Mapping of forest leaf area index (LAI) using airborne LiDAR data in an urban park, Shinjyuku Gyoen, Tokyo

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The urban heat island effect has become a concern. Toward measures against this phenomenon, it is important to quantify the heat energy exchanged between green areas and urbanized areas. LAI is used to estimate the quantity of heat energy exchanged between vegetation and the air, and it is onsite-measured directly by leaf sampling or indirectly by fish-eye image, which makes it difficult to perform in wide areas. Light detection and ranging (LiDAR), a laser-based remote sensing tool, is the most convenient way of measuring the horizontal and vertical distribution of leaf volume. The authors used LiDAR to map forest LAI in Shinjyuku Gyoen Park (0.8 km<SUP>2</SUP>), Tokyo, on a 5-m grid. Before mapping, the penetration efficiencies (percent of laser beams reflected by the ground) were determined from LiDAR data. From the calculated penetration efficiencies, a correlation equation (R<SUP>2</SUP>=0.75) was obtained between indirectly measured LAI (LAI=0.2-2.9 in forest) and the penetration efficiency for the park. Next, using the correlation equation, the penetration efficiency for the park was converted to LAI, and finally forest LAI was mapped. If forest LAI can be mapped for multiple areas in Tokyo, the currently available models can be used with greater accuracy for estimating the quantity of heat energy exchange of green areas.
社団法人日本写真測量学会の論文