一种有效计算大气红外辐射传输效应的方法

红外辐射在大气中的传输特性对红外成像仿真研究具有重要意义.本文以红外辐射的传输理论为基础,综合考虑大气分子的吸收、散射,气象条件以及海拔高度等因素,提出了一种以大气条件为基本参数,计算红外成像仿真中大气光谱透过率的方法,并对算法进行了仿真实现;通过对不同条件下计算结果的分析,表明用该算法得出的结论与实际红外成像的规律基本相符,且可以满足实时性和准确性的要求,能够增强红外成像仿真的可信度,具有很好的应用价值.     

基于MODIS数据的典型能见度条件下大气透过率计算

现有的辐射传输模型仅考虑气溶胶影响下的大气透过率，在能见度低于5km时，会给大气透过率计算带来较大的误差。本文综合考虑影响大气透过率的气溶胶和水汽因素，并利用中光谱分辨率MODIS（moderate resolution imaging spectmradiometer）数据，在特征参数的空间及时间尺度变化均比较大时，对大气透过率进行了定量反演，并进一步建立了整层大气透过率与行星反照率的关系模型，为近地层大气能见度的遥感监测提供了方法。     

红外目标模拟器校准装置构建和校准技术研究

在对传统红外目标模拟器校准装置分析的基础上，结合辐射照度校准理论、方法和误差来源三方面，构建了红外目标模拟器校准装置，开展了辐照度测量系统内部杂散辐射建模仿真和抑制的研究、红外大气传输修正方法的研究和测试结果数据拟合算法的研究，分别提出了基于复合蒙特卡洛法的内部杂散辐射数学模型、基于编码器-解码器结构的卷积神经网络红外辐射大气传输校准算法和基于粒子群优化的极限学习机算法，并在实验室条件下进行了辐照度计量校准实验。分别验证了在追迹光线数相等的情况下复合蒙特卡洛法的精度更高，复合蒙特卡洛法标准偏差为6.1940×10-8，平均误差为0.19293，且仿真结果体现了红外辐射计各部分杂散辐射对探测器入瞳面接收到的杂散辐射造成的影响；基于编码器-解码器结构的卷积神经网络算法能够较好的预测大气透过率和大气程辐射，在三个波段下的平均误差为3.0783%，3.8186%，5.3452%，低于传统方法，降低了大气透过率和大气程辐射的影响；通过与GA-ELM模型、ELM模型进行对，验证了与传统数据拟合方法相比，基于PSO-ELM的方法在1μm~3μm、3μm~5μm、8μm~14μm三个波段下的拟合精度都有所提高，决定系数分别为0.9925、0.9913、0.9814，平均相对误差分别为0.1242%、0.7157%、0.7471%有效提高了红外辐射测量准确度。     

大气水汽的红外遥感

本文讨论了利用差分吸收法来遥感大气中的水汽。水汽透过率用辐射计测量，水汽含量由我们自行编制的红外辐射大气透过度计算程序的计算。在此同时还观测了气象参数，以确定光路上的水汽含量。     

舰船红外图像的传输与识别

研究舰船红外制导技术,在海平面上进行图像传输识别,由于海天背景下的红外图像目标与背景对比度较差,噪声大,所以图像边缘模糊.针对目标识别困难问题,提出了一种改进的中值滤波方法,通过计算机仿真,研究了海上舰船红外图像的传输与识别问题.根据红外辐射在大气传输中的特性和舰船的红外辐射特性,对红外辐射大气传输的舰船红外图像用改进的中值滤波方法进行预处理.最后,对预处理后的图像进行了拉普拉斯锐化处理.通过仿真结果证明,红外辐射大气传输的舰船红外图像的识别精度高,图像清晰,可以满足实时识别目标的要求.     

