EnvelopeAggregate (geography Data Type)
Returns a bounding object for a given set of geography objects. The resulting geography object contains multiple circular arc segments.
Applies to: SQL Server (SQL Server 2012 through current version), Azure SQL Database.
A FullGlobe object is returned when the resulting bounding object is bigger than a hemisphere. This method is not precise.
Method returns null if the input has different SRIDs. See Spatial Reference Identifiers (SRIDs).
Method ignores null inputs.
Method returns null if all inputted values are null.