基于人工神经网络和AMSR2多频微波亮温的北疆地区雪深反演

被动微波遥感数据是进行积雪深度反演的重要资料,不同频率微波信号对积雪响应不同。利用人工神经网络(Artificial Neural Network,ANN)方法结合新疆北部地区积雪观测资料建立AMSR2(Advanced Microwave Scanning Radiometer 2)微波亮温(Brightness Temperature,TB)、地理位置、地形因子与雪深的隐含关系,以实现通过亮温、地理位置、地形因子估算北疆地区积雪深度,并分析微波极化方式、位置以及地形的不同组合方式对雪深反演效果的影响。实验结果表明:水平极化对雪深反演的影响大于垂直极化,纬度对雪深的影响大于经度,地表粗糙度和坡向对雪深的影响大于高程和坡度,并且位置和地形因子对雪深影响作用相当。最终通过4种优选模型的误差空间分布对比发现,综合亮温、经纬度、坡度、坡向的ANN输入模型能够较好的反映北疆地区积雪分布状况,训练集的站点平均误差在-7~6cm之间,该组合模型作为神经网络的输入能够较为合理地获取北疆地区雪深模拟值。     

基于Landsat8热红外遥感数据的山地地表温度地形效应研究

地表温度是影响地表能量收支平衡的重要参量,能够综合反演地表的水热交换过程。虽然当前在基于地表温度开展全球或者区域尺度的地表能量平衡研究方面取得一系列的进展,但是面向山地区域尺度的类似研究仍然面临较大的挑战。为分析山地复杂地形对山地地表温度时空分布的影响规律,基于具有较高空间分辨率的Landsat 8热红外数据,以我国西南典型山地为研究对象,定量反演该区域的地表温度空间分布状况,结合SRTM90DEM数据,选择从海拔、坡度和坡向3个关键地形因子角度分析山地地表温度的地形效应特征。结果发现:山地地表温度随地形因子均呈现出十分显著的变化特征。总体而言,地表温度均随着海拔和坡度的升高而降低,而在坡向方面,南坡的温度相比北坡的温度要高。在地形效应分析的基础上,通过开展1km空间尺度地形和地表温度的空间统计分析发现,山地1km尺度下地表温度存在较大的空间异质性,且其影响不可忽略。研究结果表明:开展山地地表水热过程遥感动态监测需高空间分辨率地表温度作为数据支持,以准确描述山地地形因素对地表能量交换过程的影响。     

寒区复杂地表冻融状态判别式算法改进

基于冻融土的微波辐射特征,在HUT(Helsinki University of Technology)积雪辐射模型的基础上,引入新的冻土介电常数模型计算冻/融土的介电常数,利用高级积分方程模型(Advanced Integrated Emission Model,AIEM)计算地表发射率,改进了寒区复杂地表微波辐射模型和冻融状态判别式算法。采用AMSR~2(The Advanced Microwave Scanning Radiometer 2)被动微波辐射计亮温数据和地基微波辐射计观测数据进行了地表冻融状态判别式算法精度的验证与比较。结果显示:改进后的判别式算法对冻土的判识精度有明显提升,总体判识精度在82%以上,是一种较可靠的判别模式。     

基于无人机技术的山区裸露地表微径流信息分析

为了分析低山丘陵区裸露地表微径流发育特征,将无人机航测技术应用于山区裸露地表微径流发育的调查中,获取并生成了研究区域2cm分辨率的三维倾斜和正射影像数据,采用GIS表面分析、水文分析和数理统计方法,通过坡度、坡向、高程剖面、河网分布等数据可视化分析微地形中地表表层微径流发育特征.结果表明:(1)基于无人机技术提取的数据...     

基于AMSR-E的全球陆表被动微波发射率数据集

地表微波发射率表征了地物向外发射微波辐射的能力,星载被动微波发射率估算可在宏观、大尺度上对陆表微波辐射进行整体表达,是被动微波地表参数定量反演中重要基础数据,也是在大尺度上获取陆表微波辐射特征的一种途径。本数据集利用搭载在Aqua卫星上的高级微波扫描辐射计(AMSR-E)和中分辨率成像光谱仪(MODIS)的同步观测特点,采用MODIS的地表温度和大气水汽产品数据作为输入,基于考虑大气影响的发射率估算模型,生产了全球晴空条件下AMSR-E传感器运行期间(2002年6月~2011年10月)的陆表多通道双极化微波瞬时发射率。通过产品低频无线电信号影响、数据间比对、分布统计、不同地表覆盖条件的发射率特征、频率依赖和相关性研究等开展验证性分析,结果表明:瞬时发射率的动态大、细节表达丰富,月内日变化标准差在0.02以内,其时空变化、频率依赖和相关性等符合微波理论分析和自然物理过程理解。此套数据集还包括AMSR-E全生命周期的全球陆表逐日、侯、旬、半月及月产品,可用于开展星载被动微波遥感模拟、陆面模型以及陆表温度、积雪、大气降水/水汽/可降水量等反演研究。     

