Coordination between Understanding Historic Buildings and BIMModelling : A 3 D-Output Oriented and typological Data Capture Method

At the present, in trend of shifting the old 2D-output oriented survey to a new 3D-output oriented survey based on BIM technology, the corresponding working methods and workflow for data capture, process, representation, etc. have to be changed.Based on case study of two buildings in the Summer Palace of Beijing, and Jiayuguan Pass at the west end of the Great Wall (both World Heritage sites), this paper puts forward a “structure-and-type method” by means of typological method used in archaeology, Revit family system, and the tectonic logic of building to realize a good coordination between understanding of historic buildings and BIM modelling.


BACKGROUND
Measured survey of historic buildings not only includes suitable measuring and representing technology and effective management,but also experience, cognition and evaluation of historic buildings in science, humanities, technology and art.It is not a process of passive recording, but integration of value judgment and information filtering activity which is easy to be ignored due to the restriction of the traditional 2D-output oriented survey.3D image can be generated through comprehensive thought of the brain by the plan, elevation and section which is a fragment of 3D space.It is this continuous "translation" 2D-to 3D-based work that tends to ignore the 3D space relationship, constraint reference relationships between components and tectonic logic of building.
As BIM technology has been applied gradually and widely, it reflects the obvious advantages in data capture and recording.A way of thinking on tectonic logic of buildings is provided by Revit based on BIM that also actively contributes to active cognition, understanding of internal building logic.Therefore this paper puts forward a "structure-and-type method" to realize a good coordination between understanding of historic buildings and BIM modelling.

General idea
The route map of the "structure-and-type method" could be summarized as follows: 1．to survey a building in 3D based on typological method used in archaeology, Revit family system, and tectonic logic of buildings, taking each component or part as a unit; 2．to draw a "space-structure dendrogram" (abbreviated as "structure tree") and "component type dendrogram" (abbreviated as "type tree"); 3．to make sketches and take survey notes based on the structure tree, and use both of them to reinforce understanding and support data capture and BIM modelling.
The structure tree, through locating each component in its "stratification", reflects structure, articulation, and space relation between components.The type tree, omitting space relations of components, mainly reflects typological relation The International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-5/W7, 2015 25th International CIPA Symposium 2015, 31 August -04 September 2015, Taipei, Taiwan This contribution has been peer-reviewed.doi:10.5194/isprsarchives-XL-5-W7-283-2015between components, and essentially is an induction of dispersive components according to their shape and size, etc.
The structure tree is no longer limited to 2D drawings, resulting in a good understanding of tectonic logic of buildings.And the type tree can be drew out after vertical and horizontal comparison of similar components, which can help research construction style, age, regional inherited characteristics in a higher level.The investigation method mentioned above with the structure tree and the type tree regarded as core, is just the structure-and-type method.

Workflow
Based on case study of two buildings in the Summer Palace of Beijing, and Jiayuguan Pass, the workflow is summed up as follows: 1．to draw the structure tree through observation, analysis, and record of components from their reference relationships step by step and then make sketches; 2．to conclude and merge the structure tree to the type tree, and amend each other during comparison; 3．To measure typical parts based on the two trees; 4．to check and perfect the two trees with measured data and prepare for the "family plan" for BIM modelling in Revit; 5．to perfect and form a chart and a preliminary investigation report and get ready for BIM modelling.It is the basic modeling idea in Revit that assembles components according to the tectonic logic of building in "project manager".Meanwhile, these components must be given a classification system, which can be described as "category-family-style" layer by layer.Among them, the family is the most vital.In Revit, the family is indispensable, as information model can't exist without the family.In other words, it is absolutely necessary to classify components during modelling in Revit.So based on requirements of survey and measurement about historic buildings, organized classification of components measured should be carried on, as their own characteristics of historic buildings, with the help of typological methods.
Therefore, it is supposed to consider its position in components of the same kind, and the family and type should be classified in preliminary.For instance, all the columns of The Great Theater

Methods
Induce and organize the family and type in the structure tree of each building, and map them into categories in Revit, with its hierarchical nodes as following: category-family-type.

CONCLUSION
In summary, the structure tree is a representation of the whole building construction process based on tectonic logic of This contribution has been peer-reviewed.doi:10.5194/isprsarchives-XL-5-W7-283-2015

Figure 1 .
Figure 1.The structural tree and the type tree

Figure
Figure 3.The hierarchic order

Figure 4 .
Figure 4.The units structure tree

The
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Volume XL-5/W7, 2015 25th International CIPA Symposium 2015, 31 August -04 September 2015, Taipei, Taiwan This contribution has been peer-reviewed.doi:10.5194/isprsarchives-XL-5-W7-283-2015 in the Summer Palace can be divided family of 3 kinds owing to their different section form when we ignore the mortise-tenon.According to this, all the inner columns and eave columns of the second floor can be classified as "circle column": the eave columns of the third floor can be classified as "square column" ;the eave columns of the first floor can be classified as "component column".