No, "first" infers a sequence and is associated with the beginning of that sequence. In the case of a relative heading, the existing heading is 0 degrees. Any

No, "first" infers a sequence and is associated with the beginning of that sequence. In the case of a relative heading, the existing heading is 0 degrees. Any change is relative to that origin point. Zero is also not the absence of anything, that would more properly be considered a NULL or NaN.