The aim of this paper is to remark possibilities to use WorldView-2 imagery for coastline extraction. Applications are conducted on a Phlegrean area in the Campania Region (Italy): the considered range of coastline is particularly interesting because it shows two typologies of shoreline including reefs interspersed with segments of sandy beach. Two indices are used: Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI).To enhance geometric resolution of the results pan-sharpening is applied so as to obtain maps with the same pixel dimensions of the panchromatic data. To solve the problem of thresholds determination that typically affects the classification, Maximum Likelihood method based on training sites is adopted to distinguish bare soil and sea water. Best results are given by NDWI and, comparing the resultant coastline with that obtained with visual interpretation of images, shifts of less than 1 m outcome from pan-sharpened data.
In the last decades, combinations of natural and human factors\ud have resulted in extensive morphological changes to our coastlines and in\ud many cases have amplified erosion. In order to limit these changes and their\ud impact on coastal zone, it is important to plan specific actions; for this\ud purpose detailed cognizance of coastal zone is necessary. Different and\ud heterogeneous data such as historical and recent maps, remotely sensed\ud images and topographic survey result very useful to reconstruct temporal\ud shoreline changes. In this study the attention is focalized on Domitian coastal\ud zone (Italy), which is one of the most emblematic examples of coastal erosion\ud in Europe. Study of the shoreline evolution in this area between 1876 and\ud 2005 was used as the starting point of the present paper that investigates over\ud a span of seven years (2005 to 2012), by using remotely sensed data. The aim\ud is to adapt and integrate geomatics techniques to transform very high\ud resolution satellite images in powerful tools to analyse coastline changes. So,\ud in order to identify eroded and added areas, IKONOS-2 (2005), GeoEye-1\ud (2011) and WorldView-2 (2012) imageries are compared. These data-sets\ud were re-georeferred to improve the positional accuracy. More over\ud Normalized Difference Water Index (NDWI) was applied to pan-sharpened\ud multispectral images to facilitate coastline vectorising at the same\ud geometric resolution of panchromatic data. In addition, variance\ud propagation was considered to establish the accuracy of the reconstruction\ud of coastal evolution. Added and eroded areas were defined and related to\ud the impact of the defence structures that were built in this zone in 2011
Very High Resolution (VHR) satellite systems are platforms whose sensors acquire high geometric resolution images. Since 1972, when the first satellite was launched (Land sat ERTS), the spatial resolution of the satellite image has increased, making Ground Sample Distance (GSD) reaching 0.30 m at Nadir in panchromatic images. In this paper, after a brief introduction, concepts relative to orbits, types of sensors and resolutions are reported. Geostationary and sun-synchronous orbits are described; difference between push-broom and whisk-broom sensors are reported; the definition of the geometric, the radiometric and the temporal resolutions are listed. In the end, the characteristics of the most common VHR commercial optical satellite are mentioned: IKONOS-2, QuickBird-2, SPOT-5, GeoEye-1, WorldView-2 and WorlView-3 satellites.
The integration of thematic layers and DTM (Digital Terrain Model) becomes possible to achieve 3D models that can contextually display the variability of both the morphology and territorial and / or environmental components. WorldView-2 high resolution images, presenting a reduced size of the pixels on the ground (0.5 m in panchromatic and 2 m in multispectral) and a high spectral resolution (with 8 bands in the portion of the electromagnetic spectrum between wavelengths 400 nm and 1040 nm) allow the creation of very detailed maps of land cover. The simultaneous availability of DTM with appropriate cell size transforms these thematic layers in digital 3D models with high resolution.\ud This paper is aimed to test positional and thematic accuracies that can be achieved in the construction of 3D models of land cover using WorldView-2 images. Phlegraean area (in Campania region, Italy), characterized by particular morphological configuration, mainly due to the presence of craters and volcanic cones, is considered. The dataset is firstly orthorectified, using rational polynomial functions, and then processed using supervised classification (Maximum Likelihood method) to identify several homogenous classes. The indices derived by confusion matrix (Producer Accuracy, User Accuracy, Overall Accuracy, Cohen Index) permit to check the thematic accuracy. DTM is derived from technical maps (at 1:5.000 scale) and used as the basis for 3D models of land cover
Italian coasts are subjected to morphological modifications that in the last decades have, in many cases, been the cause of considerable coast-line withdrawal. A detailed cognizance on dynamics and relative consequences on territory and environment is necessary to plan actions for limiting these events and their impacts. Reconstruction of temporal shoreline changes can be realized using historical and recent maps, remote sensed images and topographic survey results.
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