Altitudes above 32786 m are not displayed in APRS.FI

Martin P Dr. Faust

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Jul 13, 2021, 8:13:32 AM7/13/21

to aprs.fi

Hello group,

we had a fantastic balloon flight yesterday as a school project in the Munich, Germany area with the callsign DN1JET. The balloon reached an altitude of over 38,000 m. We noticed that altitudes above 32,768 m are unfortunately not displayed in APRS.FI. That is a great pity. But we do not know the reason. Is it due to our probe (PicoAPRS-LiteV1), APRS.FI or other reasons? I would be very pleased to receive any feedback.

Regards, Martin

Shawn Stoddard

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Jul 13, 2021, 8:25:30 AM7/13/21

to 'Steffan Jeschek' via aprs.fi

That sounds like a data type issue. That just happens to be the largest value of an integer on most platforms.

Your next step would be to inspect packets to see where the value got clipped. It might be before apes.fi.

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Heikki Hannikainen

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Jul 13, 2021, 3:35:46 PM7/13/21

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The tracker was sending mic-e formatted packets, and at high altitudes the
altitude could not be decoded because it had invalid encoding. The badly
encoded altitude bytes ended up in the beginning of the comment field in
the decoding phase, as shown in the decoded packets here.

https://aprs.fi/?c=raw&call=DN1JET-11&limit=50&view=decoded

I'm suspecting the PicoAPRS did a miscalculation and encoded the altitude
wrong.

- Hessu

Kipton Moravec

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Jul 14, 2021, 2:21:29 AM7/14/21

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We flew a balloon to 132,000 feet, (which is 40233.6 Meters) and it was correct on APRS.FI.

I would suspect something before it got to the internet. What were you using for a GPS and a tracker?

We have had GPS units quit reporting between 30,000 and 38,000 feet (not meters). They would not report higher because they were optimized for cars. The UBlox out of the box will not go higher, but you can change it to Airplane mode with their configuration software and it will go to 50,000 meters or 164,000 feet.

I would suspect the tracker first. Because if you are getting to 32000 meters it is probably not the GPS.

Kip

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Stefan Pommerenk

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Jul 19, 2021, 1:36:23 AM7/19/21

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From just now:

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