Clock Ephemeris Covariance Matrix message

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Message type ID: 
28
Body: 

This is an optional message included in the last versions of the standards, but it is not considered in the baseline of EGNOS for the time being. Message type 28 may be broadcast to provide the relative covariance matrix for clock and ephemeris error. Each covariance matrix is updated on the same order as the long-term corrections. This is an expansion of the information contained in the 2UDRE in that it specifies the correction confidence as a function of user location. This way message type 28 provides increased availability inside the service area and increased integrity outside.

Each satellite covariance matrix is a function of satellite location, reference station observational geometry, and reference station measurement confidence. Consequently it is a slowly changing function of time and hence it is updated on the same order as the long-term corrections. Message type 28 definition is included in the section A.4.4.16 of MOPS.