ELF Radar System Proposed for Localized D-Region Ionospheric Anomalies

This letter proposes a novel extremely low frequency (ELF) radar for localized D-region (altitude < 95 km) ionospheric anomalies that have been generated by natural geophysical processes. The proposed system would use the former U.S. Navy Wisconsin Transmitting Facility as a distant well-characterized impulsive ELF source. Sample calculations that demonstrate how passive vertical E-field detectors could characterize ionospheric conductivity depressions of variable diameter located above Los Angeles are provided. These calculations have been obtained using our recently developed three-dimensional whole-Earth electromagnetic wave propagation model based upon the rigorous finite-difference time-domain solution of Maxwell's equations. A key potential application of the proposed ELF radar system is the detection of hypothesized ionospheric earthquake precursors     

西秦岭金矿化带中土壤与岩石实验室光谱相关性研究

通过西秦岭金矿化带中土壤与岩石实验室光谱的相关性分析与研究。探索该区表层壤覆盖条件下应用遥感信息寻找金矿床。研究表明,土壤与岩石两者光谱之间有很高的正相关性,并且在谱形上亦有相似性,使得利用该地区土壤光谱特征从遥感信息中提取出土壤覆盖层下的岩石光谱特征成为可能,为这种遥感技术找矿方法提供依据。     

干涉雷达在DEM测量中的精度影响及处理方法

干涉合成孔径雷达 (INSAR)为数字高程模型 (DEM)测量提供了一种新的手段。它具有同时获取三维信息、测量范围广、空间和高程分辨率高等优点。文中首先扼要介绍了干涉雷达的原理 ,然后重点讨论几个影响测量精度的因素及其处理方法 ,如相关、运动补偿、配准、相位展开等。     

基岩裸露区蚀变岩遥感信息的提取方法

笔者利用与金属矿化相关的蚀变岩的TM多波段图像像元亮度值曲线的双峰特性(TM3和TM5为高值),以柳沟峡地区为样区,进行了提取蚀变岩遥感信息的方法研究,改进了Crosta信息提取方法,认为用TM1+TM2、TM4/TM3、TM5、TM7组合进行主分量分析所获得的蚀变岩遥感异常图效果最佳。将该方法用于北祁连山西段,疏勒河以东9000km2区域内蚀变岩遥感信息提取,其结果是：在103处已知矿产地中的86处有蚀变岩遥感异常信息显示,符合率达83.5%,进而预测了找矿靶区115处。     

Marine Radar Oil Spill Monitoring Technology Based on Dual-Threshold and C–V Level Set Methods

Marine radar oil spill monitoring technology has the advantages of wide-range target detection, a flexible working mode, and the ability to operate in severe weather. Based on oil spill data collected from the 7.16 accident in Dalian, China, two comprehensive oil spill monitoring methods using X-band horizontal polarized marine radar are presented. The improved Prewitt operator, Otsu algorithm, median filtering, and mean filtering were used to preprocess the original marine radar image. Subsequently, the recognition of offshore oil films were studied via the dual-threshold method and C–V level set method. Results show that the image data achieved the ideal noise reduction effect after pretreatment, and retained marine radar ocean wave information effectively. The C–V level set method required relatively lower levels of data preprocessing. However, it relied heavily on the energy-driven window by expert presupposition. It was therefore only suitable for obtaining continuous oil film information. Its calculation efficiency was related to the number of evolutions and the size of the image. The dual-threshold method required higher data preprocessing. Furthermore, the effective monitoring range of ocean waves must be determined in advance. This method could identify discrete oil film information at sea and had high computational efficiency. The dual-threshold method is better for the automatic identification of marine oil film information. The two kinds of monitoring methods described herein are useful for the identification and disposal of oil spills at sea.     