基于不规则三角网格剖分的非均匀起伏月球表面SAR成像模拟

按照月球表面环形山数目和形态的统计特征,数值构造了有环形山分布的月球表面地形.按月面地形坡度非均匀分布,提出由不规则三角形网格对月面地形进行剖分来表示月面数字高程.由Kirchhoff近似给出月球表面雷达回波的计算方法,数值模拟了有环形山分布的非均匀起伏月球表面的合成孔径雷达(SAR)成像.以Apollo 15着陆点地区月球表面真实的数字高程和Clementine光学数据为例,给出了Apollo 15地区模拟的SAR图像.最后,对模拟的月表SAR图像强度进行了统计验证,并与真实的月表SAR图像做了比较.     

CIVCO地形校正模型的改进及其应用

在地形复杂的山区,地形效应造成了地物的光谱特征扭曲,严重地影响了地物的识别与分类。地形校正不仅能提高遥感识别与分类的精度,还是各种定量化遥感应用的前提。CIVCO模型是一种基于统计的经验地形校正模型,原模型中阴坡和阳坡需要手工选取,且校正效果随坡度而异。通过利用太阳方位角和坡向简化了阴坡和阳坡的选取,并按照坡度分级,分别求出校正系数。在模型改进的基础上,选择黑河上游祁连山区的TM影像和相应的DEM数据进行试验,结果表明,与C模型及原模型相比,改进的模型取得了更好的校正效果。     

被动微波遥感反演土壤水分进展研究

在地球系统中, 地表土壤水分是陆地和大气能量交换过程中的重要因子, 并对陆地表面蒸散、水的运移、碳循环有很强的控制作用, 大面积监测土壤水分在水文、气象和农业科学领域具有较大的应用潜力。被动微波遥感是监测土壤含水量最有效的手段之一, 相比红外与可见光, 它具有波长长, 穿透能力强的优势, 相比主动微波雷达, 被动微波辐射计具有监测面积大、周期短, 受粗糙度影响小, 对土壤水分更为敏感, 算法更为成熟的优势。然而微波辐射计观测到的亮温除了受土壤水分影响外, 还要考虑如植被覆盖、土壤温度、雪覆盖以及地形、地表粗糙度、土壤纹理和大气效应以及地表的异质性等其它因子的影响。目前, 已研究出许多使用被动微波辐射计反演土壤水分的方法,这些方法大部分是围绕着土壤湿度与亮温温度之间的关系进行, 同时也考虑其它各种不同因子对 地表微波辐射的影响。从介绍被动微波反演地表参数的原理入手, 重点介绍被动遥感反演土壤水分当前的算法进展、研究趋势等。     

晋西黄土区坡面尺度土壤水分分布规律研究

采用定位观测方法对晋西黄土丘陵沟壑区坡面土壤水分的分布规律进行研究。结果表明:坡向、坡度、坡位是坡面尺度土壤水分分布的重要影响因素,得出了不同立地条件土壤水分的剖面变化与时间动态规律,在此基础上对不同立地条件进行聚类,给出坡面尺度下不同立地条件的分类结果,通过分类,我们可以用立地因素代替土壤水分状况,为黄土高原植被建设提供科学的土壤水分依据。     

卫星遥感影像数据的地形影响校正

地形影响校正是遥感影像辐射校正的主要内容，是获得地表真实反射率的必不可少的一步。本文提出的方法中，将6S大气校正模型与数字高程模型（DEM）结合起来，计算出水平地面上接收到的直接辐射与漫射辐射，并采用一个简单公式将其转化到地形坡面上，从而实现了对地面的辐射能量校正，同时，6S模型对卫片还进行了大气改正，可输出卫片在大气层底部的辐射亮度与反射率；然后将基于坡面的反射率换算到其在水平面上的对应值，即实现了对反射率的地形影响校正。在我们所实施的“滇金丝猴保护项目”的植被研究中，应用本方法对梅里雪山区域的ETM＋影像进行了校正，大大减小了地形对遥感数据的附加影响。     

