PARAMETERS ACQUISITION FOR 3D TREE MODELING
USING THREE-LINE SENSOR
Methodology:
First of all, the whole procedure from data acquisition to model creation is shown in Figure 1.
Figure 1. Procedures from data acquisition to model creation
As you can see, the whole procedure mainly consists of three major parts and five phases; (a)
data acquisition, (b) parameter acquisition (b-1. trees trunk estimation, b-2. parameter
determination) and (c) modeler operation (c-1. primitive model creation, c-2. pruning).
In part 1., we've conducted an experiment using TLS and VLMS, and we've got scan data.
In part 2., we've converted acquainted data into image data, position data, etc., and then, we've
estimated and determined the parameters from the converted data to create 3D model using
modeler.
In part 3., we've created primitive 3D model from the parameters, firstly. And next, we've
pruned the model using commercial 3D modeler.
The details of each prodedures are as follows.
a. Data acquisition:
a-1. Sensor system
a-1-1. Three Line Sensor (TLS)
Three Line Sensor (TLS) are implemented in the sensor system. Each has an 8mm F4 fish-eye
lens with a vision field of 180 ° on it. In each snapshot, a single-row image (line image) of 1 × 2048
pixels, is captured on the scanning plane. Line images are captured at a rate of 80 Hz by each line camera.
Figure 2. Line images and an
example of a line-image strip
Figure 2 shows a strip of line image, where each column corresponds to the valid pixels of a line image.
a-1-2. Vehicle-borne Laser Mapping Scanner (VLMS)
Vehicle-borne Laser Mapping Scanner (VLMS) are used in the sensor system. In one scanning ( a range
scan line), the VLMS profiles 600 range points of the surroundings on the scanning plane within 300 ° .
A blind area of 60 ° exists, due to the hard ware configuration. The VLMS has a maximum range
distance of 100m and an average error of 3 cm. The frequency of the VLMS is 20Hz, implying that it
profiles 20 range scan lines per second. Figure 3 shows a piece of range image, where each column
corresponds to a range scan line, and range scan lines are aligned in the order of the measurement
sequence.
Figure 3. Laser range finder
and Example of range data
