基于多尺度相关性分析的InSAR对流层延迟误差改正算法

针对合成孔径雷达干涉技术中对流层延迟误差会影响DEM精度的问题,提出采用小波多尺度相关性分析方法来减弱与高程相关的对流层延迟误差的影响,来提高合成孔径雷达干涉DEM的估计精度。该方法基于小波多分辨率分析理论,根据差分干涉相位不同组成的频率特性,利用小波分解重构均方根误差变化率确定分解层数,降低地形残差相位、噪声相位等对大气延迟误差相位估计的干扰,提取对流层延迟误差相位所在频带;然后结合对流层延迟误差相位和雷达坐标系下的DEM在不同尺度上的相关性定权并进行降权处理,重构解缠差分干涉图,改正差分干涉相位中与高程相关的对流层延迟的影响。采用本文方法对覆盖河南义马地区的2景ENVISAT ASAR数据进行处理,得到对流层延迟误差改正后的差分干涉图,估计的与高程相关的对流层延迟相位,与地形变化情况吻合。将对流层延迟误差改正后的干涉图用于DEM高程估计,结果显示本文方法重建的DEM与Aster GDEM的标准差由30.7 m提高到26.37 m,提高了InSAR DEM估计精度。     

Development of a geotechnical and geophysical database for seismic zonation of the Ankara Basin,Turkey

The Kocaeli earthquake (M _w = 7.4) of 17 August 1999 occurred in the Eastern Marmara Region of Turkey along the North Anadolu Fault and resulted in a very serious loss of life and property. One of the most important geotechnical issues of this event was the permanent ground deformations because of both liquefaction and faulting. These deformations occurred particularly along the southern shores of ?zmit Bay and Sapanca Lake between the cities of Yalova and Adapazar? in the west and east, respectively. In this study, three sites founded on delta fans, namely De?irmendere Nose, Yeniköy tea garden at Seymen on the coast of ?zmit Bay, and Vak?f Hotel site on the coast of Sapanca Lake were selected as typical cases. The main causes of the ground deformations at these sites were then investigated. Geotechnical characterization of the ground, derivation of displacement vectors from the pre- and post-earthquake aerial photographs, liquefaction assessments based on field performance data, and analyses carried out using the sliding body method have been fundamental in this study. The displacement vectors determined from photogrammetric evaluations conducted at De?irmendere and Seymen showed a combined movement of faulting and liquefaction. But except the movements in the close vicinity of shorelines, the dominant factor in this movement was faulting. The results obtained from the analyses suggested that the ground failure at De?irmendere was a submarine landslide mainly because of earthquake shaking rather than liquefaction. On the other hand, the ground failures at the Yeniköy tea garden on the coast of Seymen and the hotel area in Sapanca town resulted from liquefaction-induced lateral spreading. It was also obtained that the ground deformations estimated from the sliding body method were quite close to those measured by aerial photogrammetry technique.     

The analysis of ground vibrations induced by bench blasting at Akyol quarry and practical blasting charts

Ground vibrations arising from excavation with blasting is one of the fundamental problems in the mining industry. Therefore, the prediction of ground vibration components plays an important role in the minimization of environmental complaints. In this study, 582 events were recorded during limestone production at a quarry (Akyol Quarry) during a period of time. The blasting parameters of these shots were also carefully recorded. During the statistical analysis of the collected data, three predictor equations proposed by the United States Bureau of Mines (USBM), Ambraseys–Hendron and Langefors–Kihlstrom were used to establish a relationship between peak particle velocity and scaled distance described by these prediction equations. As a result of this analysis, the most powerful relationship was determined and proposed to be used in this site. And also, this equation was used in the derivation of the practical blasting charts specific to this site as a practical way of predicting the peak particle velocity and maximum charge amount per delay for future blasting.     

Frequency domain electromagnetic and ground penetrating radar investigation of ephemeral streams: case study near the Southern High Plains,Texas

A frequency domain electromagnetic (FDEM) and ground penetrating radar (GPR) study was conducted on an ephemeral stream in north-central Texas to determine if FDEM and GPR measurements can be combined to determine the electrical characteristics of current and ancient stream channels. GPR data were collected at several frequencies to image sedimentary structures of different scale lengths, and to determine the formation porosity and water content of stream sediments. FDEM measurements were collected using Geonics EM31 and EM34 loop–loop instruments on a profile along the current stream channel and five profiles perpendicular to the channel. The results indicate that the greater spatial resolution of the EM31 mapped the current and possible ancient channels better than the EM34, however, the EM34 provided depth information on the formations underlying the channel sediments that the EM31 could not image. GPR measurements taken along a point bar deposit with 200, 100 and 25 MHz antennae indicated that the higher frequency antenna better resolved channel structures including laminar bedding, trough scours and cross-bedding, however, lower frequency antenna (25 MHz) imaged sedimentary structures within the underlying channel sediments. Common midpoint GPR measurements collected along the point bar deposit were used to estimate the sediment formation porosity (26%) and the water content, during a dry period, of the unsaturated (12%) and saturated (26 or 100% of the pore space) sediments. The combined results indicated that the FDEM data should be collected first because of the speed and ease of measurements. The FDEM data (especially the EM31) pointed to the locations of possible sedimentary structures, which can then be resolved by using different frequency GPR measurements.     

