IGC Filename Decoding


Maybe you have wondered about the file names of the IGC log files that are generated by your flight recorder. For example, "15KC3WK1.IGC". It looks like a strange random combination of letters and numbers, but each character does have a meaning. In the example above it means, "1st Flight on May 20th, 2011* using a Cambridge flight recorder serial number 3WK". Simple? Not so much.

Here is what each digit means in the IGC filename;
Format: YMDCXXXF.IGC

  • Y=Last digit of year
  • M=Month of year (1-9, A-C)**
  • D=Day of month (1-9, A-V)**
  • C=Manufacturer of logger
  • XXX=Serial number of logger (3 alpha-numeric digits)
  • F=Flight number of day (1-9, A-Z)**
  • IGC=File extension name

To ease the decoding of the convoluted IGC file name, I created a "simple" spreadsheet to decode these file names and as a teaching aid so that after a while you can figure the dates yourself just by looking at them. You might find this useful if you are sorting through a bunch of old log files.


WARNING: I suggest that you do not rename your IGC files. There have been reports of renamed IGC files causing scoring problems at contests and for badges. If you want to keep a renamed file, only rename a copy of the original, and keep the original "pristine".


*NOTE: Due to limitations of the IGC file naming standard (DOS 8.3) and the IGC standard only one character is available to represent the year**). Therefore, flights during years ending in the same digit will be listed in the spreadsheet as occurring in the closest year within the current decade.

For example, the years 1994, 2004 and 2014 all have the same trailing digit ("4"). Therefore, flights during those years will all have the same first "Y" digit in the IGC filename ("4"). Because the spreadsheet cannot tell the difference, all flights will indicate a flight year of 2014.

The actual date and time of the flight is shown within the text of the IGC log file (so you can't cheat!). Sorry folks, but there is no way around this in my spreadsheet without reading the contents of the file, which Excel cannot directly do (if you know how, let me know).

See the table below for date examples to help illustrate this issue;


Current Year = 2016

The GREEN highlighted boxes shown below indicates that
the CORRECT year is calculated by the spreadsheet.

Flight
Year
(Actual)
Flight Year
Shown in
Spreadsheet
First Digit
of IGC
Filename
2016 2016 6
2015 2015 5
2014 2014 4
2013 2013 3
2012 2012 2
2011 2011 1
2010 2010 0
2009 2009 9
2008 2008 8
2007 2007 7


The ORANGE highlighted boxes shown below indicates that
the WRONG year is calculated by the spreadsheet and
is off by a one or more decades due to the first digit
of the IGC filename being the same as in the above table.

Flight
Year
(Actual)
Flight Year
Shown in
Spreadsheet
First Digit
of IGC
Filename
Error
(Years)
2006 2016 6 +10
2005 2015 5 +10
2004 2014 4 +10
2003 2013 3 +10
2002 2012 2 +10
2001 2011 1 +10
2000 2010 0 +10
1999 2009 9 +10
1998 2008 8 +10
1997 2007 7 +10
1996 2016 6 +20
1995 2015 5 +20


Please see this spreadsheet for IGC file decoding and more details.

Other information can be found at the International Air Sports Federation (FAI) Gliding (IGC) web site.


Free tools to view IGC files:


** Due to the limitations of the old DOS 8.3 file naming convention, the IGC filename uses only one character to represent the day, month and flight number. Values below 10 are easy and are represented by the logical characters 1 to 9. However, values of 10 to 35 are now represented by the characters A to Z.

For example, if the day of the month is the "5th", this is represented by a "5". Easy. But the "11th" is above 9 so it is now represented by the letter "B". Say the month is December (12th month). This is now represented by the letter "C". More than 9 flights in a day? Got you covered but only up to 35 flights ("Z"). Let me know if you had 35 flights in one day - that has to be a record of some sort!

The alignment of the single IGC filename characters to their true meanings are shown in the table below and in the spreadsheet.

Character
in IGC
Filename
Numerical
Value
Day of
Month
Month
Flight
No.
1 1 1st January 1
2 2 2nd February 2
3 3 3rd March 3
4 4 4th April 4
5 5 5th May 5
6 6 6th June 6
7 7 7th July 7
8 8 8th August 8
9 9 9th September 9
A 10 10th October 10
B 11 11th November 11
C 12 12th December 12
D 13 13th 13
E 14 14th 14
F 15 15th 15
G 16 16th 16
H 17 17th 17
I 18 18th 18
J 19 19th 19
K 20 20th 20
L 21 21st 21
M 22 22nd 22
N 23 23rd 23
O 24 24th 24
P 25 25th 25
Q 26 26th 26
R 27 27th 27
S 28 28th 28
T 29 29th 29
U 30 30th 30
V 31 31st 31
W 32 32
X 33 33
Y 34 34
Z 35 You've
gotta' be
kidding

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