Removing atmospheric MTF and establishing an MTF compensation filter for the HJ-1A CCD camera

The total image modulation transfer function (MTF) comprises imaging system MTF and atmospheric MTF, both of which can produce blurring effects in remote-sensing images. Imaging system MTF, one of the important specifications of the imaging system, is used to characterize the radiometric response of the sensor. Atmospheric MTF, which consists of aerosol MTF and turbulence MTF, usually changes with external atmospheric conditions. To obtain the MTF of the imaging system, the atmospheric MTF has to be removed from the total image MTF. This study aims to determine a method for removing the atmospheric MTF for the charge-coupled device (CCD) camera on-board the Huanjing 1A satellite (HJ-1A). The aerosol MTF and the turbulence MTF in the CCD images were first predicted based on the aerosol optical depth (AOD) derived by dark target and reanalysis of data from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR). Then, the MTFs of the CCD camera were retrieved by removing the aerosol and turbulence MTFs from the total on-orbit image MTFs that were calculated from the linear features on CCD images. For the HJ-1A CCD camera, results show that the MTF values at Nyquist frequency increased by about 10% after the atmospheric MTFs were removed. The total image MTF became degraded by about 50% when AOD was high or turbulence was strong. Furthermore, this study has established an MTF compensation (MTFC) filter for the HJ-1A by modifying the ‘modified inverse filter (MIF)’ approach. Results illustrate that the effective instantaneous field of view (EIFOV) of the restored image improved from 78 to 41 m, while the noise level of the model was well controlled. This research demonstrates that the modified approach is effective for sensors with low MTF values.     

环境一号卫星CCD相机水体信息采集特性分析

利用覆盖我国4大海区共88景图像数据,针对4波段CCD相机(HJ-1A/CCD1、HJ-1A/CCD2、HJ-1B/CCD1、HJ-1B/CCD2)在水体中的信息采集特性进行分析。结果表明:(1)HJ-1A和B星虽不是水色卫星,但其CCD相机在水体中依然有一定的信息,可作为水色遥感器服务于水环境;(2)HJ-1B/CCD1在南海海域水体信息采集过程存在明显的太阳耀斑现象,因而在水色信息提取时太阳耀斑是一个不可忽略的因子;(3)无论是在一类水体还是在二类水体,各遥感器的近红外波段皆存在水体信息采集为零的现象,其中HJ1B-CCD2尤为明显。利用近10景涵盖了HJ-1A/CCD1、HJ-1A/CCD2、HJ-1B/CCD1、HJ-1B/CCD2数据,以及同时过境的EOS/MODIS,采用基于遥感器入瞳处总辐亮度的交叉定标方法进行交叉辐射定标,获取适用于水体目标的交叉辐射定标参数。最后根据瑞利散射和气溶胶散射的计算值,以及获取的交叉定标系数,反推出HJ1B-CCD2可能接受到的灰度值。     

Spatial resolution estimation of CBERS-1 and CBERS-2 CCD cameras

Modulation Transfer Function (MTF) is a means of characterizing sensor spatial resolution and is used to measure image quality during in-flight commissioning phase. Another important parameter is the Effective Instantaneous Field of View (EIFOV), which is also used to measure system performance. This work describes three approaches to estimate the effective spatial resolution of Charge-Coupled Device (CCD) cameras aboard China–Brazil Earth Resources Satellite (CBERS)-1 and CBERS-2. These approaches use artificial and natural targets to estimate the EIFOV in across-track and along-track directions. CBERS-1 and CBERS-2 have the same specifications and carry three sensors: the Wide Field Imager (WFI), High-Resolution CCD Camera and Infrared Multispectral Scanner (IRMSS). The results obtained from these methods are compared with those of preflight measurements. The results have shown that the effective spatial resolutions in the across-track direction, for both CBERS-1 and CBERS-2 cameras, are worse than those in the along-track direction. Furthermore, it has been observed that their spatial resolutions are not consistent with the camera specifications in both directions. Although the methodologies presented here have been used to estimate the spatial resolution of CCD cameras aboard CBERS satellite, they can also be used to estimate the spatial resolution of similar sensors.     

