STAsBinary (geography Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
SQL database in Microsoft Fabric
Returns the Open Geospatial Consortium (OGC) Well-Known Binary (WKB) representation of a geography instance.
This geography data type method supports FullGlobe instances or spatial instances that are larger than a hemisphere.
Syntax
.STAsBinary ( )
Return Types
SQL Server return type: varbinary(max)
CLR return type: SqlBytes
Remarks
The OGC type of a geography instance can be determined by invoking STGeometryType().
Examples
The following example uses STAsBinary() to create a LineString``geography instance from (-122.360, 47.656) to (-122.343, 47.656) from text. It then returns the result in WKB.
DECLARE @g geography;
SET @g = geography::STGeomFromText('LINESTRING( -122.360 47.656, -122.343 47.656)', 4326);
SELECT @g.STAsBinary();