The objective of this project is to demonstrate that crowd-sensed GNSS signals can be effectively used as the sole (or main) data source for an integrity service. Integrity will be provided by allowing the user to assess his guaranteed positioning performance. This is achieved by providing statistical bounds to the residual error components (after applying potential corrections and removing signals impacted by feared events) and transferring these to the position domain in the user receiver. The feasibility and benefits of MAGIE will be assessed by large-scale simulations, possibly assisted by actual measurements. The simulations in the project will follow a multi-layered approach (3 steps) to reduce the simulation load, to allow to assess the effectiveness of the protection against feared events in an efficient manner.