Computer-supported Building Surveying - The Basis for Planning in Existing Built Contexts.

In view of declining populations and adequate housing provision in the western world, building in existing built contexts is becoming increasingly relevant. The conservation and use of existing buildings stock is not only ecologically sound but also an economic imperative. A prerequisite for computer-aided planning for existing buildings is both the use of on-site computer-aided surveying and the integration of all participants and disciplines in the planning process using integrated information and communication systems. The aim of this research project is twofold: to design a practice-relevant software concept for the support of the entire building surveying process embedded in the planning process, and to develop a practice-oriented mobile, digitally supported equipment and system environment for the digital architectural surveying of buildings. This paper will discuss the IT concept of a building surveying system, the software and hardware prototypes developed as well as usability aspects of wearable computers. Motivation – the current situation in Europe In the next few centuries, most building uses will involve already existing buildings. The planning tasks of the future will involve the skillful re-use and adaptation of what already exists, whether they be private dwellings which are converted or extended, the extension of public buildings or the reclaiming of entire industrial sites. [1] Building in existing built contexts necessitates a different approach to planning as well as special skills. Reliable and informative documentation is an essential pre-requisite for planning in general but especially for planning tasks involving existing buildings, where existing plans and building documentation are incomplete, very basic or not up-to-date. A look at current computeraided surveying systems reveals a serious lack of IT support for surveying and the preparation of the collected information for use in later planning stages. The consequence: current building surveying and planning working practice is characterised by: • a lack of simple tools for architects & engineers (see Figure 2); • surveys are limited to solely geometric data; and • the inclusion of a lot of redundant information 1. “Parallel to planning” Building surveying 1.1. Concept of a computer-supported building surveying system A building survey provides the basis for all planning activities in an existing context, it is the starting point and also an essential Aplicações Profissionais 21 Figure 1: Current building surveying process, Left: Building Surveying. Middle: Laser Distance meter, Total Station and Photogrammetry. Right: Geometry Model – CAD Figure 2: Situation on-site part of the entire planning process and the life-cycle of the building as shown in Figure 3. Based on an empirical examination of the planning process, existing computer-supported planning software and IT solutions as well as geodetic tools, we identified the following information characteristics for planning-relevant building surveying: • different types of information; • different ordering principles / structuring of information; and • different levels of abstraction and detail. In order to adapt this structure of information to the software architecture, we then analysed the surveying process itself to identify at which step of the process a certain detail of information is needed. 1.2. Analysis of the surveying process To minimise the time and money spent on surveying a building-site, we divided the entire work process into different steps. These steps are ordered in degrees of detail – each step offers the opportunity of enriching information density. At the same time, we ensured that the information collected in a given step is saved for use in later steps, according to the surveying targets in the appropriate surveying phases: 1. first site visit: information about inventory, identification of objects, visible damages; 2. sketch-based spatial information: sizes and volumes, sketches of building; 3. detailed ground plan: detailed analysis of building conditions; 4. exact 3D geometry; and 5. evaluation / check: acceptance of work and facility management. This research project is based upon the following assumptions for defining the optimal processes involved in computer-supported building surveying, modelling and building planning: • Building surveying will be integrated into the context of the planning process. • A building survey is not simply a geometric description of a building. In addition to a structured approach to measuring the building geometry, other formal, informal and relational data is also captured and stored within the information container – a semantic structure. Figures 4 and 5 show how geometric and semantic structure are separated. The geometric structure is linked with formal-descriptive data. • A data structure should be provided which is standardised for particular building types (basic templates). This data structure can be modified at run-time to fit the specific individual surveying and planning requirements as shown in Figures 6 and 7 [2]. Further aspects of the research project are described in [3], [4], [5], [6], [7], [8]. In essence, the concept aims to connect the surveying of relevant parameters with their use in the planning process. The integration of both is such that the individual tasks are no longer conceptually separable and the surveying and assessment of information can directly influence the planning process and vice-versa. The entire process occurs in direct face-to-face relation to the building being planned and the architect can actually work directly ‘on the building itself’, just as the master builders once worked. 22 Aplicações Profissionais Figure 3: Life-cycle of buildings Figure 4: Information container Figure 5: Geometric and semantic structure Figure 6: Flexible ordering structures 2. Software platform: A basis for different prototypes Based upon the analysis and identification of deficiencies, a system was developed with the aim of providing a set of tools for the computer-assisted surveying of buildings. These tools are designed as clients with different complexity and data processing capabilities and interact with a central server module. 2.1. Software architecture The system concept follows a modular principle to provide a continuous, evolutionary, flexible and dynamically variable system which addresses aspects ranging from the initial site visit to the preparation within an information module. Using client-server technology it is possible to integrate different modules (clients) for surveying and planning within existing built contexts according to requirements. (Figure 8) The server is used to store data permanently and centrally and interacts with various clients. Redundant data storage within the clients reduces the level of continuous data-transfer load on the server. The flexible concept of the software platform enabled us to create task-specific software clients that support certain work steps at certain phases of the surveying process. Thus, we could not only use different software modules at different times, but also on different hardware platforms that best suit the task to be supported. This flexibility allows for adapting the data representation, data input and output means, as well as the structures on how this data will be processed by the central server. 2.2. Prototypical Realisation The prototype of the software platform consists of a series of extendable tools which access and work with the same database. Figure 9 shows two examples of different client views of the same building data. For instance, support for the initial site visit (Figure 9): this tool allows the recording of formal attributes and for instance the derivation of estimated . Another tool provides a sketch-based, plan-oriented creation of simple building geometries and their adaptation to fit previously taken measurements. After the building geometry has been entered in sketch form the system looks for likely geometric abstractions. (Figure 10,11) Aplicações Profissionais 23 Figure 7: Different abstraction levels Figure 8. software platform with different clients connected to a central server Figure 9: Icon view – Recording of the spatial structure, technical and project specific parameters Figure 10: sketch-oriented view – Recording of the spatial structure and essential room-descriptive elements Using various different tools, manual measurements or measurements obtained with tacheometry or photogrammetry can be introduced into the model. The geometry is then adapted accordingly. Figure 12 and 13 show a room surveyed using different tools. Further aspects of the prototypes are described in detail in [9]. By integrating the software aspects into the interdisciplinary system design, we could demonstrate a holistic software architecture design concept that supports a new concept of building surveying. By then re-examining and redefining the software and hardware used for surveying itself, i.e. making the system “wearable”, we devleoped a new approach to building surveying which enables the user of the system to work “free hand”. 3. Modular Wearable Computer System for Building Surveying A current project takes these investigations one step further and examines the development of a concept for a practical, mobile, digital configuration and system environment – a wearable computer for surveying and planning on-site [10], [11], [12], [13]. Based on the server-client software architecture described in the previous section, we designed hardware systems for physically supporting the surveying process following the same modular concept in order to fit the software concept. 3.1. The Hardware Concept During surveying, there are different tasks which depend on what is being surveyed (see Section 2.2.). These different tasks require different tools, which the surveyor will carry with him on-site. Based on a division into five surveying t