1,721,046 research outputs found
Comparazione tra alcuni metodi di Pan-sharpening applicati ad immagini GeoEye-1
No full textA bordo del satellite GeoEye-1 sono presenti sensori
operativi nel pancromatico e nel multispettrale: la risoluzione
geometrica delle immagini acquisite risulta essere più elevata nel
primo caso (50 cm) piuttosto che nel secondo (2 m). I metodi di
Pan-sharpening consentono di migliorare le dimensioni originali
dei pixel delle immagini multispettrali riportandole a quelle delle
immagini pancromatiche. In tal modo diviene possibile ottenere
dati di elevato dettaglio, sia geometrico che spettrale, anche da
satellite, raggiungendo performance sinora garantite solo da foto
da aereo. In questo lavoro si confrontano i risultati ottenuti, per
una scena GeoEye-1 relativa ad un’area della Provincia di
Caserta, dalle applicazioni di 6 differenti metodi di
pansharpening individuati tra i più ricorrenti o comunque
efficaci presenti nei software di elaborazione delle immagini
telerilevate. In particolare si considerano: metodo IHS (Intensity-
Hue-Saturation), trasformazione di Brovey, metodo
moltiplicativo, metodo della media semplice, metodo della
Sostituzione delle Componenti Principali, metodo di Zhang. I
risultati vengono analizzati e comparati mediante l’utilizzo di due
indici di qualità: coefficiente di correlazione e ERGAS
TOA reflectance and NDVI calculation for Landsat 7 ETM+ images of Sicily
No full textNDVI (Normalized Difference Vegetation Index) is useful measure of live green vegetation obtained with remotely sensed data. For its calculation two images concerning reflectance of the scene in red and infrared bands are necessary. Results can be classified to obtain land cover map distinguishing three classes: waters (oceans, seas, lakes, rivers, ...), soils (rocks, buildings, roads, ...) vegetation (forests, grasses, orchards, ...). Landsat 7 ETM+ images (band 3 and band 4) can be used for NDVI calculation, but if data have been formatted to fit in 8-bit numbers (ranges from 0-255), transformation is necessary to obtain reflectance values. One of the solution is to consider “top of atmosphere” (TOA) measurements: solar radiation incident on the satellite sensor is derived by digital numbers. The aim of this paper is to demonstrate the advantages of this transformation, even if it doesn’t supply the effective reflectance at soil: Landsat ETM+ red and near-infrared images of Sicily were considered and NDVI was calculated in two different ways, with and without TOA transformation of original data. Results were compared to remarks better performance of the first approach
BATHYMETRY FROM WORLDVIEW-3 SATELLITE DATA USING RADIOMETRIC BAND RATIO
Full text linkThe use of optical satellite sensors allows to obtain bathymetry data on large area ina short time and in a cheap way. In addition, in particular places where it is difficult to carry out the survey by classic methods, the bathymetry from satellite data can be the only mode to obtain the depth of the backdrop. So, the aim of this research paper is to analyse the potential of the eight bands and the very high resolution of the commercial satellite WorldView-3 (WV-3) in order to obtain bathymetric data. Using WV-3 satellite data and the Stumpf method, the paper intends to investigate the possibility of obtaining bathymetric data in a specific area where the water is not particularly clear. To achieve this goal, in Geographic Information System (GIS) environment, several algorithms have been developed. The comparison between the results and the reference bathymetric data shows a huge potential of the WV-3 satellite data. The area of study concerns the port area of the city of Lisbon and a part of the river Rio Tejo, in Portugal
Sistemi Informativi di ausilio alla navigazione basati sull’impiego di cartografia numerica
No full textA New Index to Perform Shadow Detection in GeoEye-1 Images
No full textWith the introduction of new satellites for earth monitoring characterized by very high
resolution (VHR) sensors, new algorithms to recognize shadow in the supplied images are necessary.
Automatic shadow detection can enhance the interpretability of the images in several applications such as
classification and change detection. Several approaches are present in literature for shadow detection and
their adaptation and particularization for VHR satellite images are still in evolution. The goal of this
paper is to propose a new index for shadow detection based on multispectral files processing. GeoEye-1
satellite data are used for this study: IHS pan-sharpening method is applied to transfer pixel dimensions
of the panchromatic image (spatial resolution: 0.5 m x 0.5 m) into the multispectral images (2 m x 2 m);
an index named ERGAS is used to test the quality of the resulting raster files. Dealing with the problem
of the shadow detection, a new index is defined to identify the affected pixels both in the original as well
as pan-sharpened images. The results are compared with them by another index named ratio that is
generally applied for shadow detection in multispectral images: issues and advantages, derived by using
the proposed technique, are discussed
Increasing Geometric Resolution of Data Supplied by Quickbird Multispectral Sensors
No full textOn board of Quickbird satellite two types of sensors are present: panchromatic and multispectral. The
first acquires earth images within spectral range 0.405 μm – 1.053 μm; the second acquires simultaneously four
images of the same scene, each of them within shorter range of spectrum (Blue, Green, Red, Near-Infrared).
Panchromatic images present geometric resolution 0.60 m while multispectral ones 2.40 m. For many
applications, detailed data are welcome, so in the last decades several methods have been elaborated in Remote
Sensing to transfer pixel dimensions of pan images into multispectral images. Included in data fusion
techniques, they are named pan-sharpening methods and one of the principal problems they are called to resolve
is to define weights to attribute to each multispectral component in fusion operations. The aim of this paper is to
consider the application to Quickbird imagery of two efficient pan-sharpening methods, IHS and Brovey
transformation, demonstrating that multispectral weights can be easily derived by analysis of sensors relative
spectral radiance response
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