15.5.417 pap

pap(ref, tgt)

[SOFA] Returns the position angle of p-vector tgt from p-vector ref. It is in the range from minus pi to plus pi radians. The vectors ref and tgt need not be of unit length. tgt and ref must have the same dimensions, and their first dimension must have 3 elements. The result has the same dimensions as tgt except that the first dimension (equal to 3) is omitted.