Unmanned aerial vehicles are being increasingly used in challenging applications, such as environmental monitoring and surveying, precision agriculture, and mitigation actions in disaster sites. Visual cameras constitute an important component of a UAV sensor suite, allowing the vehicle to perceive the surrounding environment, and perform tasks such as mapping, 3D reconstruction, and path planning. In this work, a simulator reproducing the output of a visual camera transported onboard a UAV is proposed. The objective of the simulator is to assist the user in defining the most suitable camera configuration before going through field development and testing. Special focus is given to the realistic rendering of the environment. In this paper, first, the main elements of the simulator, including environment modeling, vehicle trajectory and camera modeling are described. Then, the use of the simulator to analyze the influence of some main camera parameters on the output ofthe imaging process is shown. Finally, the application of the simulator for the generation of aerial mosaics using Google Earth data is presented.