Assessment of Nigeriasat-1 satellite data for urban land use/land cover analysis using object-based image analysis in Abuja,Nigeria     

Christopher Ifechukwude Chima  Nigel Trodd  Matthew Blackett 《国际地球制图》2018,33(9):893-911

This study assesses the usefulness of Nigeriasat-1 satellite data for urban land cover analysis by comparing it with Landsat and SPOT data. The data-sets for Abuja were classified with pixel- and object-based methods. While the pixel-based method was classified with the spectral properties of the images, the object-based approach included an extra layer of land use cadastre data. The classification accuracy results for OBIA show that Landsat 7 ETM, Nigeriasat-1 SLIM and SPOT 5 HRG had overall accuracies of 92, 89 and 96%, respectively, while the classification accuracy for pixel-based classification were 88% for Landsat 7 ETM, 63% for Nigeriasat-1 SLIM and 89% for SPOT 5 HRG. The results indicate that given the right classification tools, the analysis of Nigeriasat-1 data can be compared with Landsat and SPOT data which are widely used for urban land use and land cover analysis.  相似文献   

Syn‐sedimentary salt diapirism as a control on fluvial‐system evolution: an example from the proximal Permian Cutler Group,SE Utah,USA          下载免费PDF全文

Joanne H. Venus  Nigel P. Mountney  William D. McCaffrey 《Basin Research》2015,27(2):152-182

Loading of subsurface salt during accumulation of fluvial strata can result in halokinesis and the growth of salt pillows, walls and diapirs. Such movement may eventually result in the formation of salt‐walled mini‐basins, whose style of architectural infill may be used to infer both the relative rates of salt‐wall growth and sedimentation and the nature of the fluvial‐system response to salt movement. The Salt Anticline Region of the Paradox Basin of SE Utah comprises a series of elongate salt‐walled mini‐basins, arranged in a NW‐trending array. The bulk of salt movement occurred during deposition of the Permian Cutler Group, a wedge of predominantly quartzo‐feldspathic clastic strata comprising sediment derived from the Uncompahgre Uplift to the NE. The sedimentary architecture of selected mini‐basin fills has been determined at high resolution through outcrop study. Mini‐basin centres are characterized by multi‐storey fluvial channel elements arranged into stacked channel complexes, with only limited preservation of overbank elements. At mini‐basin margins, thick successions of fluvial overbank and sheet‐like elements dominate in rim‐syncline depocentres adjacent to salt walls; many such accumulations are unconformably overlain by single‐storey fluvial channel elements that accumulated during episodes of salt‐wall breaching. The absence of gypsum clasts suggests that sediment influx was high, preventing syn‐sedimentary surface exposure of salt. Instead, fluvial breaching of salt‐generated topography reworked previously deposited sediments of the Cutler Group atop growing salt walls. Palaeocurrent data indicate that fluvial palaeoflow to the SW early in the history of basin infill was subsequently diverted to the W and ultimately to the NW as the salt walls grew to form topographic barriers. Late‐stage retreat of the Cutler fluvial system coincided with construction and accumulation of an aeolian system, recording a period of heightened climatic aridity. Aeolian sediments are preserved in the lees of some salt walls, demonstrating that halokinesis played a complex role in the differential trapping of sediment.  相似文献   

A quantitative approach to fluvial facies models: Methods and example results     

Luca Colombera  Nigel P. Mountney  William D. McCaffrey 《Sedimentology》2013,60(6):1526-1558

Traditional facies models lack quantitative information concerning sedimentological features: this significantly limits their value as references for comparison and guides to interpretation and subsurface prediction. This paper aims to demonstrate how a database methodology can be used to generate quantitative facies models for fluvial depositional systems. This approach is employed to generate a range of models, comprising sets of quantitative information on proportions, geometries, spatial relations and grain sizes of genetic units belonging to three different scales of observation (depositional elements, architectural elements and facies units). The method involves a sequential application of filters to the knowledge base that allows only database case studies that developed under appropriate boundary conditions to contribute to any particular model. Specific example facies models are presented for fluvial environmental types categorized on channel pattern, basin climatic regime and water‐discharge regime; the common adoption of these environmental types allows a straightforward comparison with existing qualitative models. The models presented here relate to: (i) the large‐scale architecture of single‐thread and braided river systems; (ii) meandering sub‐humid perennial systems; (iii) the intermediate‐scale and small‐scale architecture of dryland, braided ephemeral systems; (iv) the small‐scale architecture of sandy meandering systems; and (v) individual architectural features of a specific sedimentary environment (a terminal fluvial system) and its sub‐environments (architectural elements). Although the quantification of architectural properties represents the main advantage over qualitative facies models, other improvements include the capacity: (i) to model on different scales of interest; (ii) to categorize the model on a variety of environmental classes; (iii) to perform an objective synthesis of many real‐world case studies; (iv) to include variability‐related and knowledge‐related uncertainty in the model; and (v) to assess the role of preservation potential by comparing ancient‐system and modern‐system data input to the model.  相似文献   

