Subproject A – A Collaboration platform for the interactive, multidisciplinary planning of railway tunnels based on multi-scale models
The main research focuses of subproject A aims at the synchronous collaboration during the planning process of subway tunnels. Here, synchronous collaboration means concurrent modelling of different planers at the same time on the basis of one central shared model provided by a collaboration platform. In contrast to asynchronous collaboration, sophisticated runtime collision detection is inevitable in order to assure the model consistency at all times. Therefore, we were identifying several main topics needed to develop a collaboration platform within this subproject. First of all, the design of a sufficient multi-scale data model (containing various information such as geometry, semantics, GIS, BIM etc.) became necessary, which further allows to derive any representation (level-of-detail or level-of-abstraction) required by the involved experts. In a second step, based on this multi-scale model efficient methods and strategies for the synchronous collaboration were developed. For benchmarking and demonstration purposes, a prototypical implementation a so-called collaboration server was put into practice and tested for feasibility with several collaboration clients that have been integrated in common CAD tools (such as Siemens NX or Autodesk Inventor). Additionally, special emphasis was put on the development of methodologies concerning 'generic interfaces' allowing the involved planers to access and process external data sources (for instance GIS databases) – via the collaboration platform – during runtime in order to leverage (highly) accurate multi-scale modelling.
A new Multi-Scale Procedural Model
Naturally, one of the most important subjects in the planning process of inner-city subterrestrial railway tunnels is the geometric model respectively the geometric models. Nowadays, the different planners use their own planning tools to accomplish their specialized planning task, such as planning the concrete track course, the tunnel tube, the train stations, and the escape shafts, resulting in different models. To combine or modify these different models in later planning steps is an extraordinary complicated or potentially impossible task. To overcome this drawback in close cooperation with subproject B a new multi-scale procedural model was developed as a basis for common planning process (, , ). This model stores the several construction steps that make up the whole model in neutral format, which is necessary to provide the possibility for synchronous modelling process, in particular, when the several planners are allowed use the modelling tools they are accustomed to. Since the given planning context comprises many different scales – from the kilometre scale while planning the principle track course to the centimetre scale while planning a concrete tunnel tube section – the concept of different Levels-of-Detail has been incorporated into the new procedural model from the very start.
|Figure 1: Refinement of a procedural tunnel model using different
Levels-of-Detail (1st, 2nd, and 4th)
Synchronous geometric modelling via the Collaboration Server
To use this procedural model in a synchronous modelling process a collaboration server was developed. This server hosts the procedural model and provides the possibility for the several planers to join and work in collaborative sessions.
|Figure 2: Different planners working synchronously via the collaboration platform|
When joining a collaborative session the different planners firstly load the procedural model and translate the neutral commands in system specific commands according to the modelling tool they use. Then, every new modelling step is immediately translated in a neutral procedural command and sent to the server that instantaneously forwards this operation to the other participating stakeholders. Using this architecture the different planners are allowed to use the modelling tools they are accustomed to while always observing and working on one and the same valid and up to date geometry model ().
Consistency in the synchronous modeling process
To maintain the consistency of the geometry model during a synchronous modeling process the collaboration platform must prohibit contradictory modification operations. Therefore smart locking mechanisms using graph based methods were developed. In principle, the collaboration server locks an element as soon as one planner starts a modification. Clearly, since a modification of one element may impact its dependent elements all dependent elements must also be locked. The basis for this locking mechanism of certain elements and their depend elements is the acyclic dependency graph provided by the procedural model (, ).
|Figure 3: An Autodesk Inventor client modifies the track course.
The coresspondning tunnel section is locked for a Siemens NX user.
To avoid locking huge parts of the model in case of modifications strategies were investigated to split the comprehensive model into smaller sections in a consistent way. Thus, a certain planer can focus on a concrete section of the tunnel tube in a certain Level-of-Detail, whereby the collaboration platform ensures the consistency of the comprehensive model even if the single planners is only aware of this small part of this model.
|Figure 4: A complete tunnel model comprises four sub models|
Incorporating geodetic information
Obviously, geodetic information is crucial in the planning process of subterrestrial inner-city railway tracks. At present, these pieces of information are provided by different kinds of Geo Web Services. The universal description of these Geo Web Services is one of the main research goals of subproject D. The resulting description in form of so-called Geospatial Web Service Context Documents allows a unified, dynamic and generic integration of needed Web Services respectively the provided data into the planning process (, ).
One main task for the integration of Geo Web Services into the modelling process is to develop generic interfaces to be published by the central collaboration server. These interfaces provide pieces of information about available Web Services using the above mentioned Geospatial Web Service Context Document. The users can browse the available documents, download them, and use the contained metadata information in order to connect to the concrete GIS data server and then download the desired GIS data.
|Figure 5: Principle workflow for integrating a Geo Web Service|
To accomplish the concrete integration process that supports the above mentioned features a component structure was developed. The principle idea of this structure is to encapsulate different data sources, such as Web Services and procedural geometry models, into so-called part objects, which then can be grouped into assemblies. This idea results in a hierarchical tree structure as shown above.
|Figure 6: Composition of different parts and assemblies into a tree structure|
An example for the concrete integration of a so-called Web Map Service can be observed in the figure above. In this example, a procedural geometry model describing a section of the concrete track course of the so-called “Zweite Stammstrecke München” is dynamically superposed to a map visualizing the development plan around the central station in Munich.
|Figure 7: Assembly of a WMS-part showing a hybrid representation of aerial image and development plan and a procedural geometry-part representing a model of several underground railway-tracks|
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|||Borrmann, A., Flurl, M., Jubierre, J., Mundani, R.-P., and Rank, E.: Synchronous collaborative tunnel design based on multi-scale infrastructure models. In: Advanced Engineering Informatics, Elsevier, 2013, Status: Accepted for publication
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