Camera angle detection method and related surveillance apparatus

A surveillance apparatus, comprising:

• an image receiver adapted to acquire a surveillance image;
• and
• an operation processor electrically connected to the image receiver in a wire manner or in a wireless manner, the operation processor being adapted to detect a plurality of straight lines within the surveillance image, select at least one first candidate parallel line and at least one second candidate parallel line from the plurality of straight lines according to a directional trend, stretch the first candidate parallel line and the second candidate parallel line to acquire an intersection point, and compute parameter difference between the intersection point and a reference point of the surveillance image and transform the parameter difference for acquiring an inclined angle of an optical axis of a lens of the surveillance apparatus relative to a supporting plane whereon the surveillance apparatus is located.