Geological interpretation of current subsidence and uplift in the London area,UK, as shown by high precision satellite-based surveying     

Don Aldiss  Helen Burke  Barrie Chacksfield  Richard Bingley  Norman Teferle  Simon Williams  David Blackman  Richard Burren  Nigel Press 《Proceedings of the Geologists' Association. Geologists' Association》2014

Long term planning for flood risk management in coastal areas requires timely and reliable information on changes in land and sea levels. A high resolution map of current changes in land levels in the London and Thames estuary area has been generated by satellite-based persistent scatterer interferometry (PSI), aligned to absolute gravity (AG) and global positioning system (GPS) measurements. This map has been qualitatively validated by geological interpretation, which demonstrates a variety of controlling influences on the rates of land level change, ranging from near-surface to deep-seated mechanisms and from less than a decade to more than 100,000 years’ duration.  相似文献   

Distinct styles of fluvial deposition in a Cambrian rift basin   总被引：1，自引：0，他引：1  

Maurício G. M. Santos  Renato P. Almeida  Lucas P. S. Godinho  André Marconato  Nigel P. Mountney 《Sedimentology》2014,61(4):881-914

Process‐based and facies models to account for the origin of pre‐vegetation (i.e. pre‐Silurian) preserved fluvial sedimentary architectures remain poorly defined in terms of their ability to account for the nature of the fluvial conditions required to accumulate and preserve architectural elements in the absence of the stabilizing influence of vegetation. In pre‐vegetation fluvial successions, the repeated reworking of bars and minor channels that resulted in the generation and preservation of broad, tabular, stacked sandstone‐sheets has been previously regarded as the dominant sedimentary mechanism. This situation is closely analogous to modern‐day poorly vegetated systems developed in arid climatic settings. However, this study demonstrates the widespread presence of substantially more complex stratigraphic architectures. The Guarda Velha Formation of Southern Brazil is a >500 m‐thick synrift fluvial succession of Cambrian age that records the deposits and sedimentary architecture of three distinct fluvial successions: (i) an early rift‐stage system characterized by coarse‐grained channel elements indicative of a distributive pattern with flow transverse to the basin axis; and two coeval systems from the early‐ to climax‐rift stages that represent (ii) an axially directed, trunk fluvial system characterized by large‐scale amalgamated sandy braid‐bar elements, and (iii) a distributive fluvial system characterized by multi‐storey, sandy braided‐channel elements that flowed transverse to the basin axis. Integration of facies and architectural‐element analysis with regional stratigraphic basin analysis, palaeocurrent and pebble‐provenance analysis demonstrates the mechanisms responsible for preserving the varied range of fluvial architectures present in this pre‐vegetation, rift‐basin setting. Identified major controls that influenced pre‐vegetation fluvial sedimentary style include: (i) spatial and temporal variation in discharge regime; (ii) the varying sedimentological characteristics of distinct catchment areas; (iii) the role of tectonic basin configuration and its direct role in influencing palaeoflow direction and fluvial style, whereby both the axial and transverse fluvial systems undertook a distinctive response to syn‐depositional movement on basin‐bounding faults. Detailed architectural analyses of these deposits reveal significant variations in geometry, with characteristics considerably more complex than that of simple, laterally extensive, stacked sandstone‐sheets predicted by most existing depositional models for pre‐vegetation fluvial systems. These results suggest that the sheet‐braided style actually encompasses a varied number of different pre‐vegetation fluvial styles. Moreover, this study demonstrates that contemporaneous axial and transverse fluvial systems with distinctive architectural expressions can be preserved in the same overall tectonic and climatic setting.  相似文献   

