ZOO.Geometry.LinearRing

A Linear Ring is a special LineString which is closed. It closes itself automatically on every addPoint/removePoint by adding a copy of the first point as the last point.

Also, as it is the first in the line family to close itself, a getArea() function is defined to calculate the enclosed area of the linearRing

Inherits from

• ZOO.Geometry.LineString

Properties

NAME	DESCRIPTION
componentTypes	{Array(String)} An array of class names representing the types of components that the collection can include.

Functions

NAME	DESCRIPTION
ZOO.Geometry.LinearRing	Linear rings are constructed with an array of points.
addComponent	Adds a point to geometry components.
move	Moves a geometry by the given displacement along positive x and y axes.
rotate	Rotate a geometry around some origin
resize	Resize a geometry relative to some origin.
transform	Reproject the components geometry from source to dest.
getCentroid	{ZOO.Geometry.Point} The centroid of the ring
getArea
getGeodesicArea	Calculate the approximate area of the polygon were it projected onto the earth.
containsPoint	Test if a point is inside a linear ring.

Properties

componentTypes

{Array(String)} An array of class names representing the types of components that the collection can include. A null value means the component types are not restricted.

Functions

ZOO.Geometry.LinearRing

Linear rings are constructed with an array of points. This array can represent a closed or open ring. If the ring is open (the last point does not equal the first point), the constructor will close the ring. If the ring is already closed (the last point does equal the first point), it will be left closed.

Parameters

points {Array(ZOO.Geometry.Point)} points

addComponent

addComponent: function(point,index)

Adds a point to geometry components. If the point is to be added to the end of the components array and it is the same as the last point already in that array, the duplicate point is not added. This has the effect of closing the ring if it is not already closed, and doing the right thing if it is already closed. This behavior can be overridden by calling the method with a non-null index as the second argument.

Parameter

point {ZOO.Geometry.Point}

index {Integer} Index into the array to insert the component

Returns

{Boolean} Was the Point successfully added?

move

move: function(x,y)

Moves a geometry by the given displacement along positive x and y axes. This modifies the position of the geometry and clears the cached bounds.

Parameters

x {Float} Distance to move geometry in positive x direction.

y {Float} Distance to move geometry in positive y direction.

rotate

rotate: function(angle,origin)

Rotate a geometry around some origin

Parameters

angle {Float} Rotation angle in degrees (measured counterclockwise from the positive x-axis)

origin {ZOO.Geometry.Point} Center point for the rotation

resize

resize: function(scale,origin,ratio)

Resize a geometry relative to some origin. Use this method to apply a uniform scaling to a geometry.

Parameters

scale {Float} Factor by which to scale the geometry. A scale of 2 doubles the size of the geometry in each dimension (lines, for example, will be twice as long, and polygons will have four times the area).

origin {ZOO.Geometry.Point} Point of origin for resizing

ratio {Float} Optional x:y ratio for resizing. Default ratio is 1.

Returns

{ZOO.Geometry} The current geometry.

transform

transform: function(source,dest)

Reproject the components geometry from source to dest.

Parameters

source {ZOO.Projection}

dest {ZOO.Projection}

Returns

{ZOO.Geometry}

getCentroid

getCentroid: function()

Returns

{ZOO.Geometry.Point} The centroid of the ring

getArea

getArea: function()

Note

The area is positive if the ring is oriented CW, otherwise it will be negative.

Returns

{Float} The signed area for a ring.

getGeodesicArea

getGeodesicArea: function(projection)

Calculate the approximate area of the polygon were it projected onto the earth. Note that this area will be positive if ring is oriented clockwise, otherwise it will be negative.

Parameters

projection {ZOO.Projection} The spatial reference system for the geometry coordinates. If not provided, Geographic/WGS84 is assumed.

Reference

Robert. G. Chamberlain and William H. Duquette, “Some Algorithms for Polygons on a Sphere”, JPL Publication 07-03, Jet Propulsion Laboratory, Pasadena, CA, June 2007 http://trs-new.jpl.nasa.gov/dspace/handle/2014/40409

Returns

{float} The approximate signed geodesic area of the polygon in square meters.

containsPoint

containsPoint: function(point)

Test if a point is inside a linear ring. For the case where a point is coincident with a linear ring edge, returns 1. Otherwise, returns boolean.

Parameters

point {ZOO.Geometry.Point}

Returns

{Boolean | Number} The point is inside the linear ring. Returns 1 if the point is coincident with an edge. Returns boolean otherwise.