For Better Project Delivery: How Does ArcGIS Understand Revit Models?

In my consultation sessions, I often observe that one of the biggest challenges in today's AEC projects is the integration of BIM and GIS. The root of the problem lies in the communication gap between the two delivery teams, as they often struggle to understand each other's language and workflows. Therefore, the essential first step is to bridge this gap by facilitating a mutual understanding of the distinct terminologies and processes each team uses.

BIM serves as a primary source of GIS content in Architecture, Engineering, Construction, and Operations (AEC+O) projects. However, before BIM data can be effectively utilized within ArcGIS Pro, it must be assigned a coordinate system. This ensures that the spatial information within the BIM model is accurately represented and can be integrated seamlessly into GIS workflows.

Understanding Revit Location in ArcGIS Pro

ArcGIS Pro recognizes the geographic information embedded within BIM models, particularly those created in Autodesk Revit. Revit, as a leading BIM software, utilizes multiple points to define the location of a building model. These include the Survey Point and the Project Base Point, each serving different purposes:

1. Survey Point: This represents a known location in the physical world, such as a geodetic survey marker or the intersection of property lines. It is used to correctly orient the building geometry in a coordinate system, such as those used in civil engineering. In Revit, the Survey Point defines a reference for the survey coordinate system, and it is visually represented as a blue triangle in the model.
2. Project Base Point: This point establishes a reference for measuring distances and positioning objects within the model relative to its environment. It is also represented as a blue circle in Revit.

While ArcGIS Pro is capable of interpreting the geographic information from Revit models, the BIM and GIS teams must collaborate closely during project delivery. This ensures that the integration process is efficient and that the tasks are not overly burdened on the GIS team. When both teams work together, BIM teams can provide the necessary information, such as georeferenced building footprints in CAD format, to support the GIS integration.

Revit Geometry in ArcGIS Pro

ArcGIS Pro utilizes a BIM file workspace, which offers a geodatabase structure to organize BIM files. This workspace, along with its datasets and feature classes, serves as a valid data source for creating feature layers in maps and scenes within ArcGIS Pro. Additionally, these are valid read-only inputs for various geoprocessing tools.

In Revit, elements are categorized into families, and these families are included in the more general categories within the BIM file workspace. Their names appear as feature attribute field values.

Revit elements contain a wealth of descriptive attributes and design parameters beyond their geometric representation. ArcGIS Pro captures these parameters as feature class attributes. However, ArcGIS Pro field names must begin with a letter, whereas BIM parameter names can start with a number. In cases where a BIM parameter name starts with a number, ArcGIS Pro automatically prefixes the field name with the letter "t."

One key feature within the architectural dataset of a BIM file workspace is the ExteriorShell feature class. This derived feature class is created by ArcGIS Pro, aggregating BIM elements likely to represent the exterior shell of the structure modeled in the BIM file. The ExteriorShell is a multipatch feature that serves as the default visual overview of the building when added as a building layer or scene layer in ArcGIS Pro or other compatible applications like the web scene viewer.

Levels Revit Models

For Revit (RVT), ArcGIS Pro provides tabs—Levels for RVT that list vertical building floors or named elevations included in the file. For RVT files, a checkbox indicates whether the named level is considered the floor of a building structure, a designation determined by the BIM file author.

Handling Linked Files in ArcGIS Pro

BIM models often link to other files, such as CAD files added as references. However, ArcGIS Pro does not automatically include these externally linked files when the data is added as features to a map or scene. Users can still view the list of linked files for reference, allowing a better understanding of the data in its original context. If these file types are supported, they can be added separately to ArcGIS Pro for further analysis and integration.

Conclusion

The integration of BIM models with ArcGIS Pro is a complex but vital process in AEC+O projects. By assigning a proper coordinate system and understanding the geographic information stored in Revit models, project teams can effectively leverage BIM data within GIS environments. This integration not only enhances the accuracy of spatial analysis but also improves collaboration between BIM and GIS teams, ultimately leading to more efficient project delivery.