Structural and remote sensing studies of the southern Betsimisaraka Suture, Madagascar

An assessment of the southern Betsimisaraka Suture (B.S.) of southeastern Madagascar using remote sensing and field investigation reveals a complex deformation history. Image processing of Landsat ETM+data and JERS-I Synthetic Aperture Radar (SAR) imagery was integrated with field observations of structural geology and field petrography. The southern B.S. divides the Precambrian basement rocks of Madagascar in two parts. The western part includes Proterozoic rocks whereas the eastern part is an Archean block, named the Masora block. The southern part of the B.S. includes high-grade metamorphic rocks, recording strong deformation and has mineral deposits including chromite, nickel, and emerald, characteristic of oceanic material that is compatible with a suture zone.Large-scale structural features indicate ductile deformation including three generations of folding (F1, F2, and F3) associated with dextral shearing. The first folding event (F1) shows a succession of folds with NE striking axial planes. The second folding event (F2) mainly has north–south striking axial planes and the last event (F3) is represented by mega folds that have ENE–WSW axial plane directions and have NNW and SSE contractional strain patterns. Closure of the Mozambique Ocean between two components of Gondwana sandwiched rocks of the B.S. and formed upright folds and shortening zones which produced N–S trending lineaments. Later dextral movements followed the contraction and formed NW–SE trending lineaments and N–S trending normal faults associated with dextral strike slip faults and fractures.     

Neotectonic activity of the Bomdila Fault in northeastern India from geomorphological evidences using remote sensing and GIS

One of the major geological structures across the Brahmaputra valley, which stretches from the Eastern Himalayas up to the Naga Hills, is the Bomdila Fault. Parts of the courses of the rivers – the Brahmaputra, Dhansiri (south-S), Bargang and many others – are aligned along this structure. The influence of this structure on the courses of these rivers has been studied in detail using topographic maps, satellite data and field evidences. The signatures obtained such as: (a) an unusually linear course of the lower part of the Dhansiri (S) river from Golaghat up to Dhansirimukh, (b) the abandonment of the westerly course of the earlier Dhansiri (S) river (flowing through Kaziranga) towards the present NW direction by avulsion, (c) knick bends in the MBT–MCT and Naga Thrust of Belt of Schuppen, (d) a linear 15 m high topographic scarp on the left bank of the Dhansiri (S) near Numaligarh and (e) an anomalous SE–NW trending course of the Brahmaputra from Dhansirimukh up to Hartamuli along with the parts of the rivers Buroi and Bargang on the north in the same trend infers the influence of a fault-type structure. Since all these linear segments of the rivers align along the NW–SE trending Bomdila Fault, it infers the influence of the later on the courses of these rivers. The neotectonic activity along this fault might have caused the linear high scarp and abandonment of earlier river courses.     

Shape analysis and multispectral classification in geological remote sensing

This paper discusses the usage of mathematical morphology in image processing of remotely-sensed data for geologic interpretation. Particular attention is given to noise-reducing transformations of spectral bands before and after different methods of classification, and to the usage of textural context. The development of a viable processing strategy requires a multidisciplinary approach and expert knowledge in different areas: (a) geology, geomorphology, and vegetation in a study area, (b) properties of the sensor for imagery photointerpretation, (c) spectral/spatial properties of the digital data within an integrated dataset (remote sensing and ancillary data), and (d) data-processing tools including mathematical morphology theory. Examples of geometric characterization of Canadian LANDSAT scenes are described in which shape measurements are obtained using a PC-based hybrid image-processing and geographic information system, termed ILWIS, which was developed at ITC, in the Netherlands. Classes from supervised and unsupervised classification are compared to guide in geological mapping. Classes over individual occurrences of broad vegetation-landform units are studied to aid in environmental mapping. Field knowledge is the context necessary to construct expert procedures to drive sequences of data-processing steps toward a target result such as optimal classification, enhancement, or feature extraction. The interaction between expert rules and the image-processing steps can be based on synthetic measurements of shape to quantize the information either spatially or spectrally. Many useful geometrical transformations of spatially-distributed data are extensions or generalizations of spatial analysis functions typical of geographic information systems.     

