pap¶
- erfa.pap(a, b)[source]¶
Position-angle from two p-vectors.
- Parameters:
- adouble array
- bdouble array
- Returns:
- c_retvaldouble array
Notes
Wraps ERFA function
eraPap
. The ERFA documentation is:- - - - - - - e r a P a p - - - - - - - Position-angle from two p-vectors. Given: a double[3] direction of reference point b double[3] direction of point whose PA is required Returned (function value): double position angle of b with respect to a (radians) Notes: 1) The result is the position angle, in radians, of direction b with respect to direction a. It is in the range -pi to +pi. The sense is such that if b is a small distance "north" of a the position angle is approximately zero, and if b is a small distance "east" of a the position angle is approximately +pi/2. 2) The vectors a and b need not be of unit length. 3) Zero is returned if the two directions are the same or if either vector is null. 4) If vector a is at a pole, the result is ill-defined. Called: eraPn decompose p-vector into modulus and direction eraPm modulus of p-vector eraPxp vector product of two p-vectors eraPmp p-vector minus p-vector eraPdp scalar product of two p-vectors This revision: 2021 May 11 Copyright (C) 2013-2023, NumFOCUS Foundation. Derived, with permission, from the SOFA library. See notes at end of file.