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TouchTheSky
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Group: Forum Members
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+xI had to add corrections for geoid separation and baro pressure. Traffic's real baro pressure might be different if there's a big difference in altitude, but it should be accurate as long as we're on the same level within several hundreds of feet. Yesterday was a good day for testing because my local QNH was about 1018 hPa. All flarm devices on the ground were displayed as on the ground 
Change the altitude block in func processAprsData of /root/stratux/main/flarm.go to this one: // set altitude ti.Alt = int32(data.Altitude) ti.Alt = ti.Alt - int32(mySituation.GPSGeoidSep) // fix geoid sep ti.Alt = ti.Alt - int32(mySituation.GPSAltitudeMSL) + int32(mySituation.BaroPressureAltitude) // calc traffic's baro alt ti.AltIsGNSS = false ti.Last_alt = stratuxClock.Time
So what you are suggesting in summary is to modify the following:
/root/stratux/main/gen_gdl90.go, func makeOwnshipGeometricAltitudeReport()
from: mySituation.GPSAltitudeMSL
to: mySituation.GPSHeightAboveEllipsoid
/root/stratux/main/flarm.go, change the altitude block in func processAprsData
// set altitude
ti.Alt = int32(data.Altitude)
ti.Alt = ti.Alt - int32(mySituation.GPSGeoidSep) // fix geoid sep
ti.Alt = ti.Alt - int32(mySituation.GPSAltitudeMSL) + int32(mySituation.BaroPressureAltitude) // calc traffic's baro alt
ti.AltIsGNSS = false
ti.Last_alt = stratuxClock.Time
These changes are only recommended if FLARM Stratux is used with SkyDemon, right? What about ForeFlight, EasyVFR and Sky-Map?
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neubamat
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Group: Forum Members
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I had to add corrections for geoid separation and baro pressure. Traffic's real baro pressure might be different if there's a big difference in altitude, but it should be accurate as long as we're on the same level within several hundreds of feet. Yesterday was a good day for testing because my local QNH was about 1018 hPa. All flarm devices on the ground were displayed as on the ground
Change the altitude block in func processAprsData of /root/stratux/main/flarm.go to this one: // set altitude ti.Alt = int32(data.Altitude) ti.Alt = ti.Alt - int32(mySituation.GPSGeoidSep) // fix geoid sep ti.Alt = ti.Alt - int32(mySituation.GPSAltitudeMSL) + int32(mySituation.BaroPressureAltitude) // calc traffic's baro alt ti.AltIsGNSS = false ti.Last_alt = stratuxClock.Time
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neubamat
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Group: Forum Members
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+x+xIt looks like there's an issue with the altitude regarding FLARM traffic as well. GDL90 spec (3.5.1.4) defines altitude as pressure altitude, but FLARM traffic contains just GPS alt. There's a flag in the TrafficInfo struct, but it's not converted in the stratux code and send as it is...
Traffic might be off for several hundreds of feet depending on the actual baro diff.
Is there an easy fix available? Probably by shifting the altitude using the difference between gps alt and baro alt from mySituation... Another thing that might lead to differences in altitude is that GeoidSepar isn't set in stratux.conf.template I'll check it on the weekend, when I've got access to FLARM devices with known altitudes again.
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TouchTheSky
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Group: Forum Members
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Visits: 4.4K
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+xIt looks like there's an issue with the altitude regarding FLARM traffic as well. GDL90 spec (3.5.1.4) defines altitude as pressure altitude, but FLARM traffic contains just GPS alt. There's a flag in the TrafficInfo struct, but it's not converted in the stratux code and send as it is...
Traffic might be off for several hundreds of feet depending on the actual baro diff.
Is there an easy fix available?
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neubamat
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Group: Forum Members
Posts: 19,
Visits: 18
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It looks like there's an issue with the altitude regarding FLARM traffic as well. GDL90 spec (3.5.1.4) defines altitude as pressure altitude, but FLARM traffic contains just GPS alt. There's a flag in the TrafficInfo struct, but it's not converted in the stratux code and send as it is...
Traffic might be off for several hundreds of feet depending on the actual baro diff.
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neubamat
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Group: Forum Members
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If somebody is wondering why the altitude using Stratux is a little bit off compared to the GPS altitude (in my case it's 115ft too low), this is the reason:
GDL90 protocol specifies that the geometric alt report contains the altitude above the WGS84 ellipsoid. SkyDemon handles this correctly and computes the MSL altitude. Stratux however sends the MSL altitude already and there's a big thread on the github page because most of the EFBs expect MSL altitude (against the spec).