HJ-1星CCD相机场地辐射定标与真实性检验研究

为了满足HJ-1星遥感数据定量化应用的需求,2008年10月中旬,以敦煌定标实验场为地面目标,采用反射率基法对HJ-1A和HJ-1B星的CCD相机开展场地绝对辐射定标,以确定CCD相机响应的变化,并对得到的定标结果进行了误差分析。同时利用非定标同日的敦煌场和贡格尔实验场的CCD星地同步数据得到的表观辐亮度作为标准值,对定标系数进行真实性检验研究。结果表明,定标系数模拟出的CCD表观辐亮度与标准值非常接近,误差均小于3%。研究表明:此次定标实验的结果精度高,并将两次同步数据的定标系数平均值作为定标系数结果,为CCD相机定量化应用研究奠定了良好基础。     

CBERS-02B星HR与CCD影像融合研究

CBERS-02B星搭载了高分辨率全色相机HR和多光谱传感器CCD,HR和CCD分别具有高空间分辨率和高光谱分辨率的特点。对这两类影像进行融合可以得到尽可能完整和准确的地物观测影像。对北京地区CBERS-02B的HR和CCD影像分别用HSV变换、HPF变换、Brovey变换、HIS变换、SFIM变换和小波变换等融合方法进行融合,对融合结果从空间细节和光谱保持两个方面分别定性和定量地进行评价,并比较这几种融合算法在CBERS-02B的HR和CCD遥感影像融合中的效果,得到了几种比较合适的融合方法。     

Validation of HJ-1 B charge-coupled device vegetation index products with spectral reflectance of Hyperion

To validate the HJ-1 B charge-coupled device (CCD) vegetation index (VI) products, spectral reflectance data from EO-1 Hyperion of a close date were used to simulate the band reflectance of the HJ-1 B CCD camera. Four vegetation indices (the normalized difference vegetation index (NDVI), the ratio vegetation index (RVI), the soil adjusted vegetation index (SAVI) and the enhanced vegetation index (EVI)) were computed from both simulated and actual HJ-1 B CCD band reflectance data. Comparisons between simulated and actual HJ-1 B CCD band reflectance data, as well as that between simulated and actual HJ-1 B CCD vegetation indices were implemented to validate the VI products of the HJ-1 B CCD camera. The correlation coefficients between simulated and actual HJ-1 B CCD band reflectance data were 0.836, 0.891, 0.912 and 0.923 for the blue, green, red and near infra-red bands, and the correlation coefficients between simulated and actual HJ-1 B CCD VIs were 0.943, 0.926, 0.939 and 0.933 for SAVI, RVI, NDVI and EVI. The standard deviation of differential images between actual and simulated HJ-1 B CCD VIs are 0.052, 0.527, 0.073 and 0.133. The results show that the VI products from the HJ-1 B CCD camera are consistent with the simulated VIs from Hyperion, which proves the reliability of HJ-1 B CCD VI products.     

基于HJ-1A/B卫星CCD数据的土地宏观监测试验研究

对HJ-1A/B卫星CCD数据质量进行分析,并采用人工解译和计算机自动分类两种方法进行土地利用信息提取试验研究。结果表明,HJ-1A/B卫星CCD数据能够满足制作1∶100 000比例尺数字正射影像图的平面精度要求,可用于不大于1∶100 000比例尺的土地利用宏观遥感监测。
     

星载焦面视场拼接TDI CCD相机成像质量及处理方法分析

本文分析卫星偏航角、相机积分时间、平台稳定性、姿轨误差对焦平面线阵采用视场拼接的TDI相机地面成像的影响,包括线阵、沿轨两个方向上的错位(点上的变化)与地面扫描轨迹方向上的影像畸变(线上的变化).针对CBERS-02B HR相机的卫星影像,研究地面解决偏航角引起图像错位的数据处理方法——基于地面影像的图像配准仿射变换纠正法.根据CBERS-02B HR线阵的地面配准试验,分析出了CBERS-02B卫星星上偏航角补偿精度与误差对图像质量的影响,及影像畸变产生的原因.     

