GDL90 GPS Altitude msl vs WGS-84 ellipsoid #749
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Add setting's switch for ownship geometric altitude message in GDL90 to enable altitude in MSL instead of altitude above WGS-84 ellipsoid. GDL90 specification uses WGS-84 ellipsoid altitude but some EFBs expect altitude in MSL. https://www.faa.gov/nextgen/programs/adsb/Archival/media/GDL90_Public_ICD_RevA.PDF Signed-off-by: PepperJo <pepperjo@japf.ch>
GPL90 traffic reports expect barometric altitude. Convert GNSS altitudes in traffic information to barometric altitude. Estimate barometric altitude from reported GPS geoid height, own geoid separation and barometric pressure. Signed-off-by: PepperJo <pepperjo@japf.ch>
Add GPS height above WGS-84 ellispoid to the website. Signed-off-by: PepperJo <pepperjo@japf.ch>
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@PepperJo - all of the EFBs on our compatibility list expect the altitude to be MSL. It was implemented wrong by most ADS-B portables, so we deviated from the spec on this since MSL was the "de-facto" standard. What EFBs expect it to be WGS-84, and is it possible to auto-detect them so that we can avoid adding extra options? |
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From this forum posts: http://forums.skydemon.aero/Topic19950-11.aspx |
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Stratux tracks client states. We used to shut off AHRS output only for detected ForeFlight clients because of a bug in ForeFlight. Something similar can be done to output WGS-84 if SkyDemon can be detected. |
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I will take a look and update the pull request accordingly if I find a decent solution. |
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See |
@cyoung - your EFB compatibility list is missing some very popular European EFBs which I already tested successfully with Stratux: SkyDemon (only Traffic):
Sky-Map (Traffic & AHRS):
Air Nav Pro (only Traffic):
EasyVFR (Traffic & AHRS):
Airmate (only Traffic):
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I will split this pull request since it tackles 3 different problems... |
This pull request introduces a switch to the settings page to switch between GPS altitude MSL or height above WGS-84 ellipsoid for the GDL90 ownship geometric altitude message. GDL90 specifies ownship geometric altitude as height above WGS-84 ellipsoid but some EFBs expect MSL altitude. We leave the default to MSL but allow switching to height above ellipsoid.