Retrieve Snow Depth of North of Xinjiang Region from ARMS 2 Data based on Artificial Neural Network Technology

Based on the characteristics of the microwave signal responding to the snow depth，we use AMSR2 brightness temperature，geo\|location and terrain factor as the inputs of ANN，and snow depth as the desired output to develop an efficiency snow depth retrieve model.We compared the influence of combinations of TB，geo-ocation and terrain factors on the retrieve of snow depth.It is reviewed in this article that，TB of horizontal polarization，latitude perform better than vertical polarization and longitude respectively.Combination of slope and aspect is superior to other combinations of terrain factors.Besides，there are equivalent influence on snow depth of geo\|location and terrain factors.Finally，we compare the performance of four optimal ANN models under different input combinations.At last，we found that the ANN consists TB，latitude，longitude，slope and aspect as inputs is the best model which might fairly simulating the snow depth of Beijiang.     

Evaluation of terrain effect on microwave radiometer measurement and its correction

We develop a new technique for terrain correction of coarse resolution satellite microwave radiometer measurements using the high-resolution digital elevation model (DEM). With the high-resolution DEM and a facet model, we first simulated the terrain influences that resulted from both effects of local incidence and polarization rotation (PR) on the microwave radiometer measurements at the different scales of the radiometer footprints. The emissivity signals of bare surfaces are more sensitive on incidence and PR than vegetated surfaces. So the emissivities at different incidence angles of the bare surface generated by the advanced integral equation model (AIEM) were used to simulate the terrain effects on the satellite measurements. It was found that (1) the PR effect at the satellite footprint can be corrected using the absolute mean PR angle from all facets within the footprint, and (2) the satellite measurements can be described as from a mean incidence angle. Both angles can be obtained from all facets within the footprint with the high-resolution DEM and the satellite viewing geometry. Therefore, a corresponding terrain-correction technique was developed for satellite brightness temperature measurements. We also demonstrate the terrain effects on the satellite measurements from the advanced microwave scanning radiometer–earth observing system (EOS) (AMSR-E).     

Attitude-based dynamic and kinematic models for wheels of mobile robot on deformable slope

Deformable slope is a type of terrain that wheeled mobile robots (WMRs) and ground unmanned vehicles (GUVs) may have to traverse to accomplish their mission tasks. However, the associated terramechanics for wheels with arbitrary posture is rarely studied. In this paper, based on wheel attitude, dynamics of the wheel–terrain interaction for a rigid wheel on deformable slope is investigated. Through introducing the angular geometry of wheel attitude into terramechanics theory, a generalized dynamic model is developed, involving two inclination angles of slope and three attitude angles of wheel steering axis. Two representative cases are studied: the wheel runs straight forward and perpendicular to the slope, and the wheel is in a steering maneuver with an inclined steering axis. A generalized kinematic model for wheel–terrain contact point and wheel center is also provided, which analytically explicates that trajectory of wheel motion is coupled with wheel attitude while driven by angular rates. The proposed attitude-based models are valid for arbitrary wheel–terrain geometry and can lead to control purpose directly. Effectiveness of the models is confirmed by simulating the influences from attitude to wheel mechanics and motion.     

Use of digital terrain data in the interpretation of SPOT-1 HRV multispectral imagery

Abstract

This paper describes the complementary use of digital terrain information and SPOT-1 HRV multispectral imagery for the study and mapping of semi-natural upland vegetation. A digital terrain model was derived for a 10 by 10 km study area in southern Snowdonia, Wales, and was used to generate slope and aspect images. A model was developed as a first-order approximation of changes in radiance with local topography, assuming Lambertian behaviour of vegetation canopies. The model was implemented for the study area to assess its use in suppressing the effects of relief on scene radiance. Subsequently the model was refined to describe non-Lambertian reflectance.     

Airborne Experiment of TG-2 Multi-angle Polarization Imager for Cloud Phase Identification

Multi\|angle polarization measurement technology can be used to detect cloud and aerosol information,and it barely depends on prior temperature information.In order to verify capability of cloud phase classification from the TG\|2 Multi\|angle Polarization Imager developed independently by China,the results of first airborne observation experiment of Multi\|angle Polarization Imager for cloud observations were compared with the results of numerical simulation under typical conditions.The libRadtran model simulation shows that the water cloud has the maximum polarized radiation (primary rainbow) for scattering angles near 140°.The results based on radio sounding and microwave radiometer show that there are water cloud under 3.7 km height of the research area.Meanwhile,the Multi\|angle Polarization Imager accurately captures the character of maximum polarized radiation of water cloud droplet (primary rainbow) near 140° scattering angles.In addition,the corresponding MODIS observation data also shows there exists a large scale of water cloud near the research area.Above results comprehensively indicate the Multi\|angle Polarization Imager has the function of cloud phase recognition without relying on prior information,and this test lays the foundation for the further study of the space\|based polarization observations of cloud phase.     