一种可靠的多光谱CCD遥感图像配准方法

多源遥感图像数据的融合和后继应用必须先实现严格的配准。针对CBERS-02B遥感卫星多光谱CCD相机的成像尺寸大、像质差异性小及不同波段图像间的误差范围较固定等特点,提出一种基于小窗口多次匹配的图像配准方法。即在整幅大图像上均匀获取多个小窗口图像与基准图像进行灰度NCC匹配,将多个匹配结果通过剔除误匹配点后求平均的方法来获得具有子像素级精度的配准结果,从而保证配准的可靠性和精度。将该方法用于对多光谱CCD图像的配准实验中,结果表明本文提出的配准方法具有可行性和实用性。     

The cross-calibration of CBERS-02B/CCD visible-near infrared channels with Terra/MODIS channels

Radiometric calibration is a prerequisite to quantitative remote sensing, and its accuracy has a direct impact on the reliability and accuracy of the quantitative application of remote-sensing data. This article attempts to cross-calibrate the visible and near-infrared channels 1 (450–520 nm), 2 (520–590 nm), 3 (630–690 nm), and 4 (770–890 nm) of the China–Brazil Earth Resources Satellite (CBERS)-02B/charge-coupled device (CCD) camera with channels 3 (459–479 nm), 4 (545–565 nm), 1 (620–670 nm), and 2 (841–876 nm) of the Terra/Moderate Resolution Imaging Spectroradiometer (MODIS), respectively. The radiative transfer modelling (RTM) method is implemented using the CBERS-02B/CCD and Terra/MODIS measurements at the Dunhuang radiometric calibration site in October 2008. The differences between the cross-calibration and vicarious calibration techniques for channels 1, 2, 3, and 4 are 11.15%, –0.89%, 2.88%, and 11.28%, respectively. Furthermore, the accuracies of the cross-calibration coefficients of CBERS-02B/CCD are analysed, wherein the results indicate that the calibration uncertainty is within 5%.     

HJ-1A/1B卫星远程播报系统的实现

基于环境与灾害监测预报小卫星星座中的HJ-1A、1B卫星遥感数据,提出一种卫星影像数据与矢量数据在远程播报系统中快速叠加匹配的方法与技术流程。在此基础上,实现了HJ-1A、1B卫星宽覆盖CCD相机的数据远程播报。系统测试表明,远程播报系统对HJ-1A、1B卫星数据空间定位准确,数据处理速度快,满足远程播报实时显示数据的要求。     

利用环境一号卫星数据监测雾分布

雾是环境空气监测的一个重要内容之一。根据环境一号卫星B星（HJ-1B）的数据特点,从典型地物、云、雾的微物理特性的RT3辐射传输模拟出发,分析不同波段典型地物和云、雾的反射率、亮温差别,提出了综合利用HJ-1B卫星CCD相机和红外相机数据进行雾监测的方法与流程。最后,使用2009年3月12日我国南方地区的HJ-1B数据为卫星监测数据进行了监测试验。结果表明:HJ-1B卫星数据能够实现雾的监测,但由于薄云受到地表影响,无法准确区分薄云与雾。     

HJ-1A/1B星CCD传感器数据在黄东海浒苔监测中的应用

基于浒苔光谱特性和归一化植被指数,利用HJ-1A/1B星CCD传感器数据对黄东海浒苔进行监测。监测结果表明HJ-1A/1B星CCD传感器,可以提供比MODIS更多的精细信息,如提供重点海域的浒苔分布范围、覆盖范围、变化状况等信息。     

基于高空间分辨率的热污染遥感监测研究进展

综述了卫星遥感热红外海表温度反演原理,并对海表温度中的“皮温”和“体温”进行了界定;着重总结了热红外遥感海表温度反演的主要方法-单通道法、分裂窗法、多角度法等;详细介绍了具有较高热红外通道空间分辨率卫星传感器Landsat TM/ETM+、CBERS-02 IRMSS、ASTER、HJ-1B IRS的海表温度反演算法,并对各卫星热红外通道特点进行了对比;最后,对影响热红外温度反演精度的因素进行了简要分析,指出了目前研究存在的问题并对未来的研究方向进行了展望。     

HJ-1B卫星遥感数据在重庆市城市热环境监测的应用分析

本文以MODIS反演大气透射率,以HJ-1B/CCD分类结果反演地表比辐射率,并基于单窗算法,利用HJ-1B/IRS4数据反演地表温度.在此基础上,提取研究区的热场变异指数来分析重庆热岛空间分布特征,并就NDVI与NDBI对热岛效应的影响进行了分析.其结果如下:1)重庆城市热岛大致位于中梁山、铜锣山之间,呈东北、西南走向分布;2)热岛中心不在市中心,而是集中在大渡口工业园区、江北机场这些能耗大、人口密集区域,热岛强度范围在5?C-10?C之间;3)接近长江、嘉陵江水域的建筑用地密集区域,其热岛效应并不明显;4)NDVI与热岛强度呈负相关关系,NDBI与热岛强度呈现较为明显的正相关关系,二者对热岛都有重要影响,而NDBI的影响更大.因此,利用HJ-1B数据监测城市热环境,能较好地揭示重庆城市热岛空间分布特征,为城市环境监测与改善提供参考.     

