Measure Trunk Diameters
Measure Trunk Diameters tool supports the measurement of tree trunk diameters. It creates circular elements at the location of tree trunks detected in the point cloud. The elements represent the diameter of the trunk at the given height above the ground. Each created element stores the height from ground, and group identifier as an attribute. The measurements can be reported to a text file using Write group info -tool.
Trunk diameter measurement is most reliable done in very dense point clouds collected with a tripod-mounted scanner or a mobile scanner system. Then, the point cloud may be thinned during the processing workflow in order to reduce the amount of points.
The tool requires the computation of distance above ground values as well as group assignment (with Group by tree logic - Trunk method) for the point cloud data. The measurement may be further supported by the computation of normal vectors.
To measure trunk diameters:
1. Select Measure Trunk Diameters tool.
This opens the Measure Trunk Diameters dialog:
2. Define settings and click OK.
This creates circular elements at the location of the tree trunk measurement. The elements are placed on the active level using the active symbology of the CAD file. They may be modified using CAD tools.
SETTING |
EFFECT |
|---|---|
Groups with |
Determines which groups are considered: •One or more points - groups with one or more points in the source class. •Majority of points - groups with the majority of points in the source class. •All points - groups with all points in the source class. |
Class |
Point class(es) that include the tree trunks. |
|
Opens the Select classes dialog which contains the list of active classes in TerraScan. You can select multiple source classes from the list that are then used in the Class field. |
Inside fence |
Determines how a fence or selected polygon(s) effect the trunk measurement: •Not used - fence or selected polygons are ignored. •One or more points - groups are classified if one or more points are inside. •Average xy - groups are classified if the average xy point is inside. •Majority of points - groups are classified if the majority of points is inside. •All points - groups are classified if all points are inside. |
Use pulse vector |
If on, TerraScan uses the laser beam direction to identify open space and solid objects. Enabling the option can reduce false findings. |
Measure |
Whether to measure One diameter at breast height or Multiple diameters along the complete tree trunk to measure the trunk volume. |
At height |
Height from ground at which the trunk diameter is measured. This is available only if Measure is set to One diameter. |
First height |
Height from ground at which the trunk diameter measurements begin. This is available only if Measure is set to Multiple diameters. |
Interval |
Trunk measurement interval. This is available only if Measure is set to Multiple diameters. |
Last height |
Height from ground at which the trunk diameter measurements end, even if point data would be available higher. Use to limit unreliable measurements high from ground based scanner. |
Diameter |
Tolerance for filtering gross errors in the trunk diameter measurements. The tree height is defined by the point highest from ground in the group. |
Tolerance |
Determines the expected measurement spread and allowed difference of a trunk section from a circular shape. |
Filter points by neighbourhood |
If on, the spread around the dominant trunk surface is filtered. This option requires the normal vectors. |