HJ-1B卫星热红外通道在轨绝对辐射定标

利用青海湖水面辐射校正场对HJ-1B卫星热红外通道进行绝对辐射定标,由CE312热红外辐射计测量水面辐亮度,结合辐射传输模型MODTRAN4.0计算大气透过率和上行程辐射,同时进行CE312通道与HJ-1B卫星热红外通道光谱匹配,计算传感器入瞳处等效辐亮度值。通过2010年8月1日和5日两组传感器入瞳等效辐亮度值和卫星通道计数值回归得到该卫星通道绝对定标系数,并使用内蒙达里湖水面辐射校正场2010年6月29日实测数据对定标结果进行检验。     

卫星遥感数字图像的非均匀大气修正研究

总结了各种传统卫星遥感数字图像的大气修正方法。讨论了逐点计算卫片像元的大气程辐射遥感值和大气光谱透过率的方法和原理，并在此基础上提出一个适合于非均匀大气的、包括大气程辐射和大气光谱透过等修正内容的卫星遥感数字图像广义大气修正模式。     

大气辐射传输组件的设计与实现

MODTRAN软件作为大气辐射传输计算主要的工具,主要有两种使用方式,第一种方法利用MODTRAN制作查找表,然后利用插值的方法得到输出量,虽然在速度上较快,但精度上难以保证;第二种方法直接使用MODTRAN源代码可以保证计算的精度,但很难使用在不同的编程语言中.针对以上问题,提出了一种以组件技术为基础的大气辐射传输模型的建模方法,根据大气辐射传输算法功能要求,设计了组件对外接口,实现了大气辐射传输组件,并对其进行测试.结果表示,采用该方法可以很好地解决上述问题,大气辐射传输组件不仅具有计算精度高,而且还具有可复用性和可扩展性,易与其它语言进行混合编程.被广泛应用于反演地球大气参数与开发遥感成像仿真系统.     

一个从ASTER数据中反演地表温度的劈窗算法

根据EOS/Terra多传感器的特点,提出了一个适合于ASTER数据的劈窗算法,该算法包括两个必要的参数大气透过率和比辐射率。大气透过率是通过利用MODIS的3个近红外波段反演大气水汽含量并根据大气水汽含量与热红外波段的统计关系计算得到。由于MODIS和ASTER是在同一颗星上,这种大气透过率估计方法保证了地表温度反演过程中所需大气参数的同步获取。对于比辐射率则是通过分类和JPL提高的光谱库获得。最后用大气模拟校正法对算法进行了验证,在比辐射率已知的情况下,当使用大气模型模拟得到的大气透过率时,对Planck函数优化简化后的平均精度为0.56℃;当大气透过率是从大气水汽含量计算得到时,优化平均精度为0.58℃,表明该算法可行。     

舰船目标光学特性模型构建

为了给舰船光学特性研究和可探测性研究提供理论基础。为了建立舰船目标光学特性模型。采用BRDF理论分析和计算中的微面元分析法,利用3D MAX软件将舰船表面划分为许多可计算三角形微面。在计算每个三角形微面的散射特性时,选用双向分布函数中适合计算的Cook-Torrance模型。并通过坐标转换将太阳-目标-探测器统一到面元坐标系下以及利用面元几何可见性进行消隐简化了计算量。在计算入瞳处的辐亮度时,分析了大气中分子、分子和气溶胶粒子对可见光散射的影响。最后得到了大气通过率与波长的计算公式。通过分析每个三角形微面在入瞳处的辐亮度,得到了入瞳辐亮度与波长的关系。最后建立了舰船目标光学特性模型,并通过仿真,计算了不同波长下的大气透过率以及入瞳处辐亮度。     

基于MODIS 影像数据的劈窗算法研究及其参数确定

劈窗算法是目前由热红外遥感数据获取陆面温度的主要方法。在介绍劈窗算法的一般表现形式的基础上, 我们推导出适合于MOD IS 影像数据的劈窗算法。大气透过率和地表比辐射率是求解地表温度的两个关键参数。由于MOD IS 图像分辨率较低,MOD IS 像元主要由水面、植被和裸土3种地物类型构成, 故可依据这3 种地物的构成比例确定地表比辐射率。从遥感影像上反演大气的水汽含量, 再根据大气水汽含量与大气透过率的关系计算出大气透过率。最后将文中推导的劈窗算法用于江苏省地表温度的反演。反演出来的地表温度图显示出明显的地表温度空间差异、城市热岛效应和不同的地物类型。     

An O2-A Band Atmospheric Correction Algorithm for Tower-based Platform based on Look-up Table

