IGC file format

[Piet Barber]

Hello, 

I've been snooping around a recent IGC file recorded on my LX9070 with a text editor. (Since I'm a unix administrator by day, this is normal behavior, looking at text files trying to reverse engineer them)

I found these entries: 

LLXVFF193435TR AR A9D661 39.16742N78.14655W -30000 2200 55.5 4.2 21 0 0
LLXVFF193456TR AR A9D661 39.16687N78.13312W 2425 2500 55.5 -1.3 21 0 1
LLXVFF193517TR AR A9D661 39.16216N78.12006W 2375 2400 57.6 0.3 21 0 1
LLXVFF193539TR AR A9D661 39.15518N78.10870W -30000 2300 60.7 -1.6 21 0 0

Neat!  That Hex code is definitely an N number.  Using this ICAO converter: http://www.avionictools.com/icao.php, I can convert it to an N number.  I can look up that guy's ADS-B information on FlightAware for that day and see his flight.  Cool!  So the PowerFLARM is sending information about nearby aircraft (and by nearby, this guy was maybe 30 km away or so)

What are all the other data columns?  Those are LLX Fields, so I don't think I can find their information in the official IGC file format definition. L records are Logbook records, and it seems the IGC doesn't have a fixed format for what follows the first "L".  My best guess would be:

LLXVFF(HHMMSS)TR AR (Aircraft ICAO hex ID) (lat)N(long)W (altitude) (altitude) (velocity (m/s)) (climb/sink?) (?) (?) (?)

My original mission was to see if there is a log of the outside air temperature in the IGC file. 

LLXVFF16220039 PWR STATE 4 LVL 23 BAT 0.00 EXT 11.87 TEMP 15.7

Is this in fact the temperature?  Is it recorded in Farenheit and not Celcius? 15.7F seems right, 15.7C seems wrong.  Since I'm in the US, I'm forced to use non-metric units. 

--

Piet Barber
http://www.pietbarber.com/
http://blog.pietbarber.com/

[cdeerinck]

Piet,

Funny, I just posted this yesterday.  The details for the IGC file can be found here:

    https://www.fai.org/sites/default/files/igc_fr_specification_2020-11-25_with_al6.pdf

The offset for the OAT (Outside Air Temp) can be found in the I record (it only occurs near the beginning of the file), and for my LX9070 it is bytes 60 thru 62.  Per the spec (bottom of Page 38), it is given in degrees C.  (Hint: it is way colder outside that inside at altitude)

Lots of cool info in the IGC files.

~Chuck

[Piet Barber]

 Sorry! I get this mailing list in digest format and didn't see it until now.  Thanks for the info.