Package org.locationtech.jts.linearref
Class LengthIndexedLine
java.lang.Object
org.locationtech.jts.linearref.LengthIndexedLine
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 Summary
ConstructorsConstructorDescriptionLengthIndexedLine
(Geometry linearGeom) Constructs an object which allows a linearGeometry
to be linearly referenced using length as an index. -
Method Summary
Modifier and TypeMethodDescriptiondouble
clampIndex
(double index) Computes a valid index for this line by clamping the given index to the valid range of index valuesextractLine
(double startIndex, double endIndex) Computes theLineString
for the interval on the line between the given indices.extractPoint
(double index) Computes theCoordinate
for the point on the line at the given index.extractPoint
(double index, double offsetDistance) Computes theCoordinate
for the point on the line at the given index, offset by the given distance.double
Returns the index of the end of the linedouble
Returns the index of the start of the linedouble
indexOf
(Coordinate pt) Computes the minimum index for a point on the line.double
indexOfAfter
(Coordinate pt, double minIndex) Finds the index for a point on the line which is greater than the given index.double[]
Computes the indices for a subline of the line.boolean
isValidIndex
(double index) Tests whether an index is in the valid index range for the line.double
project
(Coordinate pt) Computes the index for the closest point on the line to the given point.
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Constructor Details
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LengthIndexedLine
Constructs an object which allows a linearGeometry
to be linearly referenced using length as an index.- Parameters:
linearGeom
- the linear geometry to reference along
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Method Details
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extractPoint
Computes theCoordinate
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
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extractPoint
Computes theCoordinate
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 pointoffsetDistance
- 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
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extractLine
Computes theLineString
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 intervalendIndex
- the index of the end of the interval- Returns:
- the linear interval between the indices
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indexOf
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. Useproject(org.locationtech.jts.geom.Coordinate)
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:
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indexOfAfter
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. Useproject(org.locationtech.jts.geom.Coordinate)
to compute a guaranteed result for points which may be far from the line.- Parameters:
pt
- a point on the lineminIndex
- the value the returned index must be greater than- Returns:
- the index of the point greater than the given minimum index
- See Also:
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indicesOf
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 occur in the same order).- Parameters:
subLine
- a subLine of the line- Returns:
- a pair of indices for the start and end of the subline.
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project
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
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getStartIndex
public double getStartIndex()Returns the index of the start of the line- Returns:
- the start index
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getEndIndex
public double getEndIndex()Returns the index of the end of the line- Returns:
- the end index
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isValidIndex
public boolean isValidIndex(double index) Tests whether an index is in the valid index range for the line.- Parameters:
index
- the index to test- Returns:
true
if the index is in the valid range
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clampIndex
public double clampIndex(double index) Computes a valid index for this line by clamping the given index to the valid range of index values- Returns:
- a valid index value
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