EW Avionics IGC File Format - Character Mappings

Ed Davies
EW Avionics
1998-December-21

Introduction

When EWView exports a trace in the IGC format certain fields from the EWT file are copied directly to the output file. Unfortunately, the character set allowed in these fields in the IGC format is a subset of the set of characters which are possible in the EWT file.

Some fields in the EWT file are stored using a large subset of the standard IBM character set (code page 850 - Multilingual (Latin 1)). This subset includes the whole of the printable ASCII character set.

Fields in the IGC file format are a restricted to a subset of the printable ASCII characters. This is therefore a subset of the characters possible in the EWT file.

Characters in the relevant EWT fields which are not contained in IGC subset are mapped to characters which are in order to ensure that a valid IGC file is produced.

The field which is most affected by this mapping is the EWT comment text which is included in the IGC file as a (possibly empty) sequence of logbook records. This can contain any of the printable characters allowed in an EWT file.

Other fields which potentially could be affected include the glider, pilot and GPS receiver fields ("pilot info" fields in the EW FR Model D) and turn point names in a declaration and datum names from the GPS receiver. Currently EWView/DOS checks the contents of the declaration fields prior to download (applying the mapping documented here as the characters are typed in by the user) and all characters which appear in datum names produced by approved GPS receivers fall within the IGC character set so mapping of these fields is not currently essential.

In future, a more robust version of EWView/DOS might check these fields while preparing for export and warn if the there are unsupported characters present. This would only be useful if there was any software in existence which allowed the download of characters outside the IGC subset. Applying any mapping to these fields prior to export is of questionable value as it would prevent VALI-EWA calculating the correct checksum. Before deciding whether to perform such a mapping it would be necessary to weigh up the consequences of causing the security code to not match making the file insecure for IGC purposes against the consequences for analysis software of reading files which do not comply strictly with the standard.

In the absence of such non-conforming declaration download software the addition of this check is not urgent.

(The comment text is not included in the checksum so these considerations does not apply to it).

Mappings

The general principle followed is that EWT characters which are in the allowed IGC character set are preserved, the remainder are either mapped to sensible alternatives or to '#' (hash/pound/number sign/sharp).

Note - the character names used in the following table are purly for descriptive purposes. They are not in anyway definitive names.

