Design and implementation of a mini quadrotor control system in GPS denied environments This paper presents the design of quadrotor control architecture, based on crowd-sourcing electronics. The aim of this quadrotor is to provide a test-bed for vision-based autonomous navigation system inGPS denied environments. The control architecture consists of a cascaded structure, where an attitude controller nested in velocity and altitude controllers. The sub-controllers are all linear controllers with feedforward term to linearize the quadrotor dynamics. The control and sensor fusion algorithm is developed under Arduino compatible open source electronics, whereas the complete design also includes an additional downward facing optical flow sensor (PX4FLOW camera) for horizontal velocity estimation and vehicle altitude estimation, and a separate Linux embedded computer (Odriod-U3) for future Simultaneous Localization And Mapping (SLAM) vision algorithm development. In current stage, by utilizing the PX4FLOW sensor, it is capable of horizontal velocity control and altitude hold. Besides, a ground station GUI software is developed in MATLAB® for two-way telemetry visualization and in-air parameter tuning.