The present invention relates to providing navigation guidance for mobile users, using Global Navigation Satellite Systems (GNSSs) for applications where the user position needs to be determined in real time while meeting the navigation requirements, especially integrity requirement, for the given application. The present invention assists in providing guidance with a high availability of integrity function by trading accuracy for integrity for two different types of navigation applications. A first type of application requires a capability of detecting an occurrence of multiple satellite signal faults; the first embodiment of the invention provides this capability with a high availability of integrity, using two or more independent GNSSs. A second type of application requires a capability of detecting an occurrence of a single satellite signal fault; the second embodiment of the invention provides this capability with a high availability of integrity, using any one or a combination of GNSSs. The detecting and deriving of both methods are (i) in position domain and (ii) determinative of mobile user safety.