**3. Methodology**

#### **3.1 Camera system**

Catenary components to be checked are mounted in a large area. It covers [−3500, 3500 mm] in the horizontal direction and [4800, 8100 mm] in the vertical direction relative to the track center. High-resolution image data are needed in order to perform image detection of each component.

In our system, the candidate detection area is divided into several detection regions. A dedicated designed camera system is mounted on an inspection car, which is composed of many area-scan cameras with different directions and fields of view. Super-high-resolution cameras are used which have a resolution up to 29 megapixel.

**Table 1** gives details of the camera system. The camera system is carefully designed so that it covers almost all the components to be checked with an image resolution up to 0.5 mm/pixel, which gives great details of each component.

In order to get a brighter light and better image quality at night, groups of strobe light are applied in the system.

**Figure 6** illustrates the design for part of the camera system.
