基于高光谱壁画盐分指数的模拟壁画盐含量反演  

Inversion of Salt Content in Simulated Mural Based on Hyperspectral Mural Salt Index

作　　者：国洲乾 吕书强 侯妙乐 孙宇桐 李淑阳 崔雯漪 GUO Zhou-qian;L Shu-qiang;HOU Miao-le;SUN Yu-tong;LI Shu-yang;CUI Wen-yi(School of Geomatics and Urban Spatial Informatics,Beijing University of Civil Engineering and Architecture,Beijing 102616,China;Beijing Key Laboratory for Architectural Heritage Fine Reconstruction&Health Monitoring,Beijing 102616,China)

机构地区：[1]北京建筑大学测绘与城市空间信息学院,北京102616 [2]建筑遗产精细重构与健康监测北京市重点实验室,北京102616

出　　处：《光谱学与光谱分析》2023年第10期3272-3279,共8页Spectroscopy and Spectral Analysis

基　　金：国家自然科学基金项目(42171356,42171444);北京建筑大学研究生创新项目(PG2022111)资助。

摘　　要：壁画酥碱与盐霜主要由其所含的可溶性盐造成,具有不可逆性,严重影响壁画的健康状态,利用非接触式的高光谱技术对壁画所含可溶性盐进行定量反演具有重要意义。针对壁画盐分检测成本高、时效低、需要实地取样等问题,提出一种基于高光谱盐分指数的壁画盐含量反演模型。用黄沙土、麦秸、细麻与无水Na_(2)SO_(4)等在室内配制成不同盐含量梯度(盐土比例:0~1%)的模拟壁画样本,采用ASD-FieldSpec4HI-RES地物波谱仪进行光谱采集,将断点校正与平均后的数据建立样本光谱集,以7∶3的比例将样本集划分用于建模与预测。对原始反射率(R)进行一阶微分(R+1D)、去包络线后一阶微分(CR+1D)、倒数的对数后一阶微分(LR+1D)、Savitzky-Golay平滑后一阶微分(SG+1D)4种增强处理,将原始反射率与增强处理后的光谱数据与盐浓度进行相关分析,提取贡献度高的前三强相关波段。用最强相关波段分别进行线性拟合与抛物线拟合建立单波段回归模型。利用前三相关波段构造一种适用于壁画盐分的高光谱指数(MSI),并与归一化盐分指数(NDSI)、三种盐分指数(SI_(1)SI_(2)SI_(3))、亮度指数(BI)进行精度评估,评价指标为决定系数(R^(2))、均方根误差(RMSE)、散点拟合线的斜率与截距。结果表明:(1)随着盐浓度增加,反射光谱曲线整体先降低后升高,盐浓度在0.3%~0.6%范围内壁画样本的反射率最低。(2)壁画中Na_(2)SO_(4)敏感波段对应为1420、1940与2210 nm,在可见光范围也存在光谱响应。(3)一阶导变换后光谱与盐浓度相关性最强,R^(2)最高提升0.646。(4)R-1D-MSI反演模型精度最高,R_(C)^(2)与RMSE_(C)分别为0.857与0.116。该研究可为壁画盐含量的快速、无损检测提供新的技术手段。Disruption and salt efflorescence are mainlycaused by the soluble salts found in the mural paintings,which are irreversible and hurt the frescoes health.Quantifying the inversion of soluble salts contained in murals using non-contact hyperspectral techniques is significant.A mural salt content inversion model based on a hyperspectral salt index is proposed to address the problems of high cost,low timeliness,and the need for field sampling for mural salt detection.Indoors,mock mural samples with varying salt content gradients(salt soil ratio:0~1%)were made with yellow sandy soil and wheat straw fine hemp mixed with anhydrous Na_(2)SO_(4).The ASD-FieldSpec4HI-RES spectrometer was used for spectral acquisition.The sample spectral set was created after break pointcorrection and averaging,which was randomly divided into a calibration subset and validation subset in the ratio of 7∶3.The original reflectance(R)was subjected to four enhancement processes:first-order differentiation(R+1D),first-order differentiation after Continuum Removal(CR+1D),first-order differentiation after Logarithm Reciprocal(LR+1D),and first-order differentiation after Savitzky-Golay smoothing(SG+1D).The original reflectance and enhanced spectral data were correlated with the salt concentration,and the top three strong correlation bands with high contribution were extracted.Single-band regression models were established by linear and parabolic fitting with the strongest correlation bands,respectively.The first three correlation bands were used to create a hyperspectral mural salinity index(MSI)which was then compared to the normalized salinity index(NDSI),three salinity indices(SI_(1)SI_(2)SI_(3)),and the brightness index(BI)for accuracy evaluation.The evaluation metrics are the coefficient of determination(R^(2)),root mean square error(RMSE),and slope of the fit scatter line with intercept.The results show:(1)with the increase of salt content,the overall reflectance spectral curve first decreases and then increases.The reflectance is lowest in

关 键 词：壁画酥碱 高光谱 拟合回归 光谱指数 盐分含量 反演 

分 类 号：TP79[自动化与计算机技术—检测技术与自动化装置]