CurveToLineWithTolerance (geography Data Type)

Artikel
2024-11-22

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance SQL database in Microsoft Fabric

Returns a polygonal approximation of a geography instance that contains circular arc segments.

Syntax

  
.CurveToLineWithTolerance( tolerance, relative )

Arguments

tolerance
Is a double expression that defines the maximum error between the original circular arc segment and its linear approximation.

relative
Is a bool expression that indicates whether to use a relative maximum for the deviation. If relative is false (0), then an absolute maximum is set for the deviation that a linear approximate can have. When relative is true (1), then the tolerance is calculated as a product of the tolerance parameter and the bounding box's diameter for the spatial object.

Return Types

SQL Server return type: geography

CLR return type: SqlGeography

Exceptions

Setting tolerance <= 0 throws an ArgumentOutOfRange exception.

Remarks

This method allows for an error tolerance amount to be specified for the resultant LineString.

CurveToLineWithTolerance method will return a LineString instance for a CircularString or CompoundCurve instance and Polygon instance for a CurvePolygon instance.

Examples

A. Using different tolerance values on a CircularString instance

The following example shows how setting the tolerance affects the LineStringinstance returned from a CircularString instance:

DECLARE @g geography;  
SET @g = geography::Parse('CIRCULARSTRING(-122.358 47.653, -122.348 47.649, -122.348 47.658, -122.358 47.658, -122.358 47.653)');  
SELECT @g.CurveToLineWithTolerance(0.1,0).STNumPoints(), @g.CurveToLineWithTolerance(0.01, 0).STNumPoints();

B. Using the method on a MultiLineString instance containing one LineString

The following example shows what is returned from a MultiLineString instance that only contains one LineString instance:

DECLARE @g geography;  
SET @g = geography::Parse('MULTILINESTRING((-122.358 47.653, -122.348 47.649))');  
SELECT @g.CurveToLineWithTolerance(0.1,0).ToString();

C. Using the method on a MultiLineString instance containing multiple LineStrings

The following example shows what is returned from a MultiLineString instance that contains more than one LineString instance:

DECLARE @g geography;  
SET @g = geography::Parse('MULTILINESTRING((-122.358 47.653, -122.348 47.649),(-123.358 47.653, -123.348 47.649))');  
SELECT @g.CurveToLineWithTolerance(0.1,0).ToString();

D. Setting relative to true for an invoking CurvePolygon instance

The following example uses a CurvePolygon instance to call CurveToLineWithTolerance() with relative set to true:

DECLARE @g geography = 'CURVEPOLYGON(COMPOUNDCURVE(CIRCULARSTRING(-122.358 47.653, -122.348 47.649, -122.348 47.658), (-122.348 47.658, -122.358 47.658, -122.358 47.653)))';  
SELECT @g.CurveToLineWithTolerance(.5,1).ToString();

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