A Low-Power High-Resolution Broad-Band Radar Using a Pulse Compression Technique for Meteorological Application

A new high-resolution Ku-band Doppler radar for meteorological applications has been developed. With the new system design, the radar can accurately measure the radar reflectivity factor with 4-m resolution over a range from 40 m to several kilometers for 100-mW power using a pulse compression technique. Details of the system design, signal processing algorithm, and data acquisition procedures are described. To demonstrate the accuracy of the system, the radar reflectivity measurements are compared with the Joss-Waldvogel disdrometer measurements, and fairly good agreement is shown. The ability of the system to capture the backscattered signal and Doppler spectrum from rain volume at low altitude with high resolution is demonstrated for both convective- and stratiform-type rain events.     

Ocean Internal Wave Observations Using Space Shuttle and Satellite Imagery

Abstract

Space shuttle photographs and satellite radar (SAR) images provide an excellent view of high‐contrast ocean features such as internal waves, fronts, eddies, oil slicks, and cloud patterns which contain the signatures of atmospheric processes. Since ocean internal waves generate local currents which modulate surface wavelets and slicks, we have been able to detect packets of internal waves in space shuttle photographs and radar imagery of the Atlantic, Pacific, and Indian Oceans. A global database on internal waves has been developed at our center with support from ONR and NASA, and is accessible on the Internet. The database includes visible and radar imagery. To test the database, digitally orthorectified images were used for dynamic and statistical analysis of internal waves. In the deep ocean we found the wavelength distribution to be Gaussian while in the coastal ocean it is Rayleigh. Results have also been applied to non‐linear evolution studies of ocean internal waves, atmospheric solitary waves and to estimate ocean currents.     

SPECTRAL CORRELATIONS OF VEGETATION ASSOCIATIONS GROWING ON DIFFERENT GEOLOGICAL STRUCTURES

A method of correlating spectral signatures of vegetation with soil chemistry and, in turn, of inferring the presence of subsurface mineral deposits (oil in particular) is outlined. Variations in the content of nitrogen, sulfur, and trace elements in the soil, known to correspond, for example, with underground deposits of oil, induce changes in chlorophyll content of vegetation that are detectable on imagery in different zones of the spectrum, which upon statistical analysis can be used to predict the presence of oil in underlying strata. Translated from: Izvestiya vysshikh uchebnykh zavedeniy, Geodeziya i aerofotos'yemka, 1986, No. 4, pp. 88-93.     

简缩极化特征值分析的溢油检测

为有效利用简缩极化SAR进行海洋溢油检测,本文基于简缩极化特征值分析,提出了3个用于简缩极化溢油检测的参数,引入了基于简缩极化特征值分解的简缩极化熵Hc(Compact Polarization Entropy)、简缩极化比参数PFc(Compact Polarization Fraction)、简缩极化基准高度PHc(Compact Polarization Pedestal Height)特征进行海洋溢油检测。海表的散射类型主要为低熵散射(小粗糙面发生的Bragg散射),为弱去极化、弱散射过程随机性状态,由于溢油会阻尼海水的Bragg散射,使其熵值变高、呈去极化、强散射过程随机性状态,故简缩极化熵、简缩极化比参数和简缩极化基准高度可以用来检测海洋溢油。本文采用C波段的Radarsat-2、SIR-C/X-SAR数据进行了实验,结果表明:简缩极化熵、简缩极化比参数和简缩极化基准高度能够有效抑制疑似溢油,使海水与疑似溢油差异变小;突出溢油区域,使海水与溢油的可区分性变大。     

Internal Layer Tracing and Age&#8211;Depth Relationship From the Ice Divide Toward Jakobshavn, Greenland

Signs of long-term glaciological processes and past ice-sheet structure are preserved in the internal layer manifestations of the Greenland ice sheet. Internal layer data have been collected over a substantial portion of the Greenland ice sheet using the University of Kansas ice-sounding radar. In this letter, these layers are traced along thousands of kilometers of flight lines from the ice divide toward Jakobshavn, which is the most active glacier in Greenland. The authors determine the traced radar layers' age at the Greenland Ice Core Project (GRIP) site using the GRIP core age-depth relationship. Inasmuch as the depth varies spatially for a layer of a specific dated age, an age-depth relationship for each location along the flight lines of this letter can be found using the traced layers. Thirty-one points where flight lines cross over one another were analyzed. From the flight line crossover analysis, a 9-m maximum difference (< 1%) was found     

