Method and apparatus for monitoring the integrity of satellite navigation signals

Apparatus for monitoring the integrity of satellite navigation signals, said apparatus comprising:

• first detection devices for a first detection of integrity problems, said first detection devices being configured to receive the same entity of a navigation signal from a specific satellite at different sites, and to evaluate the received entities to estimate both the error in the entity and the error introduced by the error estimation;
• second detection devices for a second detection of integrity problems, said second detection devices being configured to perform at least one measurement of at least one received navigation signal from a specific satellite, and to evaluate the at least one measurement to estimate both the error in the entity and the error introduced by the error estimation;
• and
• third detection devices for a third detection of integrity problems, said third detection devices being configured to perform measurements of several navigation signals from different satellites, and to jointly evaluate the measurements to determine the integrity risk;
• wherein
• the third detection devices are further configured so that integrity problems which are detectable during the first and second detections are taken into account only if they occur during the third detection, and have not been discovered during the first and second detection;
• the first and second detection devices detect different types of integrity problems;
• and
• integrity problems of the satellite navigation signals are detected using results of the first, second and third detections in combination.