EWT Char			IGC Char
Hex	Char	Name	Hex	Char	Name
00-19		Control Chars	23	#	Hash
20		Space	20		Space
21	!	Exclamation mark	23	#	Hash
22	"	Double Quote	22	"	Double Quote
23	#	Hash	23	#	Hash
24	$	Dollar	23	#	Hash
25	%	Percent	25	%	Percent
26	&	Ampersand	26	&	Ampersand
27	'	Single Quote	27	'	Single Quote
28	(	Open Parenthesis	28	(	Open Parenthesis
29	)	Close Parenthesis	29	)	Close Parenthesis
2A	*	Asterisk	23	#	Hash
2B	+	Plus	2B	+	Plus
2C	,	Comma	3B	;	Semicolon
2D	-	Minus	2D	-	Minus
2E	.	Point	2E	.	Point
2F	/	Slash	2F	/	Slash
30-39	0..9	Digits	30-39	0..9	Digits
3A	:	Colon	3A	:	Colon
3B	;	Semicolon	3B	;	Semicolon
3C	<	Less Than	3C	<	Less Than
3D	=	Equal	3D	=	Equal
3E	>	Greater Than	3E	>	Greater Than
3F	?	Question Mark	3F	?	Question Mark
40	@	At	40	@	At
41-5A	A..Z	Upper Case Letters	41-5A	A..Z	Upper Case Letters
5B	[	Open Bracket	5B	[	Open Bracket
5C	\	Backslash	23	#	Hash
5D	]	Close Bracket	5D	]	Close Bracket
5E	^	Circumflex	23	#	Hash
5F	_	Underscore	5F	_	Underscore
60	`	Open Single Quote	60	`	Open Single Quote
61..7A	a..z	Lower Case Letters	61..7A	a..z	Lower Case Letters
7B	{	Open Braces	7B	{	Open Braces
7C	|	Vertical Bar	7C	|	Vertical Bar
7D	}	Close Braces	7D	}	Close Braces
7E	~	Tilde	23	#	Hash
7F		Del	23	#	Hash
80	Ç	Upper Case C Cedilla	43	C	Upper Case C
81	ü	Lower Case U Umlaut	75	u	Lower Case U
82	é	Lower Case E Acute	65	e	Lower Case E
83	â	Lower Case A Circumflex	61	a	Lower Case A
84	ä	Lower Case A Umlaut	61	a	Lower Case A
85	à	Lower Case A Grave	61	a	Lower Case A
86	å	Lower Case A Ring	61	a	Lower Case A
87	ç	Lower Case C Cedilla	63	c	Lower Case C
88	ê	Lower Case E Circumflex	65	e	Lower Case E
89	ë	Lower Case E Umlaut	65	e	Lower Case E
8A	è	Lower Case E Grave	65	e	Lower Case E
8B	ï	Lower Case I Umlaut	69	i	Lower Case I
8C	î	Lower Case I Circumflex	69	i	Lower Case I
8D	ì	Lower Case I Grave	69	i	Lower Case I
8E	Ä	Upper Case A Umlaut	41	A	Upper Case A
8F	Å	Upper Case A Ring	41	A	Upper Case A
90	É	Upper Case E Acute	45	E	Upper Case E
91	æ	Lower Case AE Dipthong	23	#	Hash
92	Æ	Upper Case AE Dipthong	23	#	Hash
93	ô	Lower Case O Circumflex	6F	o	Lower Case O
94	ö	Lower Case O Umlaut	6F	o	Lower Case O
95	ó	Lower Case O Grave	6F	o	Lower Case O
96	û	Lower Case U Circumflex	75	u	Lower Case U
97	ù	Lower Case U Grave	75	u	Lower Case U
98	ÿ	Lower Case Y Umlaut	79	y	Lower Case Y
99	Ö	Upper Case O Umlaut	4F	O	Upper Case O
9A	Ü	Upper Case U Umlaut	55	U	Upper Case U
9B	ø	Lower Case O Slash	23	#	Hash
9C	£	Pound	23	#	Hash
9D	Ø	Upper Case O Slash	23	#	Hash
9E	×	Multiply	23	#	Hash
9F	ƒ	Eff Thingy	23	#	Hash
A0	á	Lower Case A Acute	61	a	Lower Case A
A1	í	Lower Case I Acute	69	i	Lower Case I
A2	ó	Lower Case O Acute	6F	o	Lower Case O
A3	ú	Lower Case U Acute	75	u	Lower Case U
A4	ñ	Lower Case N Tilde	6E	n	Lower Case N
A5	Ñ	Upper Case N Tilde	4E	N	Upper Case N
A6		Superscript Lower Case A Underscore	23	#	Hash
A7		Superscript Lower Case O Underscore	23	#	Hash
A8	¿	Inverted Question Mark	23	#	Hash
A9	®	Registered Symbol	23	#	Hash
AA	¬	Not/Bar	23	#	Hash
AB	½	Half	23	#	Hash
AC	¼	Quarter	23	#	Hash
AD	¡	Inverted Exclamation	23	#	Hash
AE	«	Open Angle Quotes	23	#	Hash
AF	»	Close Angle Quotes	23	#	Hash
B0-B4		Line Drawing Characters	23	#	Hash
B5	Á	Upper Case A Acute	41	A	Upper Case A
B6	Â	Upper Case A Circumflex	41	A	Upper Case A
B7	À	Upper Case A Grave	41	A	Upper Case A
B8	©	Copyright	23	#	Hash
B9-BC		Line Drawing Characters	23	#	Hash
BD	¢	Cent	63	c	Lower Case C
BE	¥	Yen	23	#	Hash
BF-C5		Line Drawing Characters	23	#	Hash
C6	ã	Lower Case A Tilde	61	a	Lower Case A
C7	Ã	Upper Case A Tilde	41	A	Upper Case A
C8-CE		Line Drawing Characters	23	#	Hash
CF	¤	Currency Symbol	23	#	Hash
D0		Lower Case Delta	64	d	Lower Case D
D1	Ð	Upper Case D Bar	44	D	Upper Case D
D2	Ê	Upper Case E Circumflex	45	E	Upper Case E
D3	Ë	Upper Case E Umlaut	45	E	Upper Case E
D4	È	Upper Case E Grave	45	E	Upper Case E
D5		Line Drawing Character	23	#	Hash
D6	Ì	Upper Case I Grave	49	I	Upper Case I
D7	Î	Upper Case I Circumflex	49	I	Upper Case I
D8	Ï	Upper Case I Umlaut	49	I	Upper Case I
D9-DD		Line Drawing Characters	23	#	Hash
DE	Ì	Upper Case I Grave	49	I	Upper Case I
DF		Line Drawing Character	23	#	Hash
E0	Ó	Upper Case O Acute	4F	O	Upper Case O
E1	ß	Double S	53	S	Upper Case S
E2	Ô	Upper Case O Circumflex	4F	O	Upper Case O
E3	Ò	Upper Case O Grave	4F	O	Upper Case O
E4	õ	Lower Case O Tilde	6F	o	Lower Case O
E5	Õ	Upper Case O Tilde	4F	O	Upper Case O
E6	µ	Micro	23	#	Hash
E7	Þ	Lower Case Eth/Thorn?	23	#	Hash
E8	þ	Upper Case Eth/Thorn?	23	#	Hash
E9	Ú	Upper Case U Acute	55	U	Upper Case U
EA	Û	Upper Case U Tilde	55	U	Upper Case U
EB	Ù	Upper Case U Grave	55	U	Upper Case U
EC	ý	Lower Case Y Acute	79	y	Lower Case Y
ED	Ý	Upper Case Y Acute	59	Y	Upper Case Y
EE		Overbar	23	#	Hash
EF		Acute	23	#	Hash
F0		Bar	23	#	Hash
F1	±	Plus or Minus	23	#	Hash
F2		Equal	23	#	Hash
F3	¾	Three Quarters	23	#	Hash
F4	¶	Paragraph	23	#	Hash
F5	§	Section	23	#	Hash
F6	÷	Divide	23	#	Hash
F7		Tadpole	23	#	Hash
F8	°	Degree	64	d	Lower Case D
F9		Minute	23	#	Hash
FA		Second	23	#	Hash
FB	¹	Superscript 1	23	#	Hash
FC	²	Superscript 2	23	#	Hash
FD	³	Superscript 3	23	#	Hash
FE		Block	23	#	Hash
FF			23	#	Hash