STNumPoints (geography Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Returns the total number of points in each of the figures in a geography instance.
Syntax
.STNumPoints ( )
Return Types
SQL Server return type: int
CLR return type: SqlInt32
Remarks
This method counts the points in the description of a geography instance. Duplicate points are counted; however, connecting points between segments are counted only once. If this instance is a collection, this method returns the total number of points in the collection.
Examples
A. Retrieving the total number of points in a LineString
The following example creates a LineString instance and uses STNumPoints() to determine how many points were used in the description of the instance.
DECLARE @g geography;
SET @g = geography::STGeomFromText('LINESTRING(-122.360 47.656, -122.343 47.656)', 4326);
SELECT @g.STNumPoints();
B. Retrieving the total number of points in a GeometryCollection
The following example returns a sum of the points for all elements in the GeometryCollection.
DECLARE @g geography = 'GEOMETRYCOLLECTION(CIRCULARSTRING(-122.358 47.653, -122.348 47.649, -122.348 47.658, -122.358 47.658, -122.358 47.653)
,CURVEPOLYGON(CIRCULARSTRING(-122.358 47.653, -122.348 47.649, -122.348 47.658, -122.358 47.658, -122.358 47.653)))';
SELECT @g.STNumPoints();
C. Returning the number of points in a CompoundCurve
The following example returns the number of points in a CompoundCurve instance. The query returns 5 instead of 6 because STNumPoints() only counts the connecting point between the segments once.
DECLARE @g geography = 'COMPOUNDCURVE(CIRCULARSTRING(-122.358 47.653, -122.348 47.649, -122.348 47.658),( -122.348 47.658, -121.56 48.12, -122.358 47.653))'
SELECT @g.STNumPoints();