Measurement requirements for a Near-Earth Asteroid impact mitigation demonstration mission   总被引：1，自引：0，他引：1  

Stephen D. Wolters  Andrew J. Ball  Nigel Wells  Christopher Saunders  Neil McBride 《Planetary and Space Science》2011,59(13):1506-1515

A concept for an Impact Mitigation Preparation Mission, called Don Quijote, is to send two spacecrafts to a Near-Earth Asteroid (NEA): an Orbiter and an Impactor. The Impactor collides with the asteroid while the Orbiter measures the resulting change in the asteroid's orbit, by means of a Radio Science Experiment (RSE) carried out before and after the impact. Three parallel Phase A studies on Don Quijote were carried out for the European Space Agency: the research presented here reflects the outcomes of the study by QinetiQ. We discuss the mission objectives with regard to the prioritisation of payload instruments, with emphasis on the interpretation of the impact. The Radio Science Experiment is described and it is examined how solar radiation pressure may increase the uncertainty in measuring the orbit of the target asteroid. It is determined that to measure the change in orbit accurately a thermal IR spectrometer is mandatory, to measure the Yarkovsky effect. The advantages of having a laser altimeter are discussed. The advantages of a dedicated wide-angle impact camera are discussed and the field-of-view is initially sized through a simple model of the impact.  相似文献   

A CORINE map of Great Britain by automated means. Techniques for automatic generalization of the Land Cover Map of Great Britain.     

Robin Fuller  Nigel Brown 《International journal of geographical information science》2013,27(8):937-953

Abstract

The European Commission (EC) programme ‘Co–ordination of Information on the Environment’ (CORINE) includes a project to map the land cover of member states. The CORINE map is essentially one which combines land cover and land use, giving 44 separate classes, in vector, displayed at a scale of 1:100000 with a minimum mappable unit of 25 ha. The Institute of Terrestrial Ecology (ITE) has compiled a digital land cover map of Great Britain (LCMGB) from classification of Landsat–TM data, resampled to a 25 m raster, with a minimum mappable unit of 0.125 ha and 25 cover types. This paper describes a pilot study which demonstrates the successful spatial generalisation with contextual interpretation to convert the LCMGB to CORINE specifications using semi–automated techniques within a GIS environment.  相似文献   

Paleogene crustal anatexis and metamorphism in Lhasa terrane, eastern Himalayan syntaxis: Evidence from U-Pb zircon ages and Hf isotopic compositions of the Nyingchi Complex   总被引：7，自引：0，他引：7  

Liang GuoHong-Fei Zhang  Nigel HarrisRandall Parrish  Wang-Chun XuZhang-Liang Shi 《Gondwana Research》2012,21(1):100-111

In the eastern Himalayan syntaxis, the southern Lhasa terrane is dominated by middle- to high-grade metamorphic rocks (Nyingchi Complex), which are intruded by felsic melts. U-Pb zircon dating and zircon Hf isotopic composition of these metamorphic and magmatic rocks provide important constraints on the tectono-thermal evolution of the Lhasa terrane during convergent process between Indian and Asian continents. U-Pb zircon data for an orthogneiss intruding the Nyingchi Complex yield a protolith magma crystallization age of 83.4 ± 1.2 Ma, with metamorphic ages of 65-46 Ma. This orthogneiss is characterized by positive ε_Hf (t) values of + 8.3 and young Hf model ages of ~ 0.6 Ga, indicating a derivation primarily from a depleted-mantle or juvenile crustal source. Zircons from a quartz diorite yield a magma crystallization age of 63.1 ± 0.6 Ma, with ε_Hf (t) values of − 8.2 to − 2.7, suggesting that this magma was sourced from partial melting of older crustal materials. Zircon cores from a foliated biotite granite show ages ranging from 347 to 2690 Ma, with age peaks at 347-403 Ma, 461-648 Ma and 1013-1183 Ma; their zircon ε_Hf (t) values range from − 30.6 to + 6.9. Both the U-Pb ages and Hf isotopic composition of the zircon cores are similar to those of detrital zircons from the Nyingchi Complex paragneiss, implying that the granite was derived from anatexis of the Nyingchi Complex metasediments. The zircon rims from the granite indicate crustal anatexis at 64.4 ± 0.7 Ma and subsequent metamorphism at 55.1 ± 1.3 and 41.4 ± 2.3 Ma. Our results suggest that the late Cretaceous magmatism in the southern Lhasa terrane resulted from Neo-Tethys oceanic slab subduction and we infer that Paleocene crustal anatexis and metamorphism were related to the thermal perturbation caused by rollback of the northward subducted Neo-Tethyan oceanic slab.  相似文献   

