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Color infrared aerial images to evaluate tree crown defoliation
Date Issued |
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2009 |
The relationship between the radiometric and textural characteristics of color infrared aerial images and the tree crown defoliation at a single tree level is studied on a test area in Aukstaitija integrated monitoring station. The spatial resolution of images was 15 cm; around 2500 trees were measured in the field, geo-referenced and detected on the images. Relatively strongest correlation between tree crown defoliation and mean pixel valuesof color-infrared images was observed just for near infrared image band (correlation coefficient -0,47 for pine trees, which prevailed in the study area). Green and red image bands resulted in low and statistically insignificant correlations. Correlation coefficient increased if just dominating pine trees were taken into account. Coefficient of correlation between mean pixel values of near infrared band and the defoliation of dominating pine trees was -0.63. Standart deviation of pixel values correlated with ihe defoliation of sheltered trees best no matter the image band (correlation coefficients fluctuated around -0.45).