# A Study on Highway Driving Assist Evaluation Method Using the Theoretical Formula and Dual Cameras
## 2 Theoretical Background
### Selecting the Optimal Installation Location for Dual Camera  
In previous studies [16], for vehicle testing, a theoretical formula for measuring the distance to an object in front using a dual camera was proposed. Moreover, a study was conducted to select the optimal location of the dual camera.  
Variables for selecting the optimal position of the dual camera are height, spacing, and angle. The reason why the camera installation height is selected as a variable is that the lower the height the wider the area of the ground captured in the video. The reason why the camera installation interval is selected as a variable is that it affects distance measurement according to the installation interval of two cameras. The reason why the camera's photographing angle is selected as a variable is that a camera having a small vertical angle of view cannot photograph a short-range ground. Table 1 is the result of summarizing the test results for selecting the optimal mounting position of the dual camera. The average error rate and the maximum error rate, according to the combination of each variable, are shown.  
The value of the variable considers the specifications of the camera and vehicle. The variables of the camera height are 30 cm, 40 cm, and 50 cm. The reason why the minimum value is selected as 30 cm is that the bumper height of a typical sedan is higher than 30 cm, so the camera cannot be physically mounted at a position lower than 30 cm. The reason for selecting the maximum value of 50 cm is that if the mounting height is greater than 50 cm, the ground within 1 m cannot be photographed due to the vertical angle of view of the camera used in the test. The variables of the camera baseline are 10 cm, 20 cm, and 30 cm. The reason why the minimum value is selected as 10 cm is that the distance between the left and right camera lenses cannot be smaller than 10 cm because of the size of the camera used in the test. In addition, 20 cm and 30 cm were additionally set to confirm the tendency for the value of the mounting interval. The variables of the camera angle are 3\({}^{\circ}\), 7\({}^{\circ}\), and 12\({}^{\circ}\). This considers the position of the preceding vehicle and the ground captured in the image. For example, the reason why the minimum value is set to 3\({}^{\circ}\) is that the ground within 1 m cannot be photographed when the value is less than 3\({}^{\circ}\) due to the mounting height and the vertical angle of view of the camera. In addition, the reason why the maximum value is set to 12\({}^{\circ}\) is that when the mounting angle is greater than 12\({}^{\circ}\), the area occupied by the ground in the image increases, and the horizon is located at the top of the image, making it difficult to photograph a preceding vehicle located at a distance of 10 m or more.  
As an experiment of each variable, when the camera installation height was 40 cm, the camera installation interval was 30 cm, and the camera shooting angle was 12 degrees, the best results were derived, so this was selected as the optimal location. The reason why the camera installation height was selected as 40 cm was that when the height increased from 30 cm to 40 cm, the error rate decreased, and when the height increased from 40 cm to 50 cm, the error rate increased. The reason why the camera installation interval was selected as 30 cm was that the error rate tended to decrease as the interval increased. The reason why the camera photographing was selected at an angle of 12 degrees was that the error rate was likely to decrease while the value increased.