coords.py 文件源码

def calc_user_look_at(pos_sat, lat, lon, alt, t):
    pos = calc_pos(lat, lon, alt, t)
    rx = pos_sat.x - pos.x
    ry = pos_sat.y - pos.y
    rz = pos_sat.z - pos.z
    jd = julian_date(t)
    theta = (theta_g_JD(jd) + lon) % TWO_PI

    top_s = sin(lat) * cos(theta) * rx +  \
        sin(lat) * sin(theta) * ry -  \
        cos(lat) * rz
    top_e = -sin(theta) * rx + \
        cos(theta) * ry
    top_z = cos(lat) * cos(theta) * rx +  \
        cos(lat) * sin(theta) * ry +  \
        sin(lat) * rz

    az = atan(-top_e/top_s)
    if top_s > 0:
        az += pi
    if az < 0:
        az += TWO_PI

    rg = (rx*rx + ry*ry + rz*rz)**0.5
    el = asin(top_z/rg)
    return (az, el, rg)