The development of the Galileo program is currently dealing with the definition of the local elements in order to complete the overall system architecture. The design of original systems, different and improved with respect to the traditional local segments of GPS may enrich Galileo of additional features providing added value to the system. In this paper, we propose a novel local area augmentation system based on the use of stratospheric High Altitude Platforms (HAPs), unmanned aircraft performing long endurance operation at an altitude of about 20 km. Several aeronautical projects developed in different research laboratories around the world demonstrate that the design of a "near eternal airplane" is a feasible task, and that such aircrafts will be delivered in a near future at affordable costs [1][2]. For these reasons HAPs are candidate to host payload for the provision of communications services over large regions, playing the role of very small satellites almost stationary and near to the ground with respect to low Earth orbit spacecrafts. This paper discusses the use of HAPs for the provision of augmentation signals for Galileo (aerial transponder for local differential corrections), and introduces the concept of stratolite (stratospheric-pseudo-satellite), as an aerial pseudo satellite able to provide differential corrections modulated over a satellite-like signal. The main topics of the system concept definition are discussed in order to demonstrate the feasibility of a payload providing navigation services and the expected advantage
