Changing project coordinates in Revit primarily involves aligning your model's internal geometry with a real-world coordinate system. The most direct method, especially when you have known real-world coordinates for a specific point, is by using the "Specify Coordinates at a Point" tool.
Understanding Revit's Coordinate Systems
Before adjusting coordinates, it's essential to understand the three main coordinate systems in Revit:
- Internal Origin: This is the fixed, unmovable origin (0,0,0) of the Revit project. All elements are built relative to this point. It's invisible by default but can be revealed. You cannot change its location.
- Project Base Point: Represents the origin (0,0,0) for the project. It's the starting point for measuring distances and elevations within your Revit model. By default, it coincides with the Internal Origin. Moving the Project Base Point shifts the entire model relative to the Survey Point and Internal Origin.
- Survey Point: Represents a known point in the real world, such as a geodetic benchmark or a site survey marker. It defines the shared coordinate system for your project and linked models. Moving the Survey Point effectively shifts the shared coordinate system relative to your model.
Method 1: Using "Specify Coordinates at a Point"
This method allows you to set precise real-world coordinates for any chosen point within your Revit model, effectively establishing the relationship between your model's geometry and the global coordinate system.
Steps to specify coordinates at a point:
- Navigate to the Manage Tab: In the Revit ribbon, locate and click on the Manage tab.
- Access Coordinates Tools: Within the Manage tab, find the Coordinates panel.
- Initiate "Specify Coordinates at a Point": Click on the Specify Coordinates at a Point command.
- Select Known Origin Point: Click on a specific model element or intersection in your Revit model that corresponds to a known real-world origin point (e.g., a grid intersection, a property corner, or a building corner from a survey plan).
- Enter Coordinate Values: The Specify Shared Coordinate dialog box will open.
- Northing: Enter the Y-coordinate (North-South) value for the selected point.
- Easting: Enter the X-coordinate (East-West) value for the selected point.
- Elevation: Enter the Z-coordinate value, which represents the correct datum (Elevation) relative to your chosen survey datum (e.g., sea level).
- Angle to True North: Enter the angle from Project North to True North. This rotates the shared coordinate system so that True North aligns correctly.
- Confirm Changes: Click OK to apply the new shared coordinate values to the selected point.
Practical Insights:
When you use "Specify Coordinates at a Point," you are essentially telling Revit: "This specific point in my model is actually at these global coordinates (Northing, Easting, Elevation) and its True North is rotated by this angle." This action adjusts the Survey Point (which represents the shared coordinate system) to achieve this alignment, effectively "repositioning" your model within the real world without moving the physical elements in your model.
Other Ways to Adjust Project Coordinates
While "Specify Coordinates at a Point" is direct, other tools are crucial for comprehensive coordinate management:
- Relocate Project: This tool (under Manage > Coordinates > Relocate Project) allows you to move the entire model relative to the Survey Point. It effectively shifts the Project Base Point, affecting project-specific coordinates and levels.
- Rotate True North / Rotate Project North: These tools (under Manage > Project Location > Position) adjust the orientation of your project relative to True North or change the view orientation for Project North.
- Acquire Coordinates: When linking an external Revit or CAD file that already has a defined shared coordinate system, you can use Manage > Coordinates > Acquire Coordinates to adopt the shared coordinate system of the linked file into your current project. This is vital for multi-disciplinary collaboration.
- Publish Coordinates: Conversely, Manage > Coordinates > Publish Coordinates allows you to save your project's shared coordinate system to a linked model, ensuring other disciplines can link your model correctly.
Best Practices for Coordinate Management
- Establish a Single Source of Truth: Agree on a consistent coordinate system and origin point with all project stakeholders (architects, structural engineers, MEP, civil engineers, surveyors).
- Use the Survey Point for Real-World Alignment: Always use the Survey Point to align your Revit model with real-world survey data or GIS coordinates.
- Use the Project Base Point for Internal Project Origin: Use the Project Base Point to define a logical origin for your specific building (e.g., column grid intersection, main entrance).
- Document Coordinate Setup: Clearly document the coordinate system used, the reference points, and any rotations for True North.
- Regular Communication: Discuss coordinate changes or requirements in project meetings to prevent misalignment issues.
Summary of Revit Coordinate Points
| Coordinate Point | Purpose | Behavior |
|---|---|---|
| Internal Origin | Fixed, unmovable origin of the Revit software. | Cannot be moved. All elements are created relative to it. |
| Project Base Point | Defines the internal project origin for reporting project-specific X/Y/Z and angles. | Can be moved to define a logical building origin; moves the project geometry when moved. |
| Survey Point | Represents a known real-world point, defining the shared coordinate system. | Can be moved to align the model with real-world coordinates; moves the shared coordinate system relative to the model