Reinforcing Coal Mine Roof with Polyurethane Injection: 4 Case Studies

NIOSH has recently completed a study of the interaction between polyurethane (PUR) and coal mine roof in order to determine the mechanism of reinforcement, in both highly fractured rock and unfractured rock. Four case studies of PUR reinforcement are presented. At a West Virginia site, a borehole camera revealed the location of roof voids and guided the PUR injection. By injecting polyurethane into a zone from 0.6 to 1.8 m (2–6 ft.) high in the roof, a roof beam was created and ongoing intersection falls were halted. In another highly fractured roof in a western Pennsylvania mine, a total of 5.8 cm (2.3 in.) of rubbleized rock was found in a zone up to 3 m (10 ft.) into the roof. Untargeted PUR injection filled approximately 1/2 of the fractures. These two case studies showed that it is not necessary to fill up 100% of the void space to create stability. In the other two field sites, polyurethane was injected into weak, but unfractured roof. Post-injection video monitoring showed that weak bedding planes were hydraulically wedged open and polyurethane injected along bedding. The reinforcement value of this injection method is limited because of the wafer-thin layer of PUR introduced along bedding, and the lack of a PUR “webbing” which would serve as a structural framework to provide strength. It was determined that video inspection prior to PUR injection can aid in identifying the fracture zones to target, and minimize “blind” pumping and loss of PUR.     

Variations in the accuracy of gravity recovery due to ground track variability: GRACE,CHAMP, and GOCE

Following an earlier recognition of degraded monthly geopotential recovery from GRACE (Gravity Recovery And Climate Experiment) due to prolonged passage through a short repeat (low order resonant) orbit, we extend these insights also to CHAMP (CHAllenging Minisatellite Payload) and GOCE (Gravity field and steady state Ocean Circulation Explorer). We show wide track-density variations over time for these orbits in both latitude and longitude, and estimate that geopotential recovery will be as widely affected as well within all these regimes, with lesser track density leading to poorer recoveries. We then use recent models of atmospheric density to estimate the future orbit of GRACE and warn of degraded performance as other low order resonances are encountered in GRACE’s free fall. Finally implications for the GOCE orbit are discussed.     

地质雷达特征图像与典型地质现象的对应关系

地质雷达是浅层地质勘探的有效方法,其对断层破碎带、裂隙带、富水带、岩溶洞穴等不良地质灾害有明显的异常反映。地质雷达测量方式、测线布置及系统参数的选择,可根据测量环境以及探测目标体的大致走向、规模、物性等情况综合分析,做出合理选择。通过用地质雷达对多个工区进行工程勘查,从地质雷达图像的波形、频率、振幅、相位及电磁波能量吸收情况(或自动增益梯度)等细节特征的变化规律出发,建立了典型地质现象与地质雷达特征图像的对应关系,可以作为地质雷达图像解释的重要判据。     

合成孔径雷达高度计的波形重跟踪与仿真试验分析

基于初步研究获得的合成孔径雷达高度计卷积模型,推导获得合成孔径雷达高度计波形关于时间偏移、合成上升时间、信号幅度3个参数偏导数的卷积计算公式,利用数值积分及傅里叶变换实现合成孔径高度计回波模型的重跟踪。在多个单位联合协同下,利用仿真轨道、对流层、电离层及潮汐等模型生成了合成孔径模式下的回波波形。对比表明,仿真生成的合成孔径模式下的回波波形与CryoSat-2卫星SAR模式下的回波波形整体形状一致。利用仿真波形数据进行重跟踪试验,结果表明在20Hz数据条件下(约350m分辨率),合成孔径模式下的重跟踪精度达到5cm,较之传统模式有一定的提高。     

Forest classification and impact of BIOMASS resolution on forest area and aboveground biomass estimation

The European Space Agency (ESA) is currently implementing the BIOMASS mission as 7th Earth Explorer satellite. BIOMASS will provide for the first time global forest aboveground biomass estimates based on P-band synthetic aperture radar (SAR) imagery. This paper addresses an often overlooked element of the data processing chain required to ensure reliable and accurate forest biomass estimates: accurate identification of forest areas ahead of the inversion of radar data into forest biomass estimates.The use of the P-band data from BIOMASS itself for the classification into forest and non-forest land cover types is assessed in this paper. For airborne data in tropical, hemi-boreal and boreal forests we demonstrate that classification accuracies from 90 up to 97% can be achieved using radar backscatter and phase information. However, spaceborne data will have a lower resolution and higher noise level compared to airborne data and a higher probability of mixed pixels containing multiple land cover types. Therefore, airborne data was reduced to 50 m, 100 m and 200 m resolution. The analysis revealed that about 50–60% of the area within the resolution level must be covered by forest to classify a pixel with higher probability as forest compared to non-forest. This results in forest omission and commission leading to similar forest area estimation over all resolutions. However, the forest omission resulted in a biased underestimated biomass, which was not equaled by the forest commission. The results underline the necessity of a highly accurate pre-classification of SAR data for an accurate unbiased aboveground biomass estimation.     

基于Roberts梯度与HIS色彩空间的SAR图像伪彩色编码

针对SAR灰度影像信息不丰富,不利于解译识别的问题,提出了一种基于Roberts梯度与HIS色彩空间的SAR图像伪彩色编码算法。首先,计算SAR图像的梯度图像,并确定梯度阈值T;然后,比较像素梯度与阈值的大小,大于阈值的像素按照Roberts梯度方法编码,否则按照基于HIS色彩空间方法编码;最后,对两种编码结果进行合成,得到最终伪彩色SAR图像。利用TerraSAR-X影像数据进行了实验验证,结果表明:本文研究的方法均能达到很好的伪彩色编码效果。