HJ数据的LBV变换及其在面向对象分类中的应用

为了探讨环境卫星影像在分类中的应用潜力,通过对其地物光谱进行分析,计算推导出了适用于环境卫星数据的LBV变换公式,并且将变换后得到的LBV图像应用到面向对象分类中。实验结果表明:推导的针对HJ\|1B影像的LBV变换公式具有普适性,并且经过LBV变换后的影像有效地弥补了环境卫星数据光谱分辨率不高的缺点,在分割参数相同的情况下,分割效果明显好于原始影像分割结果。利用变换后的LBV图像进行面向对象分类,可以很好地提取出水体、植被、城镇和建筑用地4大类,总体分类精度达到93%,Kappa系数为0.8894,表明经LBV变换后的HJ影像在面向对象分类中具有很大的应用潜力。     

HJ-1A/B CCD与Landsat TM/ETM+植被指数的交互比较

利用5对同日过境的HJ-1A/B CCD和Landsat TM/ETM+影像对,研究了二者植被指数(NDVI,SAVI,EVI)之间的定量关系。选用其中的3对影像对作为实验影像,通过对均匀同质实验区对应的植被指数进行回归分析求出二者之间的转换方程,用未参与实验的2对影像对来验证所求转换方程的有效性,并对二者植被指数之间的差异进行了分析。结果表明：两种传感器对应的植被指数之间存在极显著的线性正相关关系,所求的转换方程具有较高的精度,可以利用转换方程将两种传感器的植被指数进行互为转换,有利于二者植被监测结果的互为补充,而两种传感器在光谱响应函数上的不同造成了二者植被指数间存在差异。     

HJ-1A/B卫星CCD影像大气订正

大气订正是遥感信息定量化研究中必不可少的一步,目前已有一些成熟的方法,但由于HJ-1A/B卫星CCD相机波段设置特点,常规的大气订正方法基本不适合于HJ-1A/BCCD影像.本文在大量分析HJ-1A/BCCD影像中不同地物的多种指数基础上,提出了改进暗目标法实现HJ-1A/BCCD影像的大气订正,该方法采用比值植被指数(RVI)、土壤调整植被指数(SAVI)和归一化水体指数(NDWI)的综合分析法确定暗像元自动提取,使之适用于环境减灾卫星CCD影像数据.为了客观地验证该方法的精度,本文选取地表平坦均一的敦煌校正场作为实验区,通过多次测量卫星过境时的地表反射率进行分析验证.     

基于二阶段算法的HJ-CCD数据过火区制图

利用环境减灾小卫星多光谱数据研究过火区的制图方法,并分析对比了4种植被指数对于过火区的分离性。结果表明:基于可见光和近红外的BAI(Burned Area Index)与GEMI(Global Environment Monitoring Index)指数对于过火区的分离能力较好。在此基础上,采用二阶段识别算法对实验区的过火区进行提取。首先采用严格的阈值提取燃烧较为严重的过火像元,并以此作为第二阶段过火区识别的“种子”点,该阶段以减少误判为目的;第二阶段采用区域生长提取其他过火区域,同时采取较为宽松的阈值作为生长准则,以减少漏判,最后得出过火区边界。精度验证结果表明:该方法提取的过火区误判率为5.5%,漏判率为12.7%。     

HJ-1卫星在港口海冰监测中的应用

以黄骅港煤炭航道海冰监测为例,采用国产环境一号卫星CCD数据,研究环境一号卫星监测海冰原理,实验环境一号卫星在煤炭航道中海冰的监测方法和流程,通过对航道、港池和锚地海冰反射率的研究,确定海冰类型,估算海冰厚度;利用经几何精纠正后的影像,统计不同海冰类型在航道、港池和锚地中的位置、范围和密集度;根据环境一号卫星日或双日的过境周期,实施了2010/2011年冬季黄骅港海冰业务化监测,从而直接为港口调度航道破冰、装船、北煤南运提供遥感技术支持。