Altimetry with GNSS-R interferometry: first proof of concept experiment

The Global Navigation Satellite System Reflectometry (GNSS-R) concept was conceived as a means to densify radar altimeter measurements of the sea surface. Until now, the GNSS-R concept relied on open access to GNSS transmitted codes. Recently, it has been proposed that the ranging capability of the technique for ocean altimetric applications can be improved by using all the signals transmitted in the bandwidth allocated to GNSS, which includes open access as well as encrypted signals. The main objective of this study is to provide experimental proof of this enhancement through a 2-day experiment on the Zeeland Bridge (The Netherlands). In the experiment, we used a custom built GNSS-R system, composed of high gain GPS antennas, calibration subsystem, and an FPGA-based signal processor which implemented the new concepts, an X-band radar altimeter and a local geodetic network. The results obtained indicate that the new approach produces a significant improvement in GNSS-R altimetric performance.     

多普勒雷达杂波背景下的一种目标分离方法

根据目标识别算法对数据的要求，就杂波背景下的目标分离问题进行研究，并提出了一种基于小波包分析的自适应滤波算法，通过比较说明了该方法的有效性。     

Spatial analysis in a Markov random field framework: The case of burning oil wells in Kuwait

 This paper discusses a modeling approach for spatial-temporal prediction of environmental phenomena using classified satellite images. This research was prompted by the analysis of change and landscape redistribution of petroleum residues formed from the residue of the burning oil wells in Kuwait (1991). These surface residues have been termed “tarcrete” (El-Baz et al. 1994). The tarcrete forms a thick layer over sand and desert pavement covering a significant portion of south-central Kuwait. The purpose of this study is to develop a method that utilizes satellite images from different time steps to examine the rate-of-change of the oil residue deposits and determine where redistribution is are likely to occur. This problem exhibits general characteristics of environmental diffusion and dispersion phenomena so a theoretical framework for a general solution is sought. The use of a lagged-clique, Markov random field framework and entropy measures is deduced to be an effective solution to satisfy the criteria of determination of time-rate-of-change of the surface deposits and to forecast likely locations of redistribution of dispersed, aggraded residues. The method minimally requires image classification, the determination of time stationarity of classes and the measurement of the level of organization of the state-space information derived from the images. Analysis occurs at levels of both the individual pixels and the system to determine specific states and suites of states in space and time. Convergence of the observed landscape disorder with respect to an analytical maximum provide information on the total dispersion of the residual system. Received: 5 September 2000 / Accepted: 10 July 2001     

一种捷变调频斜率极性和限幅相结合的SAR抗干扰方法

针对合成孔径雷达（SAR）系统面临的场景散射等干扰无法使用传统时、空、频域技术抑制的问题,提出了一种基于线性调频（LFM）信号调频斜率极性捷变和限幅过程相结合的抗干扰方法。该方法首先在慢时间域捷变雷达发射信号的调频斜率极性,其次在接收脉冲后首先对转发的干扰信号进行匹配、限幅,然后在逆滤波之后正常成像。仿真验证了捷变方法的抗干扰性能。     

Coregistration Based on Three Parts of Two Complex Images and Contoured Windows for Synthetic Aperture Radar Interferometry

The coregistration of complex image pairs is a very important step in synthetic aperture radar interferometry (InSAR) data processing. This letter proposes a novel coregistration method that only needs three arbitrary parts of the two complex images instead of four parts in the existing coregistration methods. This method constitutes an integrated three-part method for InSAR data processing with our contoured-correlation-interferometry method for phase-image generation. Saving one part transmission makes a significant advantage when processing SAR images on satellites. Furthermore, we demonstrate that, by means of using fringe contoured windows instead of squared windows, the accuracy of the coregistration for both the three-part coregistration method and the existing methods can be improved considerably     