Synoptic and remote sensing analysis of dust events in southwestern Iran

Southwest regions of Iran, due to dry environmental and climatic conditions, have been identified as one of the five major regions in the world. In recent years, large parts of Iran have been affected by suspended particles from the dust storms. The studied area is located in foothills of the Zagros Mountain Range just north of Persian Gulf in southwest of Iran. Dust and other meteorological data were prepared in 3-hour intervals from 12 synoptic weather stations. For tracking dust storms, satellite images of MODIS were used. Atmospheric conditions during the occurrence of dust storms were determined using NCEP reanalysis data. According to the statistical calculations, most storms occurred in the spring and summer. The lowest number of dust events occurred in the fall and winter particularly in December and January, when there are high possibilities of rainfall occurrence and dynamical instability conditions in the north and west of the region. The results illustrated that the highest amounts of hourly dust occurred in the afternoon and the lowest amounts occurred at 00UTC (3.30 am local times). It seems that it is closely related to the heating surface and the occurrence of local dry instabilities. Analyses of data showed that dust amounts (or volumes) in all the stations have two climactic peaks, first between 1982 and 1990 and second between 2005 and 2008 periods. These peaks can be related to a variety of factors including anthropogenic factors such as war, agricultural activities, dam construction, and widespread droughts.     

Weighted model-based clustering for remote sensing image analysis

We introduce a weighted method of clustering the individual units of a segmented image. Specifically, we analyze geologic maps generated from experts’ analysis of remote sensing images and provide geologists with a powerful method to numerically test the consistency of a mapping with the entire multidimensional dataset of that region. Our weighted model-based clustering method (WMBC) employs a weighted likelihood and assigns fixed weights to each unit corresponding to the number of pixels located within the unit. WMBC characterizes each unit by the means and standard deviations of the pixels within that unit and uses the expectation-maximization algorithm with a weighted likelihood function to cluster the units. With both simulated and real data sets, we show that WMBC is more accurate than standard model-based clustering. Specifically, we analyze Magellan data from a large, geologically complex region of Venus to validate the mapping efforts of planetary geologists.     

Mapping Neogene and Quaternary sedimentary deposits in northeastern Brazil by integrating geophysics,remote sensing and geological field data

Neogene and late Quaternary sedimentary deposits corresponding respectively to the Barreiras Formation and Post-Barreiras Sediments are abundant along the Brazilian coast. Such deposits are valuable for reconstructing sea level fluctuations and recording tectonic reactivation along the passive margin of South America. Despite this relevance, much effort remains to be invested in discriminating these units in their various areas of occurrence. The main objective of this work is to develop and test a new methodology for semi-automated mapping of Neogene and late Quaternary sedimentary deposits in northeastern Brazil integrating geophysical and remote sensing data. The central onshore Paraíba Basin was selected due to the recent availability of a detailed map based on the integration of surface and subsurface geological data. We used airborne gamma-ray spectrometry (i.e., potassium-K and thorium-Th concentration) and morphometric data (i.e., relief–dissection, slope and elevation) extracted from the digital elevation model (DEM) generated by the Shuttle Radar Topography Mission (SRTM). The procedures included: (a) data integration using geographic information systems (GIS); (b) exploratory statistical analyses, including the definition of parameters and thresholds for class discrimination for a set of sample plots; and (c) development and application of a decision-tree classification. Data validation was based on: (i) statistical analysis of geochemical and airborne gamma-ray spectrometry data consisting of K and Th concentrations; and (ii) map validation with the support of a confusion matrix, overall accuracy, as well as quantity disagreement and allocation disagreement for accuracy assessment based on field points. The concentration of K successfully separated the sedimentary units of the basin from Precambrian basement rocks. The relief–dissection morphometric variable allowed the discrimination between the Barreiras Formation and the Post-Barreiras Sediments. In addition, two units of the latter (i.e., PB1 and PB2) previously mapped in the field were promptly separated based on Th concentration. A regression analysis indicated that the relationship between geophysical and geochemical values obtained for the PB1, PB2 and Barreiras Formation is significant (R-squared = 0.91; p-value <0.05). Map validation presented a high overall accuracy of 84%, with a coefficient of quantity disagreement of 12% and a coefficient of allocation disagreement of 8%. These results indicate that the methodology applied in the central onshore Paraíba Basin can be successfully used for mapping the Barreiras Formation and Post-Barreiras Sediments in other areas of the Brazilian coast. The ability to rapidly and precisely map these units using such methodology could reveal their geographic distribution along the northeastern coast of Brazil.     

