高光譜影像之地形輻射改正

Topographic Correction for Hyperspectral Imagery

張瑋(Chang Wei)

指導教授 ： 徐百輝

國立臺灣大學/工學院/土木工程學研究所/碩士(2015年)

https://doi.org/10.6342/NTU.2015.01024

摘要

高光譜影像提供豐富且細緻的地物光譜反射資訊，並已廣泛地應用於地物判釋及分析當中。高光譜影像所記錄的光譜反射資料主要來自於太陽輻射，經過大氣及地表交互作用後被感測器所記錄，因此光譜輻射資料均須進行大氣改正與地形改正。過去無論是空載或星載高光譜影像因空間解析度較低，大都僅進行大氣改正，但隨著低空光譜成像儀的發展，現今已經可以獲取具有高空間解析度的高光譜影像，也因此地形效應所造成的光譜反射曲線差異也更趨明顯，故如何改正地形效應對於光譜反射曲線的影響成為目前的研究議題之一。在分析地形與反射光譜交互作用的相關研究中，大都以雙向反射分布函數(bidirection reflectance distribution function, BRDF)為主要的數學模型。由於影響BRDF的因素眾多，除了太陽入射角、感測器的觀測角度、及地形的變化之外，最主要的輸入資訊－地形資料也是重要的影響要素。本研究欲建立一適用於高光譜之地形改正的BRDF模型，以數值地形模型(Digital Elevation Model , DEM)、數值地表模型(Digital Surface Model , DSM)和點雲三種地形資訊紀錄資料的型態做為本模型的測試及探討。結果顯示為高解析度的點雲資料在各個測試區域的成果最佳。

關鍵字

BRDF ； 高光譜影像 ； 地形資料

並列摘要

In most of the applications, the spectral radiance stored in the hyperspectral image has to be calibrated into the spectral reflectance previously through the radiance correction. We have already had many models to deal with radiance correction, however, most of them assume that the surface is horizontal and has a Lambertian reflectance. The reason may be that the real hyperspectral data typical do not have the enough surface information for topographic correction. Nowadays, there are various way to acquire the spatial information about the earth surface precisely, which provides an opportunity to enrich the descriptions of topography in correction models. Among the researches about interaction between topography and reflectance spectrum, the bidirectional reflectance distribution function (BRDF) is the most general mathematic model. The propose of this research aim at using the topographic data, likes digital elevation model (DEM), digital surface model (DSM) and point cloud data, to promote the description of topography in the correction model and offer exploratory discussion of topographic correction of the hyperspectral images. According to this, this study will correct the topography effect of the real high resolution hyperspectral images, using DEM, DSM and point cloud as topographic data, testing the correction model built in this research.

並列關鍵字

BRDF ； hyperspectral imagery ； topographic information

參考文獻

[49] 劉建慧. (2006). SPOT 衛星稀疏取樣幾何於 BRDF 模式反演之精度評估. 作物, 環境與生物資訊, 3(3), 217-228.

[7] Dymond, J. R., Shepherd, J. D., & Qi, J. (2001). A simple physical model of vegetation reflectance for standardising optical satellite imagery. Remote Sensing of Environment, 75(3), 350-359.

[10] Feng, J., Rivard, B., & Sanchez-Azofeifa, A. (2003). The topographic normalization of hyperspectral data: implications for the selection of spectral end members and lithologic mapping. Remote Sensing of Environment, 85(2), 221-231.

[12] Florinsky, I. V. (1998). Accuracy of local topographic variables derived from digital elevation models. International Journal of Geographical Information Science, 12(1), 47-62.

[13] Gao, B. C., Heidebrecht, K. B., & Goetz, A. F. (1993). Derivation of scaled surface reflectances from AVIRIS data. Remote Sensing of Environment, 44(2), 165-178.