Consistency Analysis of Subsurface Fracture Characterization Using Different Polarimetry Techniques by a Borehole Radar

We present a fully polarimetric borehole radar in conjunction with radar polarimetry, Pauli decomposition, and H-alpha decomposition techniques to carry out physical characterization of subsurface fractures. Further tests are needed to validate the applicability of radar polarimetry analysis for physical characterization of subsurface targets. Toward this goal, we present the implementation of two other decomposition techniques, namely: (1) the Durden-Freeman decomposition and (2) polarimetric anisotropy parameter methods, in the context of previous research and examine the consistency of results using various polarimetric decomposition techniques. While results from the radar polarimetry decomposition were found to depend greatly upon the kind of physical or mathematical models, these techniques seem to provide comparable performances in terms of fracture characterization and classification.     

稀少控制的多平台星载SAR联合几何定标方法

几何定标采用地面控制点获取距离-多普勒模型中的精确几何参数,用于完成星载SAR影像高精度几何定位。但在广域范围内,特别是高山地区域,控制点极难获取。此外,传统定标方法仅面向单一平台SAR影像,尚不能实现多平台影像的联合几何定标。针对上述问题,本文提出一种基于稀少控制的多平台星载SAR联合几何定标方法。该方法从包含实测控制点的主影像出发,使用点位追踪算法获取主影像与从影像之间的连接点,并以连接点为桥梁逐级完成从影像的几何定标。本文采用京津冀地区南北向分布共计235 km的3景TerraSAR-X、3景TanDEM-X、5景高分三号影像进行联合几何定标试验,仅使用5个控制点即完成了所有影像的几何定标,并利用SF-3050星站差分GNSS接收机采集实测GPS点进行精度评价。结果表明使用稀少控制点定标后的TSX/TDX影像的几何定位精度优于3 m,GF-3影像的几何定位精度优于7.5 m,验证了该方法的有效性和正确性。     

Using Multibaseline InSAR to Recover Layovered Terrain Considering Wideband Array Problem

This letter deals with the problems of retrieving height and synthetic aperture radar (SAR) reflectivity of layovered terrain using multibaseline SAR interferometry (InSAR). In particular, we focus on the wideband array problem caused by practically large InSAR arrays and high-resolution SAR images, i.e., the problem of signal envelope misalignment, which is neglected in the work by Gini We propose two methods to eliminate or mitigate the effect of envelope misalignment, one called the aligning method and the other called the joint range cell processing method. In the aligning method, we align each signal envelope for each searched height of the layovered components (i.e., ground resolution cells with different altitudes) during searching procedure. The joint range cell processing method jointly processes the neighboring cells in range to estimate the parameters of layovered components so that the effect of the envelope misalignment can be mitigated. Theoretical analysis and computer simulation results show that both methods have the ability to provide accurate estimation of the heights and radar reflectivities of multiple layovered resolution cells in the presence of large envelope misalignments.      

Using Synthetic Aperture Radar Imagery for Flood Modelling

Airborne radar technology has traditionally been largely devoted to military applications. In recent years, applications in telecommunications, oil exploration and agriculture have proved that radar technology can also be used commercially. This paper focuses on an application of airborne radar technology in the insurance industry and describes the development of a large-scale flood risk assessment model for the River Thames. The model is based upon airborne Synthetic Aperture Radar (SAR) data and was built with commonly used Geographic Information Systems (GIS) and image processing tools. From the Orthorectified Images (ORIs) a land cover map was produced, from which a surface roughness map could be derived. A Digital Elevation Model (DEM) was processed to remove trees and other soft barriers and obtain the effective ground level. This was achieved by using standard GIS processes. The methodology may be applicable to any organisation exposed to flood risk.