def draw_arc(self, color, world_loc, world_radius, start_angle, stop_angle,
               thickness=1):
    """Draw an arc using world coordinates, radius, start and stop angles."""
    center = self.world_to_surf.fwd_pt(world_loc).round()
    radius = max(1, int(self.world_to_surf.fwd_dist(world_radius)))
    rect = pygame.Rect(center - radius, (radius * 2, radius * 2))
    pygame.draw.arc(self.surf, color, rect, start_angle, stop_angle,
                    thickness if thickness < radius else 0)