Textural Characteristics Of Very High Spatial Resolution Optical Imagery Over Subtropical Plantation

Texture plays a very critical role in the application of high-resolution optical images.However,most of the existing studies have not paid enough attention to the optimization of texture variables and the optimal configuration of corresponding input parameters.Mingling is one of the important spatial structure indices to illustrate tree species segregation of mixed-species forest,which should be related to imagery textures.However,to the best of our knowledge,no specific research has been carried out on the relationship between mingling and image textures.In this paper,the Jiangle National Forest Farm in Fujian Province is taken as the research area.First,the Chinese fir plantations of different age groups at different slopes are taken as sample plots.Based on the Quick Bird image of the panchromatic band,the gray level co-occurrence matrix(GLCM)texture is calculated,and the separability J value is used.The texture variables and their corresponding parameter configuration ranges suitable for age group discrimination are selected,and the general change rule of each texture quantity with the input parameters is further clarified.Secondly,the GLCM texture variables of needle and broad-leaved mixed forest plots were extracted to obtain the texture features of high-resolution images of plantation with different mingling degrees,and finally the correlation between each texture feature value and the mingling degree was determined.The results of the study show that:(1)All textures except the GLCM mean are more discriminative for the three age groups on the shady slope than on the sunny slope,proving that the texture may restore part of the spectral information masked by the shadow.(2)The window size is the most critical input parameter of the texture of the statistical group and the ordered group.The appropriate window size is related to the resolution of the image and the spatial scale of the research object.For example,the sub-meter high-resolution optical image in this study is being planted.When dividing the age group,it is better to set the window to a larger window above 29.The contrast group texture is completely independent of the window size and can be set at will.(3)When applying statistics group and ordered group textures,there is no need to pay attention to the displacement,and when applying contrast group textures,you need to pay attention to the setting of the displacement.Applying statistical group textures,you need to pay attention to the calculation direction when the displacement is large;while applying contrast group and ordered group textures,you need to pay attention to the calculation direction when the displacement is small.(4)There is no obvious correlation between GLCM texture and traditional mingling degree.More explorations should be performed to explain the inconsistency between current results and the theoretical assumption.The conclusions of this paper can provide a practical reference for the optimal application of high-resolution optical image texture information,and the first attempt of exploring the application of imagery textures in mixed forests should be encouraged to performed further through.