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. Outofrange index values are handled by clamping them to the valid range of values. Nonsimple lines (i.e. which loop back to cross or touch themselves) are supported.
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#include <LengthIndexedLine.h>
List of all members.
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. Outofrange index values are handled by clamping them to the valid range of values. Nonsimple 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 Zordinate of the computed point will be interpolated from the Zordinates 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 Zordinate of the computed point will be interpolated from the Zordinates 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:

 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 nonsimple 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:

 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:

 Returns:
 the index of the point
The documentation for this class was generated from the following file: