149 research outputs found

    Image Station Matching, Preprocessing, Spatial Registration and Change Detection with Multi-Temporal Remotely-Sensed Imagery

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    A method for collecting and processing remotely sensed imagery in order to achieve precise spatial co-registration (e.g., matched alignment) between multi-temporal image sets is presented. Such precise alignment or spatial co-registration of imagery can be used for change detection, image fusion, and temporal analysis/modeling. Further, images collected in this manner may be further processed in such a way that image frames or line arrays from corresponding photo stations are matched, co-aligned and if desired merged into a single image and/or subjected to the same processing sequence. A second methodology for automated detection of moving objects within a scene using a time series of remotely sensed imagery is also presented. Specialized image collection and preprocessing procedures are utilized to obtain precise spatial co-registration (image registration) between multitemporal image frame sets. In addition, specialized change detection techniques are employed in order to automate the detection of moving objects

    A geomorphological investigation of lateral spreading and translational sliding within the Storegga Slide

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    Lateral spreading and translational sliding are two of the most prevalent types of slope failures within the Storegga Slide. This has been concluded from a thorough analysis of three acoustic data sets from the Storegga Slide complex – high-resolution multibeam bathymetry, TOBI sidescan sonar imagery and 3D seismic data.We have applied quantitative geomorphometric techniques to the bathymetry data set and analysed the texture of sidescan sonar images using Grey-Level Occurrence Matrices (GLCMs). Both techniques have been shown to improve the geological interpretation of submarine environments (e.g. Micallef et al., 2006), and allowed an objective characterisation of the slide surface to be carried out. These results were then combined with the interpretation of the seismic data set and all the geological information currently available for Storegga in the literature. In this way we were able to define the types and boundaries of the different styles of mass movements, and represent them on a geomorphological map. Further insight is provided into the origin and the mode of failure of lateral spreading and translational sliding. Finally we attempt to describe the characteristic morphology of lateral spreading and demonstrate that it is a very common slope failure process in the Norwegian margin.peer-reviewe

    Green vegetation cover has steadily increased since establishment of community forests in Western Chitwan, Nepal

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    Community forests have been established worldwide to sustainably manage forest ecosystem services while maintaining the livelihoods of local residents. The Chitwan National Park in Nepal is a world-renowned biodiversity hotspot, where community forests were consolidated in the park’s buffer zone after 1993. These western Chitwan community forests stand as the frontiers of human–environment interactions, nurturing endangered large mammal species while providing significant natural resources for local residents. Nevertheless, no systematic forest cover assessment has been conducted for these forests since their establishment. In this study, we examined the green vegetation dynamics of these community forests for the years 1988–2018 using Landsat surface reflectance products. Combining an automatic water extraction index, spectral mixture analysis and the normalized difference fraction index (NDFI), we developed water masks and quantified the water-adjusted green vegetation fractions and NDFI values in the forests. Results showed that all forests have been continuously greening up since their establishment, and the average green vegetation cover of all forests increased from approximately 30% in 1988 to above 70% in 2018. With possible contributions from the invasion of exotic understory plant species, we credit community forestry programs for some of the green-up signals. Monitoring of forest vegetation dynamics is critical for evaluating the effectiveness of community forestry as well as developing sustainable forest management policies. Our research will provide positive feedbacks to local community forest committees and users

    Increased soluble phosphorus loads to Lake Erie: unintended consequences of conservation practices?

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    Cumulative daily load time series show that the early 2000s marked a step-change increase in riverine soluble reactive phosphorus (SRP) loads entering the Western Lake Erie Basin from three major tributaries: the Maumee, Sandusky, and Raisin Rivers. These elevated SRP loads have been sustained over the last 12 yr. Empirical regression models were used to estimate the contributions from (i) increased runoff from changing weather and precipitation patterns and (ii) increased SRP delivery (the combined effects of increased source availability and/or increased transport efficiency of labile phosphorus [P] fractions). Approximately 65% of the SRP load increase after 2002 was attributable to increased SRP delivery, with higher runoff volumes accounting for the remaining 35%. Increased SRP delivery occurred concomitantly with declining watershed P budgets. However, within these watersheds, there have been long-term, largescale changes in land management: reduced tillage to minimize erosion and particulate P loss, and increased tile drainage to improve field operations and profitability. These practices can inadvertently increase labile P fractions at the soil surface and transmission of soluble P via subsurface drainage. Our findings suggest that changes in agricultural practices, including some conservation practices designed to reduce erosion and particulate P transport, may have had unintended, cumulative, and converging impacts contributing to the increased SRP loads, reaching a critical threshold around 2002

    Creating and curating an archive: Bury St Edmunds and its Anglo-Saxon past

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    This contribution explores the mechanisms by which the Benedictine foundation of Bury St Edmunds sought to legitimise and preserve their spurious pre-Conquest privileges and holdings throughout the Middle Ages. The archive is extraordinary in terms of the large number of surviving registers and cartularies which contain copies of Anglo-Saxon charters, many of which are wholly or partly in Old English. The essay charts the changing use to which these ancient documents were put in response to threats to the foundation's continued enjoyment of its liberties. The focus throughout the essay is to demonstrate how pragmatic considerations at every stage affects the development of the archive and the ways in which these linguistically challenging texts were presented, re-presented, and represented during the Abbey’s history

    Analyzing Accuracy Attributes of Landsat and Digital Terrain Tape Data in the Context of a Digital Geobase Information System

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    The major conclusions reached in this research effort are: 1) Landsat derived land cover classification data are, at present, a marginally accurate data source for county-level resource management requirements; and 2) the accuracy of standard product National Cartographic Information Center (NCIC) Digital Terrain Tape data appear to be questionable, again with respect to the information requirements of county level resource managers. Data representation accuracy has been analyzed for Landsat/MSS land cover and NCIC Digital Terrain Tape data. Lands at derived data correctly represented land cover in 71.5% of 200 randomly sampled grid cells verified against low-altitude photography. Only 61% of the sampled Digital Terrain Tape elevation values were within one-half of the contour interval (30.5 meters) on a 1:24,000 scale topographic map. The analysis here has been specifically designed around a digital, fixed-grid geobase information system. System attributes were oriented towards county level resource management usage. Results from this study indicate that for the geographic area and objectives of this research: 1) Landsat classification data are suitable as a first stage sample of land cover for county level resource management assessments; and 2) Digital Terrain tape data are inaccurate in portraying absolute elevations, but may be effective in supplying derived graphic or terrain data products, as well as in supplying additional channels of data for the land cover classification procedure

    The effect of training strategies on supervised classification at different spatial resolution." Photogrammetric Engineering and Remote Sensing 68

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    Abstract Three different training strategies often used for supervised classification-single pixel, seed, and block or polygon training-are compared in this paper. The range parameter of semi-variograms obtained from sample image subsets of each land-uselland-cover class was used to measure the autocorrelation level during training set selection. Eight training sets with different sizes were generated and then applied to image subsets with three multispectral bands and variance texture images in the classification of six land-use classes. The classification results using these training sets were compared at five resolution levels and were based on six Color Infrared Digital Orthophoto Quarter Quadrangle (DOQQ) subsets of different urban land types in urban and rural fringe areas of the San Diego metropolitan area. The performance of different training strategies is shown to be influenced by the training size, the image resolution, and the degree of autocorrelation inherent within each class. Training approaches had more impact on classification results at fine resolution levels than at coarse resolutions. For spectrally homogeneous classes, a spatially independent, single-pixel training approach is preferred. But for spatially heterogeneous classes, small block training has the advantage of readily capturing spectral and spatial information and reduces the amount of interaction time for the analyst
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