研究目的
To compare hemispherical photography and aerial photography measurement as the input data of canopy density estimation using Sentinel-2 imagery.
研究成果
Downward method produces higher canopy density data than upward method. When it was correlated and analyzed using simple linear regression, both methods provide good correlation and accuracy using vegetation index, and several band ratios. However the term of downward measurement is more appropriate to canopy density term. Upward method provides the good method in canopy density estimation based on remote sensing data in this study area.
研究不足
The visual interpretation in downward measurement can lead to errors in the results. The classification on downward measurement could also be conducted by the per-pixel classification method, but it was not performed in this research. The use of hemisphere lens can be the source of error in upward measurement.
1：Experimental Design and Method Selection:
The study compares two methods of canopy density measurement: aerial photography via drone (downward measurement) and hemispherical photography (upward measurement).
2：Sample Selection and Data Sources:
The study area is located in Universitas Gadjah Mada (UGM) campus, with two sites: campus forest at Faculty of Forestry and Wisdom Park.
3：List of Experimental Equipment and Materials:
DJI Phantom-4 drone for aerial photography and a fish-eye camera for hemispherical photography. Sentinel-2 imagery was used as the remote sensing data.
4：Experimental Procedures and Operational Workflow:
Aerial photography was acquired by making flight paths and flying the drone following its paths while taking photos. Hemispherical photography was applied by taking photos vertically upward using a fish-eye camera.
5：Data Analysis Methods:
The canopy density was obtained by differentiating the canopy object from sky object using Can-Eye software for hemispherical photography. For aerial photography, land cover interpretation was conducted on each grid by distinguishing canopy, shrub, herb, water body, pavement, and bare soil.
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