To help architects and civil engineers maintain consistent geographic location (geolocation) information between models, Revit can use grid (GIS) coordinates from a linked DWG file.
Suppose you use AutoCAD or Civil 3D to create a site for a project. In that file, you specify a geolocation reference point that uses GIS coordinates. When you link the site DWG file to a Revit model, the GIS coordinates are used to establish shared coordinates between them. The Revit model is correctly placed relative to the site. Also, the same GIS coordinates are used to define the real-world location (latitude, longitude) of the Revit model. This location is used for accurate energy analysis of the model.
Use one of the following workflows, based on your situation:
- When the survey point or the project base point is already defined using GIS coordinates from the civil engineer, link the DWG file using the Positioning option Auto - By Shared Coordinates. For details, see Link a DWG File and Use Shared Coordinates.
- When the survey point or the project base point is not yet defined, link the DWG file using the Positioning option Auto - Center to Center or Auto - Origin to Origin. Then acquire coordinates from the link. For details, see Link a DWG File and Acquire Its Coordinates.
Either workflow results in the following:
- Revit aligns the incoming site plan with the host model based on the shared coordinates.
- The Location tab of the Location and Site dialog indicates the GIS coordinate system, latitude, and longitude for the Revit model, based on the GIS coordinates from the DWG file.
In addition to positioning the model relative to the site, Revit uses the GIS information as follows:
- To specify the real-world position of the model
- During energy analysis of the model
- When publishing coordinates to other models
- When exporting the model to other formats
Positioning multiple instances of a DWG file
When a DWG file is geo-referenced, its geometry has fixed grid coordinates. When you link the DWG file to Revit using shared coordinates, the link's position is fixed in the grid coordinate system. You cannot use shared coordinates to link the same DWG file to a Revit model multiple times in different positions. If you want to use multiple instances of the linked file in the Revit model, after linking the file once using shared coordinates, you can link it again using another positioning option.