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Defined in: iLand\tree_doc.js:1
Module: iLand

A Tree object allows accessing individual trees (>4m height) in iLand via Javascript.

Note that using Javascript with individual trees can be slow.

Accessing a tree

Trees can be accessed via the Management object or TreeList list within ABE. The Management object provides tree and treeObject functions. Similarly, the TreeList includes tree and treeObject.

Reference vs object

iLand provides two distinct ways to access trees, namely as reference (to an internal object) or as a Javascript object. Access via reference is faster, but tree references can not be used for later access. See the example:

// load all trees of resource unit 0:
management.loadResourceUnit(0);
// access via reference: every call to the tree() functions modifies the reference:
var t1=management.tree(0); // the first tree (dbh=10)
var t2=management.tree(1); // the second tree (dbh=20)
console.log("Tree1: " + t1.dbh + ", Tree2: " + t2.dbh); // -> yields "Tree1: 20, Tree2: 20"!!!!

// access via object:
var t1=management.treeObject(0); // the first tree (dbh=10)
var t2=management.treeObject(1); // the second tree (dbh=20)
console.log("Tree1: " + t1.dbh + ", Tree2: " + t2.dbh); // -> yields "Tree1: 10, Tree2: 20"

// References are, however, useful for iterating over a list of trees:
var sum_dbh=0;
for (var i=0;i<management.count;++i)
    sum_dbh += management.tree(i).dbh;
console.log("Mean dbh: " + sum_dbh / management.count);

Item Index

Methods

Properties

Methods

expr

(
  • expression
)
Double

expr() can be used to retrieve the value of an iLand expression iland.boku.ac.at/Expression. All tree variables can be accessed via the expression. Note that the expression is a string and can contain mathematical operations and a set of pre-defined functions.

See also: TreeExpr

Parameters:

  • expression String

    iLand tree expression

Returns:

Double:

value of the expression for the tree.

Example:

var tree = trees.tree(0); // trees is a TreeList
                    console.log( tree.expr("dbh*dbh") ); // print the squared dbh

info

() String

A string with memory address, Id, dbh, height, and coordinates of the tree.

Returns:

String:

A human-readable string with key characteristics of the tree.

Properties

dbh

Double

The dbh (diamter at breast height), in cm.

species

String

The species (4-character species ID), e.g. 'piab'.

valid

Bool

false if the tree object is not valid, true otherwise.

x

Double

The x-coordinate of the tree, in m.

y

Double

The y-coordinate of the tree, in m.