Application of multi-scale remote sensing imagery to detection and hazard analysis

To both collect terrain data rapidly and save labor costs, the present study employs high-spatiotemporal-resolution imaging through Formosat-2 and aerial photography through unmanned aerial vehicles. In daily visits to the same area, images taken by Formosat-2 can be employed as data for long-term observation. Unclouded images from 2006 to 2010 processed with a false-color overlay and calculated of the normalized difference vegetation index are selected as terrain data. Aerial photos taken by unmanned aerial vehicles are utilized ground-truth data. These two types of data are analyzed to proceed with supervised classification. The results reveal that in the study area mangroves are the most exuberant in summer. The growth of mangroves in Sihcao Wetland remained in dynamic equilibrium from 2006 to 2010 without any sharp increase or decrease in quantity. This proposed method is believed to be suitable to investigate and preserve mangroves by long-term image monitoring and to avoid any unnatural influence on these conservation areas.     

闽江南北港冲淤变迁遥感动态监测与分析

基于多期次遥感影像数据,应用图像差值法、光谱特征差异法、波段替换法对闽江南北港进行冲淤变迁遥感动态监测,综合分析冲淤变迁剧烈程度可划分为3个区间,依次是南港上段,变迁最大,其次是南港下段和北港,系人为因素引起。运用遥感解译分析其变迁情况,具有高效、准确等动态监测优势,为闽江综合整治提供科学依据。     

Applications of remote sensing in geology

Geologie en Mijnbouw -     

矿山遥感编图中的高分辨率遥感数据选择与比例尺计算方法

通过对青海调查矿区多种高分辨率卫星数据处理后形成的图像进行解译和编图,掌握了合理选择遥感数据信息源、利用制图软件计算遥感影像图比例尺及编制野外调查和成果解译图的技术方法。得出在选择遥感数据时要考虑不同数据的技术参数、性价比及调查区面积;明确了当图像的出图分辨率确定后,其比例尺与图像的空间分辨率、像素大小、文档大小有直接关系,同时建立了计算遥感图像最佳比例尺和最佳出图比例尺的公式和方法;介绍了利用Photoshop和Mapgis软件,编制矿山野外调查用图和遥感解译成果图件的流程及方法。这些工作的完成对青海矿业开发地质环境效应调查起到了积极的指导作用,也充分体现了高分辨率遥感图像在工作条件艰苦地区的优势作用。     

基于IHS变换的重力异常与遥感影像融合的构造信息提取研究

本文以深部探测关键仪器装备野外实验与示范基地为例,利用影像融合技术进行地质构造信息的提取。在卫星遥感和重力异常数据空间配准的基础上,利用IHS数据融合方法,将重力异常与ETM+数据进行融合与分析。研究表明:一方面构造形迹在遥感图像及重力异常上的表征是存在差异性的,即其空间分布特征,另一方面通过卫星遥感在地表定位重力异常所反演的地质信息,能够为深部探测仪器装备野外实验选点提供科学的依据。     

Advances in microwave remote sensing of the ocean and atmosphere

This article reviews the current state-of-the-art and future prospects of the microwave techniques for remote sensing of the earth’s atmosphere and ocean. Geophysical parameters and their relationship with measured thermal microwave radiation is established through radiative transfer processes. The atmospheric temperature profile obtained from microwave sounding unit (msu) onboardtiros-N series of satellites is operational and is used for numerical weather prediction. The demonstrated applications of scanning multichannel microwave radiometer (smmr) onboard most recent and advancedseasat satellite are highlighted.The capability ofseasat active sensors for monitoring ocean parameters have also been indicated. Feasible applications of microwave techniquese.g. moisture profile with advanced moisture sounder (amsu), and surface pressure from multifrequency active microwave pressure sounder (mps) are also described. Finally the recent and advanced microwave limb sounding (mls) technique and its applications to upper atmospheric research has been reviewed.     

神经网络敏感性分析及其在遥感影像分类中的应用

针对基于连接权的神经网络敏感性分析方法中求取敏感性系数的不稳定性,提出一种优化连接权的神经网络敏感性分析方法。首先采用遗传算法根据误差最小化原则对神经网络进行优化,在优化的神经网络模型上进行基于连接权的敏感性分析。以1个数值模拟实例和华盛顿广场地区的遥感图像地物分类为例,验证所提方法的有效性。实验结果表明,所提方法求取输入变量的敏感性系数是稳定有效的,能有效筛选出遥感图像中对分类贡献较大的特征波段,达到降维的同时提高分类精度。     

卫宁北山地区遥感找矿地质异常信息提取及分析

以ETM＋影像为基础数据,采用去干扰异常主分量门限化技术提取卫宁北山地区遥感矿化蚀变异常信息,结果表明：羟基异常主要分布在铜铁沟—岔梁子—平湖滩一带,自北向南沿构造破碎带呈带状结构,一二三级异常均有,且与已知矿（化）点吻合较好;铁染异常分布面积小,主要为三级异常,在色井沟和红石堆,异常以片状沿沟谷自北向南呈带状分布,与已知矿点对应少,示矿作用不明显。结合SPOT5数据,对研究区进行＂线、环、带、色、块＂找矿五要素遥感地质构造解译。以断层和褶皱轴线为主的线要素大多呈近EW向分布;环形构造7个,推测位于金场子的环有可能由隐伏岩体引起;带要素2条,位于金场子西部,呈EW走向;色要素分布面积小且零散;未解译出块要素。根据获取的地质异常信息,建立遥感示矿模型,结合地质分析,圈定了3个遥感示矿异常区。     

航天遥感信息提取技术方法与地质遥感技术在植被覆盖地区的找矿应用

简述宽波段或高光谱遥感技术方法及亚象元、低概率目标探测技术的研究及应用现状。结合大兴安岭地区矿产资源勘查的背景条件，系统阐述该技术在植被覆盖地区地质找矿的应用流程。这一研究方案的实施及可能获得的成果，将改善在植被覆盖地区的地质找矿工作。     

基于典型相关分析的遥感影像变化检测

多通道遥感影像由于通道之间相关性的影响,相对于单通道影像的变化检测更为困难,因此需要有效的集中分布在各个通道上的变化信息,构造出不同时相之间的差异影像,以便于变化信息的分析解译。针对多通道变化信息集中的难点和通道之间相关性的影响难以消除的问题,引入多元统计分析中的典型相关分析方法,将2个时相的多通道遥感影像示作2组多元随机变量,采用多元变化检测变换,对多个波谱通道上的所有差异信息或变化信息进行重组,分配到一组互不相关的结果变量中,最大限度地消除通道间的相关性对变化检测的不利影响,初步解决了差异影像构造的问题。     

Developments in budget remote sensing for the geosciences

Acquiring outcrop, landform or other surface topography data in the field for the geosciences has always been challenging. Accessibility is often a problem, time is usually limited and an ideal spatial and temporal coverage often has to be compromised to be more manageable. However, emerging technologies, and some re-inventions of rather older ones, can overcome many of these constraints in a very exciting and budget-friendly manner. This article briefly introduces and reviews four major recent developments in budget remote sensing, specifically the use of blimps, kites, drones or UAVs (including quadcopters), and structure from motion (SFM) software. Both scientific and applied case studies are given and some possibilities for future studies are highlighted. Overall, the potential for these technologies to revolutionise the geosciences is clear and should be opportunistically embraced by scientists, resource and hazard managers and educators alike.