Estimating surface ice velocity on Chhota Shigri glacier from satellite data using Particle Image Velocimetry (PIV) technique

Information about the surface ice velocity is one of the important parameters for Mass balance and Glacier dynamics. This study estimates the surface ice velocity of Chhota Shigri glacier using Landsat (TM/ETM+) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer) temporal data-sets from a period of 2009 to 2016 and 2006 to 2007, respectively. A correlation based Particle Image Velocimetry (PIV) technique has been used for the estimation of surface ice velocity. This technique uses multiple window sizes in the same data-set. Four window sizes (low, medium, high, very high) are used for each image pair. Estimated results have been compared with the published data. The outcomes attained from the medium window size closely matches with the published results. The estimated mean surface ice velocities of medium window size are 24 and 28.5 myr^?1 for 2009/2010 and 2006/2007 images pair. Highest velocity is observed in middle part of the glacier while lowest in the accumulation zone of the glacier.     

An improved building detection approach using L-band POLSAR two-dimensional time-frequency decomposition over oriented built-up areas

The objective of this study is to efficiently extract detailed information about various man-made targets in oriented built-up areas using polarimetric synthetic aperture radar (POLSAR) images. This paper develops an improved approach for building detection by utilizing Two-Dimensional Time-Frequency (2-D TF) decomposition. This method performs outstandingly in distinguishing between man-made and natural targets based on the isotropic behaviors, frequency-sensitive responses, and scattering mechanisms of objects. The proposed method can preserve the spatial resolution and exploit the advantages of TF decomposition; specifically, the exact outlines of buildings can be effectively located, and more types of features (e.g., flat roofs, roads, and walls that are oblique to the radar illumination) can be distinguished from forests in complex built-up areas by 2-D TF decomposition. The coarser-resolution subaperture images that are produced in the azimuth direction, which correspond to different looking angles, are beneficial for detecting man-made structures with main scattering centers oriented at oblique angles with respect to the radar illumination. In the range direction, the obtained subaperture images, which correspond to various observation frequencies, can be helpful in distinguishing flat roofs and roads from forests. This method was successfully implemented to analyze both NASA/JPL L-band AIRSAR and L-band EMISAR data sets. The building detection results of the proposed method exhibit a significant improvement over those of other methods and reach an overall accuracy over 80%, with approximately 20% higher than the accuracies of K-means clustering and the entropy/alpha-Wishart classifier and approximately 10% higher than the accuracy of the support vector machine method. Moreover, building details can be precisely detected, obliquely oriented buildings can be identified, and the distinction between buildings and forests is significantly improved, as both visually and statistically indicated. This method is highly adaptable and has substantial application value.     

Sentinel-1A SAR影像及其在矿区地面沉降监测中的应用研究

详细介绍了Sentinel-1A SAR影像数据的基本参数、工作模式、应用领域等。利用2016.11.09—2017.03.09的5景Sentinel-1A C波段SAR影像数据进行矿区地面沉降监测试验。基于SARscape利用双轨D-In SAR技术进行差分干涉处理,得到了研究区地面沉降分布图,直观地再现了研究区在2016.11.09—2017.03.09的沉降分布、沉降量级等。结果表明济宁某矿区在监测期间地面相对稳定,未有大面积和大量级的地面沉降发生,4个干涉对监测到的最大沉降都未超过3 cm。     

基于GAMMA的D-InSAR技术在矿区地面沉降监测中的应用

详细介绍了专业的雷达数据处理软件GAMMA和基于GAMMA的双轨D-InSAR数据处理流程;对济宁地区真实L波段的ALOS PALSAR数据进行了双轨D-InSAR处理,完成了从干涉数据的读取到形变图生成的整个流程,并生成了一系列清晰的结果图;结合GIS软件得到研究区的沉降位置、分布和沉降量等信息。研究表明:利用GAMMA软件可以对雷达影像进行双轨D-InSAR处理,得到清晰的中间结果图;双轨D-InSAR可以对矿区进行地面沉降监测,进而掌握由于煤矿开采引起的地面沉降分布和沉降程度,为煤矿区的合理开采和可持续发展提供一定的理论依据。     

A new method to determine the gravity field of small bodies from line-of-sight acceleration data

We present a new method to derive line-of-sight acceleration observables from spacecraft radio tracking data. The observables can be used to estimate the mass and gravity of a natural satellite as a spacecraft flyby. The corresponding observation model adapts to one-way and two/three-way tracking modes. As a test case for method validation and application, we estimated the mass and degree two gravity field for the Martian moon Phobos using simulated tracking data when the spacecraft Mars Express flew by Phobos on 2013 December 29. We have a few real tracking data during flyby and they will be used to confirm raw data simulation. The main purpose of this paper is to demonstrate the method of line-of-sight acceleration reduction from raw tracking data and the feasibility to estimate mass and gravity of a natural satellite using this type of observable. This novel method is potentially applicable to planet and asteroid gravity field studies combined with Doppler tracking data.     

