# Lesson 7: RECOGNITION OF ROAD BOUNDARIES, ROAD USERS AND OBSTACLES I: USING A CAMERA

In this lesson, we’ll delve into how autonomous vehicles utilize cameras to recognize road boundaries and identify obstacles, such as vehicles, cyclists, and pedestrians.

1. Introduction to Camera-Based Recognition
• Cameras play a pivotal role in the perception capabilities of autonomous vehicles.
• They are employed to identify crucial elements on the road, including road boundaries and various obstacles.
• This lesson provides fundamental insights into how camera imagery is processed to create a comprehensive view of the road environment.
1. Photogrammetry Basics
• Photogrammetry is the underlying technique used to convert camera images into a coherent representation of the road.
• While we won’t delve deeply into the technical intricacies, we will cover some fundamental photogrammetric concepts.
• Photogrammetry is a key component in the process of recognizing road boundaries and obstacles using cameras.
1. Camera Angle and Position
• Understanding the camera’s position and angle is essential for accurate recognition.
• Figure 1 illustrates the camera’s vertical angle (θ) and its inclination concerning the road’s horizontal plane.
• We assume constant road slope for simplicity but recognize that real-world scenarios may involve varying slopes.
• This foundational assumption aids in later calculations and can be refined to account for changing road slopes.

• The primary goal is to create a road layout display with moving and stationary obstacles based on camera input.
• Figure 2 exemplifies this by showing the desired output.
• Photogrammetric principles and equations will be employed to achieve this objective.

1. Camera Position in Vehicle Coordinate System
• Figure 3 depicts the camera’s position in relation to the vehicle’s coordinate system.
• Key points to note: point A on the road corresponds to point a in the camera image, and the distance between the lens and the observed objects is significant.
• This distance is equivalent to the focal length multiplied by the positive magnification.
•  Point a represents the position in the photograph of point A located on the road in front of the vehicle, with the following markings:

1. Camera Position in Vertical and Horizontal Plane
• Figure 4 shows the position of the camera in the vertical and horizontal plane, but also the position of points of interest.
• Figure 5 illustrates the camera’s position concerning the photograph’s dimensions (width W and height H).
• Point a on the photo corresponds to point A on the road.
• These insights help calculate key parameters such as azimuth, angle of depression, and distances between points.

1. Deriving Equations for Calculation
• Equations for various parameters will be derived to enable precise calculations, including:
• Azimuth of a point
• Angle of depression
• Coordinate x of point R
• Distances between points
• Distance between points A and B
• These calculations are instrumental in creating an accurate road layout.