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National map distribution service using image web server in Italy

As a part of the development of the Italian Cartographic Reference System, the Italian Ministry of the Environment has developed, in collaboration with Planetek Italia, a public web site (www.atlanteitaliano.it), allowing unrestricted Internet access to various types of maps and photographic images covering the whole of Italy.

The types of data available on-line include black and white and colour orthophotos at 1 meter resolution (nominal scale 1: 10.000); maps of the Italian Geographic Military institute (IGM, scale 1: 25.000, 1: 100.000, 1: 250,000 1: 1.000.000); and a digital elevation model (DEM). The data, compressed in ECW format, are distributed using Image Web Server with the specific advantage that the imagery may be accessed via the Internet in real time in two ways; either through the website using a common browser or directly inside any common supported desktop GIS application using the individual image URL (only registered and entitled users are permitted access to the URL’s).

By going to the website users are given three different ways to view the cartography: single view, double view and transparency.

-Single View : this kind of visualization is the most immediate and produces a single large view of the image on the screen together with the complete technical information about the images showed.

-Double View : this kind of visualization places two geo-linked images side by side. The images can be of the same area but could, for example, be taken at different times, thus allowing for change detection to be carried out.

-Transparency : this kind of visualization allows the overlaying of two different images with full, on-the-fly, transparency and layer position control. Viewing images in this fashion permits different kinds of visualization, for example, multi-temporal analysis can be carried out between data acquired in different years, for the monitoring of environmental change. The images need not be the same type, thus you can overlay and compare recent orthophotos with older cartographic data.