Bar-Coded Boarding Passes (BCBP) Implementation guide - IATA

Appendix
Figure 96 - PDF417 is composed of 4 elements whose widths add up to 17 modules
X
Parameter Definition Recommendation
Width of a module. The X Dimension
should be constant throughout a
symbol
A minimum X dimension is
recommended in the IATA standard
(see Appendix C)
Y Row height. The PDF417 standard recommends
that Y ≥ 3X.
Algorithms then relate codewords and ASCII characters. Data compaction schemes are used to
achieve high level encoding. The text compaction mode encodes up to 2 characters per
codeword. It includes all printable ASCII characters plus three control characters: tab, line feed
and carriage return. In byte compaction mode, the algorithm converts six data bytes to five
PDF417 data codewords. In numeric compaction mode, the algorithm converts 44 consecutive
numeric digits to 15 or fewer PDF417 data codewords. Numeric compaction is used to encode
long strings of consecutive numeric digits.
Although PDF417 is a 2D bar code, it is in reality a stack of 1D bar codes. The decode algorithm
uses scan lines which enables laser scanners that read 1D bar codes to also read PDF417 (see
fig. 90), whereas the laser scanners would not read 2D matrix codes.
Figure 97 - Schematic showing a scan line crossing rows of the PDF417 symbol
4 th edition - June 2009 - www.iata.org/stb/bcbp 107/128