  The navigation systems of autonomous aircraft rely on the readings provided
by a suite of onboard sensors to estimate the aircraft state. In the case of
fixed wing vehicles, the sensor suite is composed by triads of accelerometers,
gyroscopes, and magnetometers, a Global Navigation Satellite System (GNSS)
receiver, and an air data system (Pitot tube, air vanes, thermometer, and
barometer), and is often complemented by one or more digital cameras. An
accurate representation of the behavior and error sources of each of these
sensors, together with the images generated by the cameras, in indispensable
for flight simulation and the evaluation of novel inertial or visual navigation
algorithms, and more so in the case of low SWaP (size, weight, and power)
aircraft, in which the quality and price of the sensors is limited. This
article presents realistic and customizable models for each of these sensors,
which have been implemented as an open-source C ++ simulation. Provided with
the true variation of the aircraft state with time, the simulation provides a
time stamped series of the errors generated by all sensors, as well as
realistic images of the Earth surface that resemble those taken from a real
camera flying along the indicated state positions and attitudes.