Application to GF-2 Satellite for Road Landslides Monitoring

Global warming has profoundly changed extreme weather events,and remote sensing technology is gradually being applied to the monitoring of ecological and environmental disasters.China is one of the countries with most serious natural disasters in the world.With the development of human society and the improvement of people’s awareness of disaster risk,geological disaster monitoring and risk management has attracted more and more attention.Taking the Adjacent Area of Changsha \| Xiangtan(CXAA),which is the main part of Xiangtan jiuhua economic development zone,as the research area,the road slope and the ecological environment in the area were monitored by using the fusion image of high spatial resolution remote sensing of GF\|2 made in China on March 27,2016.Taking normalized difference vegetation index(NDVI),terrain slope index,soil index and other parameters as inputs,the comprehensive evaluation of ecological environment in CXAA was obtained by simulating the comprehensive factors of ecological environment with the comprehensive index method.We found that the ecological environment of 78.75 % of the study area was good,which indicated that the natural ecological environment on both sides of the road and the surrounding areas was basically not damaged.The road surface,water area(such as Xiangjiang river),construction land(such as Xiangtan high\|speed railway north station) and industrial areas(such as Geely automobile,Tidfore enterprise group,etc.) and other regions of the ecological environment comprehensive index is poor,on both sides of the road in some slope sections still exist the potential risk of landslide.Therefore,we suggest that during the rainy season,there is a need for more time\|phase high spatial resolution of GF-2 remote sensing satellite and other domestic GF satellite continuous monitoring,in order to more fully understand the risk of road slope landslide and provide early warning.     

地形对蚀变信息光谱影响研究与应用

通过加入地形因子进行相关光谱信息分区来提取蚀变信息,首先利用ASTER影像立体像对提取DEM,进行地形(坡向)划分,即分为阳坡、半阳坡、半阴坡、阴坡4类型,将相对应的区域统计其波谱信息,分为不同的波谱区,然后分别用主成分分析法提取蚀变信息。结果表明:波谱分区蚀变信息提取方法能够更加有效地识别出各个波谱区的蚀变异常信息,有效减小地形因素对蚀变信息提取结果的影响,并且在研究区得到很好的应用。     

TOPO III: a FORTRAN program for terrain analysis

TOPO III is a FORTRAN program that operates with rectangular arrays of equally spaced elevations, producing lists of terrain parameters (coordinates, elevation, average and maximum relief, average and maximum slope, azimuth of maximum slope, and topographic shape: slope, ridge, valley, knob, sink, saddle), point-frequency distributions of maximum and average slope, symbolic slope maps, frequency distributions of areas comprising contiguous points with the same topographic shape, and topographic shape maps with point-frequency distributions of shape types. The program compares a central elevation with interpolated elevations around the perimeter of a circular “window”, and the radius of the window may be increased in successive passes through the array. The results have been used for slope studies, for analysis of terrain factors in environmental studies, and for terrain classification.     

An integrated approach to geometric precision processing of spaceborne high-resolution sensors

The plantmetric errors due to terrain relief and atmospheric refraction must be considered when high geometric resolution sensors and off-nadir viewing angles are used. This paper presents an approach to correct these errors using an integrated procedure that takes into account geometric and radiometric effects, connected to simulations of future remote-sensing systems or precision data processing. A diagram shows the relation between the root mean square error of the digital elevation model necessary to correct the terrain relief effect and the achievable scale of the output image map. The procedure is currently applied to the SPOT simulation on the Basilicata test site in southern Italy. A short example is given to analyse the geometric errors involved.     

Geomorphometric processing of digital elevation models

The general system of geomorphometry is composed of elevation, derivatives of elevation at a point, and moments of the distribution of elevation over some area. All of the point measures in this system can be obtained by computer processing of a digital elevation model (DEM), and they can be used as input to the analysis and classification of terrain. A suite of FORTRAN programs implementing this system for dense grid DEMs has been designed and used in various operating environments. Attention has been given to the methods used in the approximation of terrain concepts such as slope and relief. An area of high relief in subarctic Canada is used to illustrate the discussion.