As a quick fix change the following variable in /root/stratux/main/gen_gdl90.go, func makeOwnshipGeometricAltitudeReport()
and recompile stratux: service stratux stop && cd /root/stratux && make && make install && systemctl daemon-reload && service stratux start
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neubamat
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Group: Forum Members
Posts: 19,
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+xNumber Two - WiFi security should be enabled and maybe the SSID changed:
This simple command does almost the same and you don't need to reboot: sudo hostapd_manager.sh -s YOUR_SSID -p YOUR_PASSWORD
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xray
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Group: Forum Members
Posts: 2,
Visits: 0
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+x+x+xGood news, now there is a ready-to-go Stratux FLARM image available which potentially will be updated on a regular basis:
Congratulations, TTS, right at the first time I visit this forum I find a brand-new solution for open source FLARM application by chance! Unfortunately I'm only an average SD user, and I would like to verify whether I got it right. The configuration You describe has tuned the 978 MHz (US weather etc.) for Europe to FLARM frequency. First question: Can other AC see me with this Stratux modification or can I only see their FLARM–signal on my unit? Is it ADS-B in and out? Second question: I read the whole SD thread, but I am new to github. Means: the link https://github.com/PepperJo/stratux/releases/tag/v1.4r5-flarm is cryptic to me. I think I have to start with a Stratux unit according to stratux.me and modify this in a second step. Could You please guide my mind towards this second step? For other prospective builders too a little tutorial would surely be helpful, and the idea would be worth spreading. I would appreciate it very much. Thanks Richard Richard,
Answer 1: Stratux is not transmitting any signal, unlike PilotAware does. Therefore it is only FLARM in & ADS-B in. Answer 2: You have to start based on a standard Stratux hardware and flash a microSD card with the above mentioned image file.
I will compile a litte tutorial over the next couple of days.
If you don't want to bother with this, I can offer a ready to run version for sale because I have already built a couple of devices for testing. I don't want to make a substantial business out of it (my bill of material per device was roughly € 150,-) but would sell it for € 299,- potentially through eBay. I am also working on a "premium" version with SuperF Antennas for € 349,-
...both ideas are interesting for me. My transponder does not have extended squitter; so it is a pity that Stratux is only ADS-B in.
Surely the FLARM - process is still proprietary. Thanks
Richard
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TouchTheSky
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Group: Forum Members
Posts: 153,
Visits: 4.4K
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+x+xGood news, now there is a ready-to-go Stratux FLARM image available which potentially will be updated on a regular basis:
Congratulations, TTS, right at the first time I visit this forum I find a brand-new solution for open source FLARM application by chance! Unfortunately I'm only an average SD user, and I would like to verify whether I got it right. The configuration You describe has tuned the 978 MHz (US weather etc.) for Europe to FLARM frequency. First question: Can other AC see me with this Stratux modification or can I only see their FLARM–signal on my unit? Is it ADS-B in and out? Second question: I read the whole SD thread, but I am new to github. Means: the link https://github.com/PepperJo/stratux/releases/tag/v1.4r5-flarm is cryptic to me. I think I have to start with a Stratux unit according to stratux.me and modify this in a second step. Could You please guide my mind towards this second step? For other prospective builders too a little tutorial would surely be helpful, and the idea would be worth spreading. I would appreciate it very much. Thanks Richard Richard,
Answer 1: Stratux is not transmitting any signal, unlike PilotAware does. Therefore it is only FLARM in & ADS-B in. Answer 2: You have to start based on a standard Stratux hardware and flash a microSD card with the above mentioned image file.
I will compile a litte tutorial over the next couple of days.
If you don't want to bother with this, I can offer a ready to run version for sale because I have already built a couple of devices for testing. I don't want to make a substantial business out of it (my bill of material per device was roughly € 150,-) but would sell it for € 299,- potentially through eBay. I am also working on a "premium" version with SuperF Antennas for € 349,-
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xray
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Group: Forum Members
Posts: 2,
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+xGood news, now there is a ready-to-go Stratux FLARM image available which potentially will be updated on a regular basis:
Congratulations, TTS, right at the first time I visit this forum I find a brand-new solution for open source FLARM application by chance! Unfortunately I'm only an average SD user, and I would like to verify whether I got it right. The configuration You describe has tuned the 978 MHz (US weather etc.) for Europe to FLARM frequency. First question: Can other AC see me with this Stratux modification or can I only see their FLARM–signal on my unit? Is it ADS-B in and out? Second question: I read the whole SD thread, but I am new to github. Means: the link https://github.com/PepperJo/stratux/releases/tag/v1.4r5-flarm is cryptic to me. I think I have to start with a Stratux unit according to stratux.me and modify this in a second step. Could You please guide my mind towards this second step? For other prospective builders too a little tutorial would surely be helpful, and the idea would be worth spreading. I would appreciate it very much. Thanks Richard
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