def get_azpl(cdec, cinc, gdec, ginc):
    """
     gets azimuth and pl from specimen dec inc (cdec,cinc) and gdec,ginc (geographic)  coordinates
    """
    TOL = 1e-4
    rad = old_div(np.pi, 180.)
    Xp = dir2cart([gdec, ginc, 1.])
    X = dir2cart([cdec, cinc, 1.])
    # find plunge first
    az, pl, zdif, ang = 0., -90., 1., 360.
    while zdif > TOL and pl < 180.:
        znew = X[0] * np.sin(pl * rad) + X[2] * np.cos(pl * rad)
        zdif = abs(Xp[2] - znew)
        pl += .01

    while ang > 0.1 and az < 360.:
        d, i = dogeo(cdec, cinc, az, pl)
        ang = angle([gdec, ginc], [d, i])
        az += .01
    return az - .01, pl - .01
gets azimuth and pl from specimen dec inc (cdec,cinc) and gdec,ginc (geographic)  coordinates