Estimation of Biomass using Three-Dimensional Scanning System
4. Estimation of Biomass
In biomass measurement(Fig.6), these data can be obtained.
- Reflectance data by multi spectrometer.
- Digital images by digital camera.
- Dried weight of plants by cutting grasses.
- Grass height
By using these data, biomass parameters can be obtained. Vegetation coverage ratio (VC
R) is estimated from reflectance data and digital images. The biomass data, such as drie
d weight can be expressed in terms of the relation between the VCR and grass height
Biomass = f(VCR, h) (1)
where h is the grass height, Biomass is the dried weight of plants. Also, these 2 data is
obtained by three dimensional scanning system.
Three dimensional structural data of plants.
Reflectance of laser at the wavelength of 680nm.
Grass height h is measured from three dimensional data. Wavelength of 680nm is an ab
sorption band of vegetation. So we can detect the plants by the reflectance data. As ass
ume that the three dimensional data consists of a lot of voxels, the volume of vegetatio
n and the vegetation coverage ratio (VCR) can be obtained. Because of these data, it is
possible to estimate the biomass data from the three dimensional structural data of plant
s.
5. Data Analysis
5.1 Preprocessing
Before the data analysis, It is need to preprocessing, such as enhancement, and pick up
the plants from three-dimensional structural data. Before and after the enhancement imag
e is shown at Fig. 8 and Fig.9.
5.2 Estimation of Vegetation Coverage Ratio(VCR)
After the preprocessing, we estimated the vegetation coverage ratio (VCR) of quadrat.
VCR can be estimated by counting the points of plants(Fig. 10).
5.3 Estimation of Grass Height
From three-dimensional structural data, grass height data can be obtained. The compar
ed graph of grass height data is shown in Fig.11. This grass height data was obtained b
y man and three-dimensional data.
5.3 Estimation of Biomass
In biomass measurement, we cut grasses of four quadrat of three-dimensional scanning
measurement area and measured the dried weight of these grasses. And also we estimate
d the biomass using the three-dimensional structural data. The compared result of these t
wo measurement is shown in Table.1.
Table 1. Estimated Biomass
| Quadrat |
Dried Weight(g) |
Esstimated Biomass |
| CA03 |
38.26 |
179.94 |
| CA06 |
34.78 |
156.38 |
| CA09 |
42.21 |
246.80 |
| CA0f |
50.92 |
373.39 |
In these result of analysis, we can see some relations between three-dimensional st
ructural data and data obtained by biomass measurement.
But there is many difference between these data. One reason of this difference is m
iss extraction of grass part from three-dimensional structural data.
