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Geoinformatics_01-2009
article building geo-knowledge scanning and imaging in the city of bergamo laser and image geo-technologies can record in a digital way the spatial reality of a building, with its shape and dimensions, colours of materials and decay (geo-knowledge). the different cultural aspects of these topics are examined here in detail and pointed out with the support of a test case regarding a historic building in the city of bergamo (italy). by luigi colombo and barbara marana fig. 1 - wireframe representation of an ancient building pictures and survey an ancient chinese saying asserts that a picture is better than a thousand words and pictures, in the form of a drawing before, and an image afterwards, have become the main tool to create an effective syntheses for metric and thematic interpretations of reality (geo-knowledge). in fact, it is possible to document and render built environments, according to their shape, size, colors and condition of decay. typically, spatial features of buildings have been geo-coded through different representation techniques: first of all drawing , a meta-language which allows you to read the spatiality of an object and communicate its evolutionary dynamics; then, imaging which can definitively record, by means of electronic sensors, quantitative and semantic information documenting geometry with its changes and object details, even the smallest ones. finally, spatial model which offers a reconstruction of planned or real spaces, with or without surface photo mapping, allowing a more complete reading of the formal, structural and functional values of the building. thank to the informatics revolution and process automation, current measurement technology provides more automated and coded models for geo-knowledge this has caused the replacement of typical subjectivity of the final document with a new objectivity, both in recording and drawing entities. in general, it could be said, by paraphrasing the pictorial themes proper of picasso s reality decomposition, that modern geo-technologies record a model of existing scenes through the cartesian research of their shape . spatial techniques nowadays, the graphic representation of virtual reality models is much more oriented towards 3d visualizations, with a wide description of textures and colors, such as in matisse s painting. a spatial reading, at different levels of knowledge, is required for sensible structures and is the basis for the construction of building information systems. the spatial representation approach starts from the methods of solid constructive geometry in which a 3d model is created by combining elementary primitives (such as cubes, spheres, cones, cylinders or pre-defined objects) according to well-known boolean operations (addition, subtraction, intersection, etc.). however, if surfaces of interest show irregular shapes, a collection of 3d points, applying non-contact passive or active techniques, is requested: these methods can be classified as image and range based modeling. spatial visualization is performed in a wireframe way (feature hedges only) (fig. 1), as flatshading models, with low-level texturing, or through photo-rendering of point or surface models; the last approach is a solution of great jan./feb. 2009 fig. 2 - spatial modelling and geo-techniques 24
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