1,720,967 research outputs found
Multi-frame and multi-dimensional historical digital cities: the Como example
No full textIn this article, we present the realisation of a multi-frame and multi-dimensional WebGIS that allows users to simultaneously analyse a specific portion of the Earth taking into account the historical information, too. Two graphical panels have been realised: one for the usual 2D view and one for a more realistic 3D view. Both panels display historical maps of the city, the current orthophoto and the digital topographical map. The 3D frame is based on NASA World Wind, an open source virtual globe from where 3D buildings are shown extruding the 2D shapes using their mean height. Thanks to a specifically designed graphical user interface, it is also possible to dynamically thematise the buildings on the globe according to different criteria (e.g. the construction time span) so that only the geometries fulfilling the request are turned on. Within the proposed application, a synchronisation between the two panels has been implemented, in order to maintain a constant alignment of the two viewers. The application is also open to the time dimension. In fact, assigning to each geometry two dates (e.g. ‘year of construction’ and ‘year of demolition’), it is possible to dynamically view how buildings have changed over time, both in their shape and height. Future developments of this work will concern the possibility of implementing a city model with a higher level of detail
Densificazione di DSM LiDAR per la creazione di true-ortofoto: primirisultati con un metodo robusto di modellizzazione 3D degli edifici
No full text
Uso del software goGPS per la produzione della sentieristica di un parco con strumenti a basso costo
No full textApplied free and open source software web mapping clients in education and application sides
No full textLiDAR digital building models for true orthophoto generation
Full text linkThe importance of digital orthophotos in spatial
databases has increased in recent years, since they are an
efficient, low-cost and, if properly managed, accurate
product. Usually, the generation of orthophotos is carried
out using digital terrain models (DTMs); meaning without
taking into account vegetation, buildings, and other
attached and detached structures. This leads to low
accuracies in urban areas, bringing distortions into the
image. To avoid this unwanted effect, one must adopt a
digital surface model (DSM), as proposed by Amhar et al.
(Int Arch Photogrammetry Remote Sens 32(4):16–22,
1998). The method proposed in this paper allows for the
creation of true orthophotos by using a DSM to refine the
representation of buildings. The pixel size of the DSM must
be similar to that of the true orthophoto in order to model
the roof edges with sufficient accuracy. This paper presents
a new method capable of correcting the roof displacement
using an approach based on the integration of several
products today available in public administrations, such as
a geodatabase, DTMs/DSMs, and light detection and
ranging (LiDAR) data. The method is based on a rigorous
modelling of simple roofs starting from their 2D projection
in the geodatabase, while information about their heights
can be obtained using LiDAR data. For some selected
simple roofs, automatic modelling can be carried out, in
which a robust interpolation method, such as RANSAC, is
used to model the pitches identified by a clustering
procedure. For complex roofs, where creating a rigorous
model in a fully automatic way is not possible, a procedure
based on the thickening of a DSM is carried out
Web Services and Historical Cadastral Maps: the first Step in the Implementation of the Web C.A.R.T.E. System
Full text linkIn the State Archive of Como, Northern Italy, about 15000 historical cadastral maps corresponding to 246 current municipalities of Como and Lecco districts are preserved. These maps belong to different cadastral
productions: the Theresian cadastre, promoted in 1718 by Emperor Carl VI and come into force in 1760 during the reign of Maria Teresa; the Lombardo-
Veneto cadastre, started in 1854 and completed, with continuous updates during the time, at the end of the century; and finally some maps of 1905 belonging to the New Lands Cadastre, the first national geometric cadastre after Italian unification of 1861. Maps have not only a considerable artistic value but mostly a cultural and historical one, since they constitute a great source to derive an accurate representation of the territory and its evolutions. For these reasons, the old maps represent nowadays a valuable instrument for historians, scholars and professionals working both in the historical research field and in the urban and territorial planning. The project Web C.A.R.T.E. (Web Catalogo e Archivio delle Rappresentazioni del Territorio e delle sue Evoluzioni), sponsored by the Fondazione Provinciale della Comunità Comasca Onlus, has been started to enhance the immense
cartographic heritage of the State Archive of Como using the most recent technologies of map processing and web services.
After the maps digitization step, performed by the State Archive in agreement with the interested municipalities, a georeferencing and warping procedure is needed to place the cadastral maps in the actual Italian reference system, thus making it possible to overlap them to the current cartography. Being the most of the maps divided in sheets, that have been surveyed and drawn independently from each other, the preliminary step has been to combine the sheets in a single map by applying to them a roto-
translation with a scale variation. The georeferencing of unified maps has then been performed and tested in different software and GIS packages to determine the optimal solution. Finally PCI Geomatica OrthoEngine has been chosen, thanks to its variety of implemented mathematical models and to the possibility of inserting not only Ground Control Points (points of known coordinates, both in the actual cartography and in the historical map, that are used to compute the mathematical model) but also Check Points, points with known coordinates that are not included in the transformation and can therefore be used to check the model accuracy. The residuals of the transformation have then been used to determine the best georeferencing model for each cadastral map, confirming the choice with statistical techniques.
The following step has been the documentation of georeference d maps in terms of metadata, a series of information needed to precisely identify the data and get information about their content, accuracy, accessibility and usage constrains. Metadata schema are currently defined by national and international standards: at the Italian level, the CNIPA (Centro Nazionale per l’Informatica nella Pubblica Amministrazione) proposed in 2006 a standard which is in agreement with the European Directive INSPIRE and defines a common set of metadata related to all kinds of geographic information used by national Public Administrations. Metadata for the historical georeferenced maps have therefore been compiled according to the Italian standard; last step has been their publication on the Internet through GeoNetwork, an open source web geo-catalogue that allows users to immediately identify a data and derive (from its metadata) information about language, spatial extent, reference system, responsible person or agency, accessibility, possible limitations on the usage, data origin and production process, and other features.
Digitized and georeferenced maps, accompanied by their metadata, can finally be visualized and navigated online through the implementation of a dedicated webGIS. The realization of this viewing service implies the usage of software and tools both from the server and the client-side. Applying FOSS (Free and Open Source Software) solutions, a system with interactive functionalities and able to manage large raster maps has been developed. The entire service is currently in a test phase to verify its fulfilment of specific requests and needs expressed by experts from the State Archive; for this reason it may be possible that new and improved solutions will be introduced in the future
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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