OpenStreetMap (OSM) is currently the largest openly licensed collection of geospatial data, widely used in many projects as an alternative to or integrated with authoritative data. One of the main criticisms against this dataset is that, being a collaborative product created mainly by citizens without formal qualifications, its quality has not been assessed and therefore its usage can be questioned for some applications. This paper provides a map matching method to check the spatial accuracy of the building footprint layer, based on a comparison with a reference dataset. Moreover, from the map matching and a similarity check, buildings can be detected and therefore an index of completeness can also be computed. This process has been applied in Lombardy, a region in Northern Italy, covering an area of 23,900 km 2 and comprising respectively about 1 million buildings in OSM and 2.8 million buildings in the authoritative dataset. The results of the comparison show that the positional accuracy of the OSM buildings is at least compatible with the quality of the reference dataset at the scale of 1:5000 since the average deviation, with respect to the authoritative map, is below the expected tolerance of 3 m. The analysis of completeness, given in terms of the number of buildings appearing in the authoritative dataset and not present in OSM, shows an average percentage in the whole region equal to 57%. However, worth noting that the opposite, namely the number of buildings in OSM and not in the reference dataset, is not zero, but corresponds to 9%. The OSM building map can therefore be considered to be a valid base map for direct use (territorial frameworks, map navigation, urban analysis, etc.) and for derived use (background for the production of thematic maps) in all those cases where an accuracy corresponding to 1:5000 is required. Moreover it could be used for integrating the authoritative map at this scale (or smaller) where it is not complete and a rigorous quality certification in terms of metric precision is not required.

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ABSTRACT:OpenStreetMap (OSM) is currently the largest openly licensed collection of geospatial data. Being OSM increasingly exploited in a variety of applications, research has placed great attention on the assessment of its quality. This work focuses on assessing the quality of OSM buildings. While most of the studies available in literature are limited to the evaluation of OSM building completeness, this work proposes an original approach to assess the positional accuracy of OSM buildings based on comparison with a reference dataset. The comparison relies on a quasi-automated detection of homologous pairs on the two datasets. Based on the homologous pairs found, warping algorithms like e.g. affine transformations and multi-resolution splines can be applied to the OSM buildings to generate a new version having an optimal local match to the reference layer. A quality assessment of the OSM buildings of Milan Municipality (Northern Italy), having an area of about 180 km 2 , is then presented. After computing some measures of completeness, the algorithm based on homologous points is run using the building layer of the official vector cartography of Milan Municipality as the reference dataset. Approximately 100000 homologous points are found, which show a systematic translation of about 0.4 m on both the X and Y directions and a mean distance of about 0.8 m between the datasets. Besides its efficiency and high degree of automation, the algorithm generates a warped version of OSM buildings which, having by definition a closest match to the reference buildings, can be eventually integrated in the OSM database.

Background: NASA World Wind is an open source application-programming interface for developing geographic information systems based on a virtual globe rendering engine representing a planet. NASA World Wind provides the ideal environment for scientific data, their analysis, visual representation and interaction with users, in a single platform, which can be deployed both as a Java desktop application (NASA World Wind) or a JavaScript web application (ESA-NASA Web World Wind).

ABSTRACT:Cartographic cultural heritage preserved in worldwide archives is often stored in the original paper version only, thus restricting both the chances of utilization and the range of possible users. The Web C.A.R.T.E. system addressed this issue with regard to the precious cadastral maps preserved at the State Archive of Como. Aim of the project was to improve the visibility and accessibility of this heritage using the latest free and open source tools for processing, cataloguing and web publishing the maps. The resulting architecture should therefore assist the State Archive of Como in managing its cartographic contents. After a pre-processing consisting of digitization and georeferencing steps, maps were provided with metadata, compiled according to the current Italian standards and managed through an ad hoc version of the GeoNetwork Opensource geocatalog software. A dedicated MapFish-based webGIS client, with an optimized version also for mobile platforms, was built for maps publication and 2D navigation. A module for 3D visualization of cadastral maps was finally developed using the NASA World Wind Virtual Globe. Thanks to a temporal slidebar, time was also included in the system producing a 4D Graphical User Interface. The overall architecture was totally built with free and open source software and allows a direct and intuitive consultation of historical maps. Besides the notable advantage of keeping original paper maps intact, the system greatly simplifies the work of the State Archive of Como common users and together widens the same range of users thanks to the modernization of map consultation tools.

