Delineation of tree crown in high resolution satellite image using circle expression and watershed algorithm

Forests play an important role as environment for living things. For controlling forests, it is useful to know condition of tree efficiently. Recently, high spatial resolution images are taken using satellite and detail of trees in forest can be identified by visual inspection of satellite image. Shape of tree crown is one of important parameters that can be identified using satellite image. In this study, we developed a method to delineate crown and applied to high resolution satellite image. Then result of crown delineation was compared with result of visual inspection. At first, we assumed that shape of crown resembled circle and calculated circle radiuses showing crown size. Calculated radius was larger as similar brightness region became wide. The radiuses at each pixel position were calculated and the result was used as the radius distribution image (RDI). In the RDI, the radius was larger as the position became close to center part of crown. If radius value is considered as elevation, RDI seems to be DEM (Digital Elevation Model). The value of each pixel of RDI was inverted and inverse radius distribution image (IRDI) was calculated. In the IRDI, it is expected that a cone-shaped geographical feature is on the crown region and each crown region make each watershed. Then crown regions were calculated applying watershed algorithm to IRDI. In the results, shapes of calculated regions were close to crown shape identified with visual inspection