Tower-based spectral observation is an important connecting bridge between flux sites and satellite remote sensing data，and the effect of atmospheric absorption and scattering between horizontal surface and tower-based platform on the atmospheric absorption band such as O2-A is difficult to ignore.Firstly，the influence of atmospheric radiation transfer on the up-welling radiance and down-welling irradiance of the tower-based platform is analyzed，and the atmospheric correction method of based on upward and downward transmittance is established，that is，the influence of the upwelling radiance and down-welling irradiance is corrected by the direct transmittance and the total transmittance.Secondly，using the simulation data of MODTRAN model，the influence of AOD550 and radiative transfer path length on atmospheric transmittance is quantitatively analyzed，and the LUT of AOD550 is established based on the ratio of down-welling irradiance of near-infrared and red bands and solar zenith angle，as well as the upward and downward atmospheric transmittance LUT based on the AOD550 and the radiative transfer path length.Finally，using the canopy spectral data of different growth stages observed by the tower-based platform，the difference of the apparent reflectance between the inside and outside of the O₂-A band absorption line before and after atmospheric correction was analyzed.The results show that the atmospheric correction method based on LUT of AOD550 and radiative transfer path length proposed in this paper can better correct the influence of upwelling radiance and down-welling on the O₂-A absorption band of the tower-based platform，and provides important method support for applications such as SIF observation on the tower platform.     

基于暗原色先验的图像快速去雾

针对雾天图像饱和度和对比度较低,提出一种基于暗原色先验和透射率权值的改进算法。估计大气光的取值范围,根据该范围确定大气光值,通过判定因子区分出暗原色失效区域;对该区域透射率进行基于透射率权值因子的调整;采用快速引导滤波细化透射率,并结合大气散射模型恢复图像。该算法能在去雾过程中对可调参数进行自适应选取。实验结果表明,该算法效率较高,且复原的图像细节丰富、颜色自然,视觉效果提升的较为明显。     

基于Simulink的数模混合电路仿真平台设计与实现

针对数模混合电路仿真精度与性能之间的矛盾问题和仿真工业级复杂数模混合电路时仿真工具存在主流芯片和电路模块不足问题,提出了一种粘合模式的数模混合仿真平台模型架构,基于该架构设计并实现了一种基于Simulink软件,通过嵌入数字电路和模拟电路主流仿真引擎获得充足主流芯片和电路模块支持的数模混合电路仿真平台,设计了一种结合了拓扑排序算法的仿真控制方式,实现了对工业级复杂电路进行流程化、模块化的数模混合仿真;最后通过一个能够时序上可以逻辑拆分的典型数模混合电路仿真验证了仿真平台的有效性。     

A practical split‐window algorithm for retrieving land‐surface temperature from MODIS data

This paper presents a practical split‐window algorithm utilized to retrieve land‐surface temperature (LST) from Moderate‐resolution Imaging Spectroradiometer (MODIS) data, which involves two essential parameters (transmittance and emissivity), and a new method to simplify Planck function has been proposed. The method for linearization of Planck function, how to obtain atmosphere transmittance from MODIS near‐infrared (NIR) bands and the method for estimating of emissivity of ground are discussed with details. Sensitivity analysis of the algorithm has been performed for the evaluation of probable LST estimation error due to the possible errors in water content and emissivity. Analysis indicates that the algorithm is not sensitive to these two parameters. Especially, the average LST error is changed between 0.19–1.1°C when the water content error in the simulation standard atmosphere changes between ?80 and 130%. We confirm the conclusion by retrieving LST from MODIS image data through changing retrieval water content error. Two methods have been used to validate the proposed algorithm. Results from validation and comparison using the standard atmospheric simulation and the comparison with the MODIS LST product demonstrate the applicability of the algorithm. Validation with standard atmospheric simulation indicates that this algorithm can achieve the average accuracy of this algorithm is about 0.32°C in LST retrieval for the case without error in both transmittance and emissivity estimations. The accuracy of this algorithm is about 0.37°C and 0.49°C respectively when the transmittance is computed from the simulation water content by exponent fit and linear fit respectively.     