地基干涉雷达IBIS-S桥跨结构振动变形测量与模态分析

地基雷达干涉测量技术能够以较高的时空采样频率获取线性结构目标整体瞬时变形状态。本文将该技术引入大型桥梁桥跨结构的振动变形测量与模态分析中。对动静载试验过程中的武汉二七长江大桥东岸桥跨结构开展连续变形监测,利用频域分解法计算桥跨结构的自振频率、阻尼比和模态振型。计算结果表明,地基干涉雷达干涉测量技术能够快速探测桥跨结构竖弯模态,特别适用于灾后大型线形结构健康状态的应急检测。     

GNSS-R DDM波形仿真的时延与多普勒间隔研究

DDM波形是GNSS-R技术用于反演地球物理参量的基本观测量,其仿真结果的可靠性直接影响GNSS-R的理论研究及项目工程参数设计。利用GREEPS仿真软件分析了时延间隔与多普勒间隔对DDM波形仿真结果可靠性的影响,得到了用于获取可靠DDM仿真波形的时延与多普勒间隔参数。研究表明,时延和多普勒间隔越小,DDM仿真波形与理论波形吻合度越高;当时延间隔取1/16个GPS L1 C/A码元、多普勒间隔取50 Hz时,DDM仿真波形与理论波形几乎完全吻合,二者的相关系数大于0.99;时延间隔对DDM仿真波形峰值位置的影响远大于对峰值信噪比的影响;而多普勒间隔对DDM仿真波形峰值位置与信噪比的影响相当。     

雷达遥感六十年：四个阶段的发展

雷达遥感问世60年来已经历了4个阶段的发展,其在对地观测中的作用正日益凸显,已经广泛应用于不同领域。4个阶段分别是单波段单极化阶段,多波段多极化阶段,极化和干涉阶段,以及以双/多站或星座、高时序高分宽幅、3维成像为代表的新阶段。本文结合作者长期在雷达遥感领域的研究经历,总结和回顾了雷达遥感的阶段发展和具有里程碑式的代表性技术;从观测技术、数据处理和应用角度阐述了新阶段雷达遥感的发展趋势,以及雷达遥感与人工智能和大数据结合的思考;最后着眼未来,介绍了月基雷达对地观测平台的前瞻性研究。     

利用多面函数拟合和欧拉矢量法建立福建省GPS速度场模型

通过处理福建省卫星导航定位基准服务系统(FJCORS)2013-2015年观测资料,获得GPS站实测运动速度值,在此基础上,分别利用多面函数拟合法和欧拉矢量法构建了福建省及周边区域GPS速度场模型.内符合精度方面,多面函数拟合的速度精度南北分量为1.06 mm/a、东西分量为2.00 mm/a;欧拉矢量法得到的速度精度南北分量为1.36 mm/a、东西分量为1.22 mm/a.外符合精度方面,两种方法模拟得到的检核点速度值与实测速度值的较差均在±2.28 mm/a以内.在福建省陆域内,两种方法得到的速度场具有高度的一致性,运动速度均为35 mm/a左右,运动方向为SE-E向.     

SAR image despeckling with a multilayer perceptron neural network

Speckle noise in synthetic-aperture radar (SAR) images severely hinders remote sensing applications; therefore, the appropriate removal of speckle noise is crucial. This paper elaborates on the multilayer perceptron (MLP) neural-network model for SAR image despeckling by using a time series of SAR images. Unlike other filtering methods that use only a single radar intensity image to derive their parameters and filter that single image, this method can be trained using archived images over an area of interest to self-learn the intensity characteristics of image patches and then adaptively determine the weights and thresholds by using a neural network for image despeckling. Several hidden layers are designed for feedforward network training, and back-propagation stochastic gradient descent is adopted to reduce the error between the target output and neural-network output. The parameters in the network are automatically updated in the training process. The greatest advantage of MLP is that once the despeckling parameters are determined, they can be used to process not only new images in the same area but also images in completely different locations. Tests with images from TerraSAR-X in selected areas indicated that MLP shows satisfactory performance with respect to noise reduction and edge preservation. The overall image quality obtained using MLP was markedly higher than that obtained using numerous other filters. In comparison with other recently developed filters, this method yields a slightly higher image quality, and it demonstrates the powerful capabilities of computer learning using SAR images, which indicate the promising prospect of applying MLP to SAR image despeckling.