The designers of the JCMT software require azimuth, yaw, roll, and pitch
as the columns of the file MODEL1.dat, where the three motions are
known as F1, F2 & F3. This file is referenced by the TEL task
by toggling the parameter point_model to 1 inside
radio_telescope.dat. These files may be found in the directory known
as jcmtdata_dir.
F1, F2 & F3 are described in MTUN025 thus :
F1 - Change in the azimuth encoder value.
F2 - Variation of 
. . the telescope model parameter
describing the non-orthogonality
of the elevation axis w.r.t. the azimuth axis.
F3 - Change in elevation encoder value.
As Section 5 of MTUN025, "SIGNS", says, "There is ample scope
for confusion", and I refer the concerned reader to that document if the
following is not clear.
F1 is +ve when the antenna experiences a clockwise yaw. This occurs when
the top of the RHAF tilts backwards, and / or
the top of the LHAF tilts forwards. These occur when
the RHAF front leg rises and /or
the RHAF rear leg drops and /or
the LHAF front leg drops and /or
the LHAF front leg rises. (RHAF = Right Hand A-Frame, etc)
F2 is +ve when the elevation axis tilts down to the right or up to the left.
F3 is +ve when the antenna tips upwards.