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danielvelez
Falchetto
Colombia
145 Posts |
 Posted - 02/04/2018 : 04:01:42
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Ok. I´m aware that livetracking is a work in progress and that there´s too much to consider. I have had the opportunity to fly to few times with some friends that are sharing their location using livetrack24. I´m using android phone and lk 6.1r.
The but that I´m guessing is happening, is related to missinterpretation of height. My lk8000 sets an automatic qnh before taking off (really handy but sometimes buggy for hanggliders and/or paragliders, as terrain mesh with 1 arc deg right on the edge of a takeoff can represent +/- 50mts height difference) So my calculations are made considering that QNH setting. Eventhough, I´m pretty sure (but guessing) that the livetrack feedback as same as the igc logfile are stored with standard 1013.25 QNE. That means that your friend will be reporting his position with QNE and you will be flying with QNH, so your computer will put him off and will report him off when he is actually at your same height.
I´m still on the need to double check this, but the few times that I have flown with friends they appear to be "off" by 100mts sometimes. Not sure if livetrack uses GPS height...
So the way for hard testing would be to use two devices on the same glider running lk8000 and livetracking to each other, and adjusting one of the QNH at least 100mts off the QNE, and the other to QNH = QNE. If there´s an actual bug, then one device will show the 100 mts difference and the other would see no difference (no significant difference).
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Edited by - AlphaLima on 04/05/2018 18:23:06 |
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ToninoTarsi
Falchetto
Italy
113 Posts |
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danielvelez
Falchetto
Colombia
145 Posts |
Posted - 05/04/2018 : 05:29:27
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quote:
Originally posted by ToninoTarsi
The LiveTracker uses "NavAltitude" that is QNH altitude.
Tony
Ok. I made some photo tests...
https://photos.app.goo.gl/E5yCne5mcmgM1wgO2
Help me out here. Please read description on each picture (info) to see what you are looking at.
Even when the devices are next to each other, and they show same height (using Baro altitude in QNH), they see each other appart on the same ammount that the "QNH" deviates from the "QNE" or the "GPS Height". On one of the pictures you could read 1449 mts on both baro altimeters, but one device says that the other is 170 mts below and same with the other so both think that the other pilot is below...
It´s like my airplane position on the FLARM screen takes 1013.25 or GPS, and reads QNH from the other planes (1008).
If I go to "Nav by HGPS", ignoring the Baro, then the height matches and the flarm display is also coherent with that.
Now there is a more strange picture: The last one, where I show what happens if one device has Barometric readings adjusted 100 mts above gps height and the other device is using gps height...
The device that is using Baro, reads the GPS height of the other and compares it to his own GPS or 1013 height, so they match on the FLARM, even when their reported altitude reading is 100 mts off... But the pilot with gps height will read the "Barometric QNH" of the other pilot and put him 100 above, acording to the difference in the "alt readings".
I think there´s a "bug". Not sure how to deal with it... probably using GPS for livetracking, or going to standard 1013... As QNH could lead to pilots crashing when the QNH differs to the QNE or the GPS.
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ToninoTarsi
Falchetto
Italy
113 Posts |
Posted - 05/04/2018 : 10:36:37
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quote:
As QNH could lead to pilots crashing when the QNH differs to the QNE or the GPS.
Obviously LiveTrack24 Radar is ABSOLUTELY NOT INTENDED as an anti-collision system but only as an information system that gives APPROXIMATELY the position of your friends and I find it very useful during my flights to have a rough idea where my friends are.
As data are updated every 5 seconds an error of more than 100-200 meters (in HG/PG and even more in GL) is absolutely normal (and this not taking into account network lags)
So ... maybe your point is correct but beyond the scope of the instrument. Anyway I will check your point and if there is a systematic error I will try to fix it but do not try to use it with such a precision ... for this maybe you can use a real FLARM system like AirWhere for PG/HG
Tony
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www.VoloLiberoMonteCucco.it |
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danielvelez
Falchetto
Colombia
145 Posts |
Posted - 05/04/2018 : 23:10:43
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quote:
for this maybe you can use a real FLARM system like AirWhere for PG/HG
Tony
I´m looking forward to the Airwhere system and will probably order some modules to start playing with it sometime soon.
Still, I would guess that the strange behaviour will be present with a "REAL" FLARM, or an Airwhere system, as the sent data would be QNH bur compared internally to a "QNE" or "GPS" data... So two pilots sending FLARM or Airwhere data at the same QNH height but with a QNH calibrated higher or lower than the QNE, will be shown faster and more relyable on the lk8000 radar, but consistently higher or lower at the same time on both devices...
I will take more than 3 months to verify this (as i need to put up an order for airwhere, then wait for the parts to arrive, then figure out if I´m man enought to make them work as supposed).
:)
Anyway, thanks for taking the time to look up into this. |
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Livetrack24 feeding (NOBUG)