def airspeed_estimate(GLOBAL_POSITION_INT, WIND):
    """estimate airspeed"""
    wind = WIND
    gpi = GLOBAL_POSITION_INT
    from pymavlink.rotmat import Vector3
    import math
    wind3d = Vector3(wind.speed * math.cos(math.radians(wind.direction)), 
        wind.speed * math.sin(math.radians(wind.direction)), 0)
    ground = Vector3(gpi.vx * 0.01, gpi.vy * 0.01, 0)
    airspeed = (ground + wind3d).length()
    return airspeed