基于遥感卫星图像的ATCOR2快速大气纠正模型及应用

在卫星遥感成像过程中,由于气溶胶和大气中分子吸收和散射的作用,造成数据质量下降甚至变化,以至于极大地影响着遥感信息的提取和参数反演的精度。越来越多的研究表明:大气纠正将成为遥感理论和应用研究中的重要组成部分,能极大地提高卫星遥感数据在质量和时间系列的完整性。介绍一种适用于空间分布的快速大气纠正模型ATCOR2(A Spatially-Adaptive FastAtmospheric Correction-2),详细介绍模型的算法、模块结构和计算流程,讨论参数文件的结构和意义,并通过一个实例给出ATCOR2模型运行的结果。     

Geo-atmospheric processing of airborne imaging spectrometry data. Part 2: Atmospheric/topographic correction

A method for the radiometric correction of wide field-of-view airborne imagery has been developed that accounts for the angular dependence of the path radiance and atmospheric transmittance functions to remove atmospheric and topographic effects. The first part of processing is the parametric geocoding of the scene to obtain a geocoded, orthorectified image and the view geometry (scan and azimuth angles) for each pixel as described in part 1 of this jointly submitted paper. The second part of the processing performs the combined atmospheric/ topographic correction. It uses a database of look-up tables of the atmospheric correction functions (path radiance, atmospheric transmittance, direct and diffuse solar flux) calculated with a radiative transfer code. Additionally, the terrain shape obtained from a digital elevation model is taken into account. The issues of the database size and accuracy requirements are critically discussed. The method supports all common types of imaging airborne optical instruments: panchromatic, multispectral and hyperspectral, including fore/aft tilt sensors covering the wavelength range 0.35-2.55 w m and 8-14 w m. The processor is designed and optimized for imaging spectrometer data. Examples of processing of hyperspectral imagery in flat and rugged terrain are presented. A comparison of ground reflectance measurements with surface reflectance spectra derived from airborne imagery demonstrates that an accuracy of 1-3% reflectance units can be achieved.     

Infrared sensing of sea surface temperature from space

Error sources in infrared remote sensing of sea surface temperature are discussed, e.g., imperfect transmittance models, uncertain or unknown atmospheric pressure-temperature-humidity vertical profiles, temperature discontinuities at the air-sea interface, temperature differences between surface and bulk water, and neglect of surface emissivity and reflectance. Some of these are analyzed using a simplified version of the transmittance function of Prabhakara et al. (1974). The rms error in conventional sea surface temperature retrievals, in which computers are used to integrate the equation of radiative transfer over many atmospheric layers, has thus far been reduced to about ±1 K (Maul, 1980). This error is for optimum conditions, and seems irreducible. Unless the accuracy can be improved it seems impractical to spend so much effort on lengthy computer retrievals. Prabhakara et al. (1974) have devised a much simpler retrieval method using three infrared bands, which yields an rms error of ±1.1 K. A very simple method yielding ±1.0 K with two infrared bands is described here.     

Development of a Positioning Technique for an Urban Area Using Omnidirectional Infrared Camera and Aerial Survey Data

This paper describes an outdoor positioning system for vehicles that can be applied to an urban canyon by using an omnidirectional infrared (IR) camera and a digital surface model (DSM). By means of omnidirectional IR images, this system enables robust positioning in urban areas where satellite invisibility caused by buildings hampers high-precision GPS measurements. The omnidirectional IR camera can generate IR images with an elevation of 20–70° for the surrounding area of 360°. The image captured by the camera is highly robust to light disturbances in the outdoor environment. Through the IR camera, the sky appears distinctively dark; this enables easy detection of the border between the sky and the buildings captured in white due to the difference in the atmospheric transmittance rate between visible light and IR rays. The omnidirectional image, which includes several building profiles, is compared with building-restoration images produced by the corresponding DSM in order to determine the self-position. Field experiments in an urban area show that the proposed outdoor positioning method is valid and effective, even if high-rise buildings cause satellite blockage that affects GPS measurements.     

卫星影像大气校正中气溶胶模型的影响分析-以天津地区为例

基于大气校正中常用的大气辐射传输模拟软件6S模型,探讨了不同气溶胶模型对卫星影像大气校正的影响及其适用性问题。选取我国环境小卫星星座HJ\|1的CCD传感器数据,以天津地区大气污染和较清洁条件下的卫星影像为例,基于6S进行大气校正,定量估算了气溶胶模型选取对大气校正精度的影响。与此同时,通过地面太阳-天空辐射计实测,获得研究区域整层大气气溶胶参数进行大气校正,并与基于气溶胶模型的校正结果进行对比,得到以下结论:①6S气溶胶模型中,大陆型与海洋型的校正结果比较接近,而城市型气溶胶模型由于含有较高的煤烟成分比例,其校正结果与前两种相差较大;②天津地区在大气污染情况下,适合应用大陆型气溶胶模型进行大气校正,而在大气较清洁的情况下可选择海洋型气溶胶模型。
