return turning circle (diameter) in meters for steering_angle in degrees

def rover_turn_circle(SERVO_OUTPUT_RAW):
    '''return turning circle (diameter) in meters for steering_angle in degrees
    '''

    # this matches Toms slash
    max_wheel_turn = 35
    wheelbase      = 0.335
    wheeltrack     = 0.296

    steering_angle = max_wheel_turn * (SERVO_OUTPUT_RAW.servo1_raw - 1500) / 400.0
    theta = radians(steering_angle)
    return (wheeltrack/2) + (wheelbase/sin(theta))