Using Worldview-2 Satellite Imagery to Support Geoscience Studies on Phlegraean Area

Abstract

WorldView-2 satellite imagery includes half-meter panchromatic resolution and 2 m multispectral resolution. Because of the reduced dimensions of pixels and articulated spectral acquisition these images supply detailed information that can be used for geoscience applications, above all to investigate areas, identify land cover, bound vegetated zones, outline transformations (change detection). The aim of this study is to remark possibilities to use WorldView-2 imagery for analysis of Phlegrean area (Italy), facilitating monitoring actions and increasing level of knowledge of territorial and environmental features. This area is emblematic for many aspects such as its geological history, the presence of volcanic activities, the Roman ruins and the natural forest. The study is centered on methodological aspects about the use of WorldView-2 imagery for increasing dataset and level of information. For consequence attention is firstly focalized on possibilities to obtain geometrical corrected data with adequate accuracy (comparable to pixel dimensions): using Rational Polynomial Functions for ortho-rectification, references are already georeferred air-photos with cell-size equal to that of WorldView-2 higher resolution images (panchromatic band: 0.50×0.50 m), while Digital Terrain Model (DTM) is built with cartographic dataset in scale 1: 5,000. Then other two methodological aspects on WorlView-2 imagery use are considered: Normalized Difference Vegetation Index (NDVI) application and 3d photo-realistic model construction. In the first case thresholds determination to distinguish vegetated areas is conducted using Maximum Likelihood method based on training sites to achieve high level of thematic accuracy; in the second RGB composition is obtained and overlapped to DTM.