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室内高光谱遥感定量反演土壤湿度的相关研究,可以为利用星载或机载遥感数据源进行大尺度土壤水分监测提供理论基础;原状土土样相较于当前广泛使用的研磨土土样,能更好地保持土壤的原始光谱特性和持水性能。为了得到更可靠的土壤湿度光谱特征与更具有适用性的反演模型,利用ASD Field Spec 3光谱仪采集了江苏省金坛市竹林镇的62个原状水稻土土样12套不同湿度梯度的可见光-近红外反射光谱,通过反射率、相对反射率以及水分吸收峰特征参数探究原状湿土光谱特征;在此基础上,选择对土壤湿度变化响应明显的变量,采用偏最小二乘回归反演土壤湿度,并对比选出最佳反演模型。结果表明:(1)随着风干过程中土壤湿度的降低:土壤反射率整体先下降后上升,可见光波段在土壤湿度较低时存在误差;1450 nm和1950 nm吸收峰的位置向短波方向偏移,吸收峰深度、宽度和面积不断减小,2 200 nm处吸收峰右肩高度不断降低。(2)土壤水分吸收峰特征参数对土壤湿度响应明显;反射率和相对反射率与土壤湿度相关性较高的波段均出现在>1300 nm以后。(3)反射率(R)反演原状土湿度精度较低,R2val=0.752,RPD=1.81,经过数学形式和相对反射率(Rr)变换后,[lg(1/Rr)]’建模中R2val=0.820,RPD=1.99;基于水分吸收峰特征参数建立的模型R2val=0.800,RMSEP=62.70 g kg-1,RPD=2.29,最佳主成分数为3,是反演原状土土壤湿度的最佳建模变量。
Indoor hyperspectral remote sensing quantitative retrieval of soil moisture related research, can provide a theoretical basis for large-scale soil moisture monitoring using satellite or airborne remote sensing data source; undisturbed soil samples compared with the widely used soil samples, Can better maintain the original spectral characteristics of the soil and water holding capacity. In order to obtain more reliable spectral characteristics of soil moisture and more suitable inversion models, 12 samples of 62 undisturbed paddy soil samples collected from Zhulin Town, Jintan City, Jiangsu Province, were collected using ASD Field Spec 3 spectrometer. Near-infrared reflectance spectroscopy was used to explore the spectral characteristics of undisturbed wet soils based on the reflectance, relative reflectance and moisture absorption peak parameters. Based on this, the variables that responded well to the changes of soil moisture were selected and the partial least-squares regression was used to retrieve the soil moisture , And compared the best inversion model selected. The results showed as follows: (1) With the decrease of soil moisture during air drying, the soil reflectance firstly decreased and then increased, and the error of visible light band was low when the soil moisture was low. The positions of 1450 nm and 1950 nm absorption peaks were shifted toward shortwave , The absorption peak depth, width and area continue to decrease, the absorption peak at 2 200 nm continuously reduces the height of the right shoulder. (2) The characteristic parameters of soil moisture absorption peak have obvious response to soil moisture; the band with higher correlation between reflectance and relative reflectance and soil moisture appears after> 1300 nm. (3) Reflectivity (R) Inversion of original soil moisture accuracy is low, R2val = 0.752, RPD = 1.81, After the mathematical form and relative reflectivity (Rr) transformation, [lg R2val = 0.820, RPD = 1.99; R2val = 0.800, RMSEP = 62.70g kg-1, RPD = 2.29, and the optimal principal component is 3. Based on the characteristic parameters of moisture absorption peak, Good modeling variables.