Direction of Curvature

Maike · October 12, 2020, 9:04am

My calculations have shown that you do not differentiate between curvature to the right or left hand side when using
arcline_path_utils.get_curvature_at_distance_along_lane(distance_along_lane, lane_record)
from the tutorial to calculate the curvature at a specific point of the lane. Is that correct? For some cases this is kind of unhandy.

holger-motional · October 12, 2020, 10:48am

You are right. From the method docstring “Computes the unsigned curvature (1 / meters) at a distance along a lane.” Can’t you just post-process it and change the sign accordingly?

Maike · October 12, 2020, 11:33am

ok, you are right the method documentation even states it. What do you mean by post processing it? Currently, I can not think of an easy method to automatically determine afterwards if the lane goes to the right or the left.

holger-motional · October 13, 2020, 12:17am

Actually we have a method that does it for you:

github.com

nutonomy/nuscenes-devkit/blob/master/python-sdk/nuscenes/map_expansion/arcline_path_utils.py#L28


    :param angle_in_radians: Angle in radians.
    :return: Scaled angle in radians.
    """


    interval_min = -math.pi
    two_pi = 2 * math.pi
    scaled_angle = (angle_in_radians - interval_min) % two_pi + interval_min
    return scaled_angle




def compute_segment_sign(arcline_path: ArcLinePath) -> Tuple[int, int, int]:
    """
    Compute the sign of an arcline path based on its shape.
    :param arcline_path: arcline path record.
    :return: Tuple of signs for all three parts of the path. 0 if straight, -1 if right,
        1 if left.
    """
    shape = arcline_path['shape']
    segment_sign = [0, 0, 0]


    if shape in ("LRL", "LSL", "LSR"):

(I didn’t write the code so it took me some searching)