In the ARINC specification, why is baro altitude (label 204) measured in Knots? I am currently designing a system that reads the baro altitude (on label 204) from an LRU. Ultimately in my software I would like to display the baro altitude reading in real-time using a graphical interface. In doing this, I'd like to have the units of measurement next to the reading. However I am having a bit of trouble in deciding how to display the units of measurement.

In the ARINC specification (attachment 2 "data standards"), label 204 (baro altitude) is listed as having units of knots. Is this an error, or can altitude be in Knots?

I am referencing ARINC specification 429 part 1-17, mark 33 digital information transfer system (DITS) published in May of 2004.
It's an error. Attachment 2B does show that label 204 from the GNLU (Equip ID 056) and GLU (Equip ID 060) as being in knots (highlighted below). That is not correct, it is a BNR in feet as shown for Air Data System (ID 006) and ADIRU (ID 038). Knots only applies to Label 204 from the FMS (ID 002).  



It's still incorrect in A429 P1-18, March 2012.  

ARINC 429 contact at ARINC Industry Activities, ARINC 429 Maintenance is Jose Godoy. email:jose.godoy@sae-itc.org