Public Member Functions

geos::linearref::LengthIndexedLine Class Reference

Supports linear referencing along a linear Geometry using the length along the line as the index. Negative length values are taken as measured in the reverse direction from the end of the geometry. Out-of-range index values are handled by clamping them to the valid range of values. Non-simple lines (i.e. which loop back to cross or touch themselves) are supported. More...

#include <LengthIndexedLine.h>

List of all members.

Public Member Functions

 LengthIndexedLine (const geom::Geometry *linearGeom)
 Constructs an object which allows a linear Geometry to be linearly referenced using length as an index.
geom::Coordinate extractPoint (double index) const
 Computes the Coordinate for the point on the line at the given index. If the index is out of range the first or last point on the line will be returned. The Z-ordinate of the computed point will be interpolated from the Z-ordinates of the line segment containing it, if they exist.
geom::Coordinate extractPoint (double index, double offsetDistance) const
 Computes the Coordinate for the point on the line at the given index, offset by the given distance.
geom::GeometryextractLine (double startIndex, double endIndex) const
double indexOf (const geom::Coordinate &pt) const
double indexOfAfter (const geom::Coordinate &pt, double minIndex) const
double * indicesOf (const geom::Geometry *subLine) const
double project (const geom::Coordinate &pt) const
double getStartIndex () const
double getEndIndex () const
bool isValidIndex (double index) const
double clampIndex (double index) const

Detailed Description

Supports linear referencing along a linear Geometry using the length along the line as the index. Negative length values are taken as measured in the reverse direction from the end of the geometry. Out-of-range index values are handled by clamping them to the valid range of values. Non-simple lines (i.e. which loop back to cross or touch themselves) are supported.


Constructor & Destructor Documentation

geos::linearref::LengthIndexedLine::LengthIndexedLine ( const geom::Geometry linearGeom  ) 

Constructs an object which allows a linear Geometry to be linearly referenced using length as an index.

Parameters:
linearGeom the linear geometry to reference along

Member Function Documentation

double geos::linearref::LengthIndexedLine::clampIndex ( double  index  )  const

Computes a valid index for this line by clamping the given index to the valid range of index values

Returns:
a valid index value
geom::Geometry* geos::linearref::LengthIndexedLine::extractLine ( double  startIndex,
double  endIndex 
) const

Computes the LineString for the interval on the line between the given indices. If the endIndex lies before the startIndex, the computed geometry is reversed.

Parameters:
startIndex the index of the start of the interval
endIndex the index of the end of the interval
Returns:
the linear interval between the indices
geom::Coordinate geos::linearref::LengthIndexedLine::extractPoint ( double  index,
double  offsetDistance 
) const

Computes the Coordinate for the point on the line at the given index, offset by the given distance.

If the index is out of range the first or last point on the line will be returned. The computed point is offset to the left of the line if the offset distance is positive, to the right if negative.

The Z-ordinate of the computed point will be interpolated from the Z-ordinates of the line segment containing it, if they exist.

Parameters:
index the index of the desired point
offsetDistance the distance the point is offset from the segment (positive is to the left, negative is to the right)
Returns:
the Coordinate at the given index
geom::Coordinate geos::linearref::LengthIndexedLine::extractPoint ( double  index  )  const

Computes the Coordinate for the point on the line at the given index. If the index is out of range the first or last point on the line will be returned. The Z-ordinate of the computed point will be interpolated from the Z-ordinates of the line segment containing it, if they exist.

Parameters:
index the index of the desired point
Returns:
the Coordinate at the given index
double geos::linearref::LengthIndexedLine::getEndIndex (  )  const

Returns the index of the end of the line

Returns:
the end index
double geos::linearref::LengthIndexedLine::getStartIndex (  )  const

Returns the index of the start of the line

Returns:
the start index
double geos::linearref::LengthIndexedLine::indexOf ( const geom::Coordinate pt  )  const

Computes the minimum index for a point on the line. If the line is not simple (i.e. loops back on itself) a single point may have more than one possible index. In this case, the smallest index is returned.

The supplied point does not necessarily have to lie precisely on the line, but if it is far from the line the accuracy and performance of this function is not guaranteed. Use project to compute a guaranteed result for points which may be far from the line.

Parameters:
pt a point on the line
Returns:
the minimum index of the point
See also:
project
double geos::linearref::LengthIndexedLine::indexOfAfter ( const geom::Coordinate pt,
double  minIndex 
) const

Finds the index for a point on the line which is greater than the given index. If no such index exists, returns minIndex. This method can be used to determine all indexes for a point which occurs more than once on a non-simple line. It can also be used to disambiguate cases where the given point lies slightly off the line and is equidistant from two different points on the line.

The supplied point does not necessarily have to lie precisely on the line, but if it is far from the line the accuracy and performance of this function is not guaranteed. Use project to compute a guaranteed result for points which may be far from the line.

Parameters:
pt a point on the line
minIndex the value the returned index must be greater than
Returns:
the index of the point greater than the given minimum index
See also:
project
double* geos::linearref::LengthIndexedLine::indicesOf ( const geom::Geometry subLine  )  const

Computes the indices for a subline of the line. (The subline must conform to the line; that is, all vertices in the subline (except possibly the first and last) must be vertices of the line and occcur in the same order).

Parameters:
subLine a subLine of the line
Returns:
a pair of indices for the start and end of the subline.
bool geos::linearref::LengthIndexedLine::isValidIndex ( double  index  )  const

Tests whether an index is in the valid index range for the line.

Parameters:
length the index to test
Returns:
true if the index is in the valid range
double geos::linearref::LengthIndexedLine::project ( const geom::Coordinate pt  )  const

Computes the index for the closest point on the line to the given point. If more than one point has the closest distance the first one along the line is returned. (The point does not necessarily have to lie precisely on the line.)

Parameters:
pt a point on the line
Returns:
the index of the point

The documentation for this class was generated from the following file: