AsTextZM (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 Text (WKT) representation of a geography instance augmented with any Z (elevation) and M (measure) values carried by the instance.
Syntax
.AsTextZM ()
Return Types
SQL Server return type: nvarchar(max)
CLR return type: SqlChars
Remarks
Examples
The following example creates a Point instance that contains Z (elevation) and M (measure) values. STAsText() selects the WKT values, (-122.34900 47.65100); AsTextZM() selects the same WKT values and also returns the values for Z and M, yielding (-122.34900 47.65100 10.3 12).
DECLARE @g geography;
SET @g = geography::STGeomFromText('POINT(-122.34900 47.65100 10.3 12)', 4326);
SELECT @g.STAsText();
SELECT @g.AsTextZM();