ABSTRACT:Inspired by the visionary idea of Digital Earth, as well as from the tremendous improvements in geo-technologies, use of virtual globes has been changing the way people approach to geographic information on the Web. Unlike the traditional 2D-visualization typical of Geographic Information Systems (GIS), virtual globes offer multi-dimensional, fully-realistic content visualization which allows for a much richer user experience. This research investigates the potential for using virtual globes to foster tourism and enhance cultural heritage. The paper first outlines the state of the art for existing virtual globes, pointing out some possible categorizations according to license type, platform-dependence, application type, default layers, functionalities and freedom of customization. Based on this analysis, the NASA World Wind virtual globe is the preferred tool for promoting tourism and cultural heritage. This is because its open source nature allows unlimited customization (in terms of both data and functionalities), and its Java core supports platform-independence. Relevant tourism-oriented World Wind-based applications, dealing with both the Web promotion of historical cartography and the setup of a participatory Web platform exploiting crowd-sourced data, are described. Finally, the paper presents a project focusing on the promotion of the Via Regina area (crossing the border between Italy and Switzerland) through an ad hoc World Wind customization. World Wind can thus be considered an ideal virtual globe for tourism applications, as it can be shaped to increase awareness of cultural history and, in turn, enhance touristic experience.

Virtual globes were initially released as effective and intuitive tools to view satellite and aerial photos directly superimposed on the 3D modeling of the globe. The constant update of increasingly accurate and detailed images and the ability to customize the content through the direct mapping on the globe of any geographically localized phenomenon (physical, environmental, social, etc.) have increased not only the common and popular use of virtual globes but has also offered great opportunities for geographical representation and analysis in science. The paper presents solutions we implemented for environmental purposes; in particular, three different viewers for 4D environmental variables (3D location of the variable at different times) using an open-source virtual globe developed by NASA (NASA World Wind). The third solution presented is the most innovative one and uses a “doxel-based” approach for modeling environmental variable distributions. The choice of World Wind is due to its code openness and hence the possibility for both customizing and extending its functionality. The characteristic of being written in Java makes it a platform-independent program (viewer directly executable on different operation systems) and accessible by simple web-browsers (like applet or via Java Web Start technology). In detail, we present solutions that can be directly implemented using existing software tools and an innovative solution specifically developed

Driven by the rise of Web 2.0 and the non-stop spread of mobile device sensors, the concept of Public Participation GIS (PPGIS) is knowing a revolutionary era which perfectly fits the new vision of Digital Earth (DE). This research investigates the opportunity to build up a PPGIS prototype with completely Free and Open Source Software (FOSS) architecture, in which data directly come from field surveys carried out by users. A sample application related to urban monitoring is addressed, which concentrates on user field-collected data concerning reports of road pavement damages. Open Data Kit suite allows users to collect geotagged multimedia information using mobile devices with onboard location sensors (e.g. a Global Positioning System receiver). On field-captured data are sent to a server and stored into a PostgreSQL database with PostGIS spatial extension. GeoServer then disseminates data on the Web. On the client-side, different solutions allow data visualization on both desktop computers and mobile devices. The designed architecture provided support for FOSS usage in the process of gathering, uploading, and Web publishing information collected in situ. The implementation of the developed PPGIS could thus substantially increase public active participation in data creation and sharing, besides enlarging DE knowledge up to the local level