Technical Report on Point Cloud - Essay Example

POINT CLOUD (technical report AND reflective report) There is a high need of having semantically and structured enriched 3D of the historical building 3D digital models so as to handle, conserve, restore, and modify the projects. To acquire correct data in the building, and corridor, different techniques of survey would be adopted like the laser scanner that allows the obtained raw data to point in the buildings of the cloud. It is also necessary to have a focus on the efficient ways of shifting from the raw 3D data to a semantic and complete enriched CAD model of the building. The building information concept, the democratization and its expansion of the professionals in the AED field, and making it basic in the semantization quest of the digital mock-ups. In this case, it can be defined as both the methodology and the technology. It is a technology since it involves some digital representation of the functional and physical characteristics of the building. It can be considered being a methodology since it helps in the collaboration of different actors in various phases of the building life cycle. It is established on a number of architectural building information concerning components, building information, relations and characteristics between them while allowing all of them to enrich and complete the purely description of the digital mock-up through the association of the features that are semantic. The basic problem in architecture involves the fact that there is no efficient software that ensured the direct shift from the cloud points to the completely enriched CAD models, despite the fact that some software companies do propose new tools used in the exportation of the point of clouds. In essence, dedicated software has the ability of helping the semantically structured or efficiently segmented cloud points of the historic buildings. The specificity of the historical component makes the task extremely difficult in order to construct an efficient digital representation of the historical buildings and is basic in analysing and understanding the whole chain moves from the one 3D point cloud acquired to semantically and well-structured enriched models. This process considers three key steps including the acquisition of data, enrichment of the 3D model, and segmentation of data. It is vital to highlight the BIM approach that starts to be largely used in the architecture field of design applied techniques to the available buildings, a concept referred to as the build BIM. The BIM process is made up of converting the geometry measurements and the appearance of the available buildings semantic rich representation. This process creation is depended on the initial phase of data and survey collection, and a second phase of treatment of data resulting to the last survey phase and collection of data. A second phase of treatment of data will lead to the last semantically enriched model. The previous studies have made the proposal that a number of approaches produce BIM using different techniques, while trying to make its generation automated. The Approaches used in the collection of data. The techniques of acquiring data include photogrammetry, topometry, or laser grammetry. Topometry includes the traditional methods of doing surveys like using the optical telescopic sight, and taking the measuring system for the angular sight direction. The involved techniques result into high precision, which requires the system for the angular sight direction. The techniques would result with high precision that will require the vital quantities of work so as to find the significant structures of facilitating the post treatment. The technique will be considered being time consuming becoming more tedious whenever the objects appear complex In addition, photogrammetric is a method that uses the taken images from different points of view so as to build a 3D restitution of building and the scene. This technique adventure results from the point cloud that is enriched with the information on colour. This information would be helpful in reporting the conservation state and the historical buildings. The benefit of this technique is the point cloud that involves the enriched color information. This could be useful in informing regarding the sonservation state, in the case of historical buildings. The technique happens to be less expensive if compared with the lasergrammetry. Lasergrammetry is one easiest and speediest method. It involves a direct and relatime solution acquisition through the projection of the laser beam on the measured surface. There are different types of scanner. The long range scanners, include the involved distances through comparing the shift of the phase of the received and transmitted wave of modulated signal. Some of the triangulation scanners are calculated and a base of the effect of the beam laser using two CCD camera. Currently, the technologies of laser scanning happen to be in constant evolution allowing an appropriate clouds point and calculating the point of impact for the laser beam by one or two CCD camera. The current technologies of laser scanning happen to be in constant evolution because they allow and obtain a better clouds point quality having the highest points of density and a minimum margin of error. In addition, some hybrid approaches could be organised to form a second phase while allowing the completed missing sections of the point cloud. The effect of the technique includes the unstructured cloud point. If some hybrid approaches allow the completing of the missing sections through combining the different techniques of survey, there will be no current manner of allowing the structuring of the cloud in the acquisition stage (Arayici and Tah, 2008). Point cloud segmentation. To obtain a structures cloud point, a method of segmentation will be applied. This method could be manual, automated or rather semi automated. Some studies have note the constant progress that only lists some methods applied in an architectural field so as to facilitate the next shape recognition step. The method used in the architectural fuel is depended on the similarity of colour, together with some spatial proximity. An algorithm based on region growth is used in the neighbouring seed point of establishing the places that are refined on the colorimeter bases and the spatial relations (Arayici and Tah, 2008). The other method is depended on the detection of shape. In the first step, the algorithm will be based on growing sections and the normal adopted segment for each region planner. As built” BIM APPROACHES. BIMs concept is the latest paradigm used in the design and the management of buildings. It is in digital form and represents both the functional and physical features of buildings. In order to obtain a model that is semantically enriched, the representation should be efficient. It is widely used to design and manage new buildings. However, some researchers have tried to prove the possibility of it being applied in the cultural heritage field (Arayici and Tah, 2008). “ As-Built” BIM refers to a buildings’ BIM representation during the survey. This assists in providing information about the conservation state of historical buildings. Normally, it is a manual concept that is divided into three aspects. There is the component of geometrical modelling, the process of relating groups and material features to the components and finally the determination of associations between them.4.1 “As-built” BIM characterizations. “As-built” BIM characterization entails the definition of component shapes, attributes and relations. 4.1.1 Representation of components’ shape. A components’ shape can be grouped into three dimensions (Tang et al., 2010). It can either be local or global, parametric or non parametric and lastly implicit or explicit. Local vs. global representation In the case of a local representation, the object is partially defined while in the other hand global representation the whole object is defined. A good example of local representation is the parametric representation. Since complex shapes can be broken down into parts they are also considered to be under local representation. Non-parametric representation due to their flexibility and ability to represent an objects a whole are considered global. Parametric vs. non-parametric representation Para metric representation uses a set of parameters such as the height or width to define a model (Campbell et al., 2001). Non-parametric representation on the other hand uses different methods of characterization, for example triangular meshes. The difference between this two representations can be clearly illustrated using a cylinder. The parametric representation will describe the cylinder using its axis and radius while the non-parametric one will use a triangular mesh. Implicit vs. explicit representation Segmentation is used in cases where structured point clouds are required. This method could be automated, semi-automated or manual. In this text we will focus on some methods that have so far been used in the field of architecture so as to enable futuristic shape recognition. “As-built” BIM approaches will therefore be the main focus of this article. In the architectural field, one of the methods used is based on spatial proximities and colour similarity. This method applies an algorithm that comes up with the closest neighbour of every sea point. Regions created from this process are then joined and refined basing on spatial and colorimetrical relations. The second method is that of shape detection (Arayici and Tah, 2008). This method begins with algorithm that bases normal vectors and region growing so as divide every planar region. Analyzing the planar regions enables the extraction of architectural components. The third method uses the distance recorded between planar faces. Pottmans’ approach in 2.5D segmentation is the main inspiration to this method. The distance is recorded so as to find out the seed clusters for an algorithm growing region. Then the next step involves analyzing the components to determine their connections and merge seed-clusters that are alike. Earlier point cloud segmentation had its own demerit since it was based on surfaces segmentation. The industrial field researches mostly aimed at this issue and came up with interesting outcomes (Arayici and Tah, 2008) References Arayici Y., and Tah J., 2008. Towards Building Information Modelling for Existing Structures. Structural Survey, Vol. 26 Iss: 3, pp.210 - 222. Read More

 

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