Timing of uplift and evolution of the Lüliang Mountains,North China Craton     

JunFeng Zhao  ChiYang Liu  Nigel Mountney  JianJun Lu  JiLong Cao  Yao Yang  Rui Xue 《中国科学:地球科学(英文版)》2016,59(1):58-69

This study analyses evidence for reformed basin development and basin-mountain coupling associated with development of the Ordos Basin and the Lüliang Mountains, China. Gaining an improved understanding of the timing and nature of uplift and evolution of the Lüliang Mountains is important for the reconstruction of the eastern sedimentary boundary of the Ordos Basin(a major petroliferous basin) as well as for providing insight into the evolution and breakup of the North China Craton(NCC). Based on systematic sampling for fission track analysis, it is suggested that the main phase of uplift of the Lüliang Mountains occurred since later part of the Early Cretaceous. Three evolutionary stages of uplift and development are identified: slow initial uplift(120–65 Ma), accelerated uplift(65–23 Ma), and intensive uplift(23 Ma to present), with the majority of the uplift activity having occurred during the Cenozoic. The history of uplift is non-equilibrium and exhibits complexity in temporal and spatial aspects. The middle and northern parts of the Lüliang Mountains were uplifted earlier than the southern part. The most intensive episode of uplift activity commenced in the Miocene and was associated with a genetic coupling relationship with the eastern neighboring Cenozoic Shanxi Grabens. The uplifting and evolutionary processes of the Lüliang Mountains area since later part of the Early Cretaceous share a unified regional geodynamic setting, which was accompanied by uplift of the Mesozoic Ordos Basin and development of the neighboring Cenozoic Shanxi Grabens. Collectively, this regional orogenic activity is related principally to the far-field effects of both the compression sourced from the southwestern Tibet Plateau and westward subduction of the Pacific Plate in Cenozoic.  相似文献   

北喜马拉雅淡色花岗岩地球化学: 区域对比、岩石成因及其构造意义   总被引：29，自引：1，他引：28  

张宏飞  张利  赵志丹  李德威 《地球科学》2005,30(3):275-288

北喜马拉雅出露一系列片麻岩穹窿,这些穹窿被形成于27.5～10Ma的淡色花岗岩侵入.淡色花岗岩的岩石类型为二云母花岗岩,它们的主量元素组成为SiO2=70.97%～74.54%、K2O+Na2O=6.27%～8.09%、K2O/Na2O=0.91～1.36及A/CNK=1.10～1.33.然而,它们在微量元素组成上呈现出较大的变化:Rb=(41～322)×10-6、Sr=(26～139)×10-6、Ba=(135～594)×10-6、(La/Yb)N=0.97～17.31、Eu/Eu=0.29～0.72.北喜马拉雅淡色花岗岩的主量元素和微量元素组成特征类似于高喜马拉雅中新世的二云母花岗岩,而在Ti、Mg、Ca、Ba含量和Rb/Sr比值上明显不同于高喜马拉雅中新世的电气石-白云母花岗岩.北喜马拉雅淡色花岗岩(87Sr/86Sr)t=0.7344～0.8503(t=10Ma),εNd(10Ma)=-12.5～-19.3,与高喜马拉雅淡色花岗岩无明显差异.在岩石成因上,北喜马拉雅和高喜马拉雅中新世淡色花岗岩均起因于构造减压作用,由此导致白云母发生脱水反应诱发高喜马拉雅结晶岩系的深熔.但北喜马拉雅淡色花岗岩形成的地质背景明显不同于高喜马拉雅淡色花岗岩,前者具有较长的时间跨度,开始形成于喜马拉雅渐新世的地壳增厚期,之后形成于中新世穹窿片麻岩的折返时期,而高喜马拉雅淡色花岗岩与中新世高喜马拉雅结晶岩系的构造挤出作用有关.因此,北喜马拉雅和高喜马拉雅淡色  相似文献