We emphasize the importance of GIS for establishing link between spatial features and the database of data for constructing a query during the local and network analysis. This link, used to identify those records in the database that meet certain conditions, is possible only with a GIS tool. The majority of scientists that work in the field of preservation of works of art use various software to perform the task of representing the building spatially and analyzing the measured variables, but these packages do not allow database manipulation.

SURFER, for example, interpolates scattered data very well, it is also able to export them in .shp format, ready to be displayed on the Internet, but it is not able to produce the other files needed to process information through database query, or advanced math analysis functions.

For these reasons the collected data have been analyzed using a GIS package (ESRI-ArcView), but others (Er Mapper, IDRISI for example) could be employed to obtain the output necessary to display maps on the WEB.

Additional ESRI-tools have been required, such as:

• Cad Reader to work with CAD drawing themes, for example the map of the church in .dxf o .dwg format;
• Spatial Analyst tool, as the problem requires continuous surface (raster) modeling information, i.e. to create continuous surfaces from scattered point features;
• Other freeware scripts (available on http://arcscripts.esri.com/) have been useful for our aim; they are :
• KGDI, that allows the generation of contour or surface using the Kriging data interpolating method;
• EDTOOLS, to convert DXF file into polygons, to generate an analysis that requires combined information represented both as raster data and vector data (boundaries). This extension is necessary when there is the need to remove grid node data from a grid in areas not supported by original data or in areas where one does not want to display contours on a map (analog of a "blanking file" in SURFER).

On the WEB it can be founded many manuals to help one to analyze and produce shapefiles that will be managed by Mapserver and then displayed by a browser (Netscape or Internet Explorer can be used, no particular plug-in are required!). The logic of the process to obtain files for the network is demonstrated in the flowchart below.

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Figure n.1 shows a typical map obtained [7]

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The programs were developed as Common Gateway Interface .pl) executables to be run on a Apache or Windows NT/2000 Web Server. All the applications were written in PERL [8] that dynamically interacts with MapServer, allowing easy navigation across the tables.

Analyses based on the Boolean logical operators can be made. Data selection and query can be performed by inserting parameters that will be processed by a Perl script. The obtained results are presented clearly and efficiently using maps and chart as those shown in (fig. n.2):

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It is possible to upload data and make them immediately manageable
by everyone that can connect the URL; filename can be modified
and/or deleted. To access to these options an authorized login is
required

A typical window for this task is shown in (fig. n.3):

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ASCII tables and shapefiles (.shp, .shx, .dbf, .sbx, .sbn) can be downloaded in compressed format and can be managed using a GIS tool. Graphic outputs (maps) are in GIF or Portable Network Graphics (PNG) format [9], which is a patent-free replacement for GIFs.