Augmented reality finds new applications every week. So far, those that have been proposed for the infrastructure world are generally either related to displaying hidden data (such as underground infrastructure models), or displaying attributes related with visible elements. If implemented on portable devices, such applications could be very useful for infrastructure operation and maintenance. There is, however, another aspect of infrastructure that could also benefit from augmented reality: construction. Recently we took some time to explore that possibility.

Construction drawings are the most important communication documents between the designer and the builder. For large infrastructure projects, there can be a very large number of them (sometimes thousands), each one referencing several other drawings through symbols and codes that indicate their relative spatial relationship. Because of that complexity, it may be hard to find the location a given drawing corresponds to in the physical world, especially on a building site. Builders may also miss important elements that the designer was trying to bring to their attention. Users tell us that drawings are a constant source of misunderstanding, and that they spend a significant amount of time trying to understand what the drawings mean. The use of drawings causes significant losses in time and may cause interpretation errors, which in turn may cause delays and errors in the construction work.

Yet, drawings are essential – they are still the only design document that is legally approved for construction. Consequently, even though designers may have produced detailed 3D models, drawings are the only form of design communication certified as reliable for construction.  Therefore designers, architects and engineers must take one dimension out of their 3D design and create 2D drawings.  Consequently, drafting essentially consists of a complex set of tasks aimed at accurately representing a 3D object with 2D representations.

Drawings are often misunderstood because they are abstractions. It is like working on a jigsaw puzzle, but trying to interpret any single piece of the puzzle by itself. Moreover, there are lots of drawings – so it is a non-trivial mental activity to reconstruct a set of abstractions into a coherent 3D representation of what is actually to be built. Paradoxically, although drawings are simplified representations of models, they are sometimes harder to work with…

In our most recent research work, we explored the potential of augmented reality for making 2D drawings easier to use on site. In particular, we investigated the problem of finding the physical location that a 2D section drawing represents. It would be interesting, for instance, to display drawings at 1:1 scale, inside the physical world, at the exact position they represent. This is an interesting problem to study, as section drawings often represent wall sections, which are quickly hidden (by the wall surface) as the construction progresses. Therefore, if we were to put the drawing at exactly the right scale and location in the physical world, it would actually be hidden by the wall itself…

This problem is reminiscent of the subsurface utilities augmentation problem.  Underground pipes are hidden by the ground surface – displaying them overlaid to the road surface is confusing. However, displaying them underground makes them invisible (hidden by the ground surface). To solve that problem, we proposed a compromise: to display them inside a virtual excavation. Therefore, we proposed a similar solution for section drawings.

In the following video, you will see 2 techniques that we proposed for making the visualization of 2D section drawings easier in an augmented context. The first one is a “sliding plane” technique – it slides the drawing’s plane at its exact location, to attract the user’s attention by indicating the location of the drawing. The second technique is similar to excavation: we cut through the wall, revealing the inside of the building (the model), and showing the 2D section drawing at exactly the location it represents, in a representation that retains full context, whilst allowing the 2D drawing to be fully visible.

Clearly in this visual representation, the result is greater than the sum of its parts: not only the 2D drawings can be interpreted more easily, but also can the 3D model and the physical world!  By displaying data this way, it is like taking a few puzzle pieces which, taken alone, do not mean much, and putting them together, in context, with the other puzzle pieces.  Together, they reveal the whole story…

This is our first baby step in that direction. Still, as you can see the technique seems promising.

Want to read more?  Check our paper:  Côté S., Trudel P., Snyder R., Gervais R., 2013. An augmented reality tool for facilitating on-site interpretation of 2D construction drawings.  Proceedings of the conference on Construction Applications of Virtual Reality (CONVR 2013), London, November 2013.  PDF

More to come! Stay tuned…

 

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