 #9 May 8, 2006 QuoteI haven't done much research, but I figure I should be able to find a PDA with a headphones jack and a USB or serial port (any suggestions??). First, in-ear earphones like the ER's are a must. I tried this last year with a regular set of earphones and a home-built amp, but it really is easy to forget how loud freefall is, isn't it? Second, go with wireless if you can. Last year I had a Garmin Geko hooked up through the universal connector on the Palm. I'd get the thing working, and then without fail on jump run it would come undone. Wires are a major pain. Bluetooth on the Palm is just another serial port. QuoteWriting the software isn't too hard is it? It is, and it isn't. Michael Quote Share this post Link to post Share on other sites
crwper 7 #10 May 8, 2006 QuoteInstall a GPS signal repeater inside the aircraft? Are you serious about this? Somehow I've always thought of GPS repeaters as an expensive setup for tradeshows. If there's an inexpensive repeater, well, that might just be fun. Michael Quote Share this post Link to post Share on other sites
Costyn 1 #11 May 8, 2006 QuoteFirst, in-ear earphones like the ER's are a must. I tried this last year with a regular set of earphones and a home-built amp, but it really is easy to forget how loud freefall is, isn't it? Yeah, it is loud. I took my ipod mini up once, and I could hear it ok with my earphones (Sony MDR-EX71LP) during freefall. I later learnt this was really stupid (could've crashed the harddrive), but I guess I was lucky. QuoteSecond, go with wireless if you can. Last year I had a Garmin Geko hooked up through the universal connector on the Palm. I'd get the thing working, and then without fail on jump run it would come undone. Wires are a major pain. Bluetooth on the Palm is just another serial port. I would like to go wireless, but I'm not gonna go out and buy another GPS just because it has wireless. QuoteIt is, and it isn't. Yeah programming for a platform for the first time is pretty tough. Especially if you're trying something ambitious. I haven't done any Palm programming either, but extracting information out of 2 coordinates and an elevation was actually pretty easy when I was writing my script. But I guess the calculations aren't the hard part.Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News Quote Share this post Link to post Share on other sites
crwper 7 #12 May 8, 2006 QuoteYeah, it is loud. I took my ipod mini up once, and I could hear it ok with my earphones (Sony MDR-EX71LP) during freefall. This is great news. I've tested the ER's in other circumstances with amazing results, but haven't actually had a chance to test them in freefall. The Sony's are also an excellent choice. QuoteI would like to go wireless, but I'm not gonna go out and buy another GPS just because it has wireless. It does. One of the features I really like is that the GPS 10 sends a proprietary Garmin "NMEA" sentence that contains 3D velocity information accurate to 0.1 knots. I've been assuming this was calculated from phase data in the GPS hardware, but recently noticed there is a "velocity filter length" setting for the GPS, so it might just be a finite difference on position. Still, testing it in the car it seems very stable and responsive, so I think it will work well in the air. QuoteBut I guess the calculations aren't the hard part. Exactly. Michael Quote Share this post Link to post Share on other sites
agent_lead 0 #13 May 8, 2006 will this software run on windows mobile 5? i have a wm5 device with gps and would love something like this to be aboe to run on my phone-------------------------------------------- www.facebook.com/agentlead Quote Share this post Link to post Share on other sites
crwper 7 #14 May 8, 2006 Quotewill this software run on windows mobile 5? Sorry, Palm only. Michael Quote Share this post Link to post Share on other sites
yuri_base 1 #15 May 8, 2006 Michael, I think the biggest hurdle will be the noisyness of altitude data from barometric GPS. See, for example, this. Vista C, mounted on the helmet, head was not moving much, yet vertical speed data fluctuates as much as 100% (e.g. from 75mph to 38mph) in 1-sec intervals. The beeper will go nuts. How do you plan to fight this problem? YuriAndroid+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
KrisFlyZ 0 #16 May 8, 2006 The Edge 305 has a built in feature that makes it beep if any of the parameters being tracked falls in a certain range or exceeds a threshold. Not sure if Grade is one of the available parameters. Will check.... It does not directly support earphones. Kris. Quote Share this post Link to post Share on other sites
crwper 7 #17 May 8, 2006 QuoteThe beeper will go nuts. How do you plan to fight this problem? I'm going to build in kind of a "cutaway handle". If the altitude data is completely out to lunch, and the beeper is really pissing me off, I'll just pull the cutaway. The whole mess (GPS, PDA, and earphones) will just fall away, and with any luck I'll have forgotten about the whole fiasco by the time I land. This is something I was pretty concerned about when I first started the project. I've done some work with GPS equipment before, and have noticed that finite differences on position don't yield very good results for velocity. This is why I've been under the impression that the GPS 10, which claims 0.1 knots velocity accuracy, uses phase drift from the GPS signal to calculate velocity, rather than finite differences. I'm not sure, though. Michael Quote Share this post Link to post Share on other sites
Costyn 1 #18 May 9, 2006 Quote I've noticed that the GPS altimeter readings are quite accurate on my ForeTrex 201 (it doesn't have a barometric altimeter). There's no wild fluctuations and especially in freefall the unit has a nice clear view of the sky so the 3D readings should be quite accurate. Of course I'm not a GPS expert and can only comment on my experiences. Seeing that TrackingDerby.com also recommends the 201, I'm guessing they came to the same conclusion.Costyn van Dongen - http://www.flylikebrick.com/ - World Wide Wingsuit News Quote Share this post Link to post Share on other sites
yuri_base 1 #19 May 9, 2006 QuoteGPS altimeter readings are quite accurate on my ForeTrex 201 (it doesn't have a barometric altimeter). Does anybody know how to disable barometric altimeter on ETrex Vista C?Android+Wear/iOS/Windows apps: L/D Vario, Smart Altimeter, Rockdrop Pro, Wingsuit FAP iOS only: L/D Magic Windows only: WS Studio Quote Share this post Link to post Share on other sites
