Electronics and Vision System of a Projectile-Drone Hybrid System ing system (GPS). For the information of height, however, a Kalman filter merging the data from the barometer, GPS, and range finder (if available) was implemented. In this way, the bias of the barometer is suppressed by using the absolute reference of the GPS, while keeping the good dynamic range of the barometer signal. Inertial sensors are also used to establish a criterion of motion. If it is detected that the drone does not move (when it is in the gun), the evolution of the bias of the barometer can be estimated. Figure 8 presents the results obtained on real data coming from a GLMAV launching. The launch occurs at time t = 487.2 seconds, and an important spike resulting from the high pressure is visible on the barometer measurements. It quickly recovers. GPS altitude is available after less than 3 seconds of ballistics, which corresponds to a hot start (a three-dimensional [3D] fix is obtained before the GLMAV is put in Figure 4. Schematic diagram of the interprocessor communication. Figure 5. Real-time task organization. 42 IEEE A&E SYSTEMS MAGAZINE OCTOBER 2017