Using robots and UAVs(unmanned aerial vehicles) for surveying transmission lines and towers is standard practice. Applications such as painting and NDT (non-destructive testing) require the UAV to be in close proximity to the surface of the structure. Typically, UAV systems consist of GPS(global positioning system), cameras, and high computing devices mounted to perform SLAM to locate and navigate. Most vision-based SLAM (simultaneous localization and mapping) algorithms use spatial features to localize and map. Structures such as transmission towers are highly symmetric, which may make the SLAM system difficult to localize. Even with accurate localization, it is hard to calculate the trajectory which covers the surface area with proximity, which is another problem to solve to automate the process. The paper proposes a CAD (computer-aided design) model-based navigation method for UAVs around transmission towers that can be deployed in low-power devices. The CAD model provides crucial information, which can be just enough to plan the path/motion around the transmission tower. The algorithm pipeline starts with finding the flat surfaces of the CAD model and sampling them. Using those sampled points, estimate the possible site around the tower where the drone could fly. After that, sampled points are filtered to find the possible trajectory to cover the surface.