1,721,021 research outputs found
Sistemi Informativi di ausilio alla navigazione basati sull’impiego di cartografia numerica
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Synthetic Sensor of Landsat 7 ETM+ Imagery to Compare and Evaluate Pan-sharpening Methods
No full textSeveral studies and applications are present in literature to compare pan-sharpening methods: the
greater part of them is based on indexes that relate radiometric characteristics of derived images to the
correspondent original ones. Among others correlation index, RMSE (Root Mean Square Error), UIQI
(Universal Image Quality Index) and RASE (Relative Average Spectral Error) are used, but evaluation is limited
if there aren’t other multispectral images with higher geometric resolution to which compare the pan-sharpened
results. In this paper Landsat 7 ETM+ artificial sensor was introduced to permit more reliable comparison and
evaluation of pan-sharpening methods. Data concerning Campania region (Italy) were used: firstly Landsat 7
ETM+ panchromatic image and multispectral ones with acquisition bands within that of pan were processed to
conduct their digital numbers to radiance values; then synthetic sensor was considered and geometric resolutions
degraded by reducing original pixel dimensions 15 m × 15 m and 30 m × 30 m respectively to 30 m × 30 m and
60 m × 60 m. In other terms, new images were derived as equivalent products to those that should have been
obtained by sensor with lower geometric resolutions but same acquisition bands of Landsat 7 ETM+
(panchromatic and multispectral). Pan-sharpening methods were applied to derived images and products
compared with original data so to obtain a credible evaluation of performances of the implemented approaches
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
Ricevitori GPS a basso costo per uno studio del wake wash
No full textIl trasporto con High Speed Craft (HSC), ossia con aliscafi, catamarani e monocarena, comporta indiscutibili vantaggi negli spostamenti via mare; per contro, le elevate velocità raggiunte da tali mezzi provocano onde di wake wash che hanno impatto negativo sull’ambiente costiero e sulle strutture poste in prossimità del bagnasciuga, nonché sulla sicurezza delle persone. Tali onde possono essere notevolmente ridotte stimandone l’entità e scegliendo opportunamente rotte e velocità.
In questa nota si descrive uno studio effettuato a tal fine in cui si evidenzia come, con l’ausilio di cartografia e di ricevitori satellitari GPS a basso costo, sia stato possibile determinare, con precisioni idonee alle finalità richieste, un insieme di parametri (distanza dalla costa, velocità e profondità), relativi ad un HSC, da correlare ai dati ondametrici per l’analisi del fenomeno.The transport with High Speed Craft (HSC), in other words with hydrofoils, catamarans and monohulls, involves indisputable advantages in the movements via sea; on the other hand, the high speeds reached by these means cause wake wash waves that have negative impact on the coastal environment and on the structures set in proximity of the shoreline, as well as on people safety. These wake wash waves may be significantly reduced by estimating their magnitude and choosing opportunely routes andspeed.This note describes a study conducted for this purpose which shows how, with the aidof cartography and low-cost GPS satellite receivers, it is possible to detect, with accu-racy suitable to the purposes required, a set of parameters (distance from the coast,speed and depth), relative to an HSC, to be correlated with wavemeters data for the phenomenon analysis
Applicazione di Tecniche di Pan-Sharpening IHS ad immagini IKONOS
No full textSatellite multi-spectral images present, compared with panchromatic ones, better spectral resolution (from 0.01 μm to 0.1 μm rather than 0.3 μm or over), but greater pixel dimensions. True colour composition RGB, derived from red, green and blu wavelength bands, has geometric resolution of multi-spectral images which turns out to be therefore smaller of that of the panchromatic one. Pan-Sharpening techniques concur to go beyond this limit and obtain coloured images that have the same pixel dimensions which characterize panchromatic data.
In this paper Pan-Sharpening techniques based on HIS (Intensity, Hue, Saturation) model are considered in relation to their application to IKONOS images. Attention is focalized on the principal problem which is generated by the contribution of neared infrared to panchromatic images, and solution proposed in literature are adopted. Applications are conducted on IKONOS images concerning Ustica Isle (Sicily) and results are analyzed
Rappresentazione dei rischi georiferibili mediante tecniche di cartografia numerica in ambiente GIS
No full textLa cartografia in rete e nelle applicazioni WEBGIS
No full textThe term WEBGIS (alternatively WEB-based GIS, Online GIS, Distributed GIS) is used to indicate via Internet/Intranet use of Geographic Information Systems functions, so to supply georeferred information to users. As well as in no-web applications, element of fundamental importance is cartography, or, in other terms, the representation of hearth surface (or part of it), to which databases are linked. Presence of cartographic files in web does not imply WEBGIS: sometimes there are only static pages to which user accesses without activation of spatial analysis.
In this paper, considering bibliographic research and experiments conducted at Geomatic Laboratory of Faculty of Sciences and Technologies of University of Naples “Parthenope”, an overview on state of art concerning maps in WEB and in WEBGIS is supplied. Particularly, criteria for distinction and classification of possibilities to insert and use geographic data in Internet and to manipulate them are evidenced. Principal characteristics of languages, formats and standards to insert in Internet maps are considered, such as HTML (HyperText Markup Language) and SVG (Scalable Vector Graphics); particular attention is reserved to GML (Generalized Markup Language) from OGC (Open Geospatial Consortium), which can include in each feature both spatial information as well as attributes (generally included in linked alphanumeric databases)
Trasformazioni di datum e di coordinate in alcuni software gis: applicazioni concernenti il territorio della Campania
No full textIn this paper results obtained with automatic executions of datum and coordinates transformations using some GIS softwares are described: 43 points of IGM95 network within Campania Region, which are known in reference to UTM-WGS84 and Gauss-Boaga Roma40, have been considered; two vector files, one in UTM-WGS84 plane coordinates, the other in UTM-WGS84 geographic coordinates, have been produced.
Using softwares ArcGIS 8.3 (ESRI, 2002), Autodesk Map 3D 2005 (Autodesk, 2005), Idrisi 32 Release 2 (Clark Labs, 2002) and MapInfo Professional 7.0 (MapInfo Corporation, 2002), datum transformations (from WGS84 to Gauss-Boaga Roma 40) and coordinates transformations (from UTM-WGS84 plane coordinates to UTM-WGS84 geographic ones) have been applied; the results have been compared with values supplied by IGM. To conduct additional analyses, for 43 considered vertices also UTM-ED50 coordinates have been calculated with Verto1 (IGM, 2002) and used as comparison terms for analogous ones derived from applications of above mentioned GIS softwares.
Datum transformations concerning plane coordinates have been applied using similitude (4 parameters: 1 rotation, 2 translations, 1 factor scale) in CAD MicrostastionV8 XM Edition (Bentley, 2005); in this case 4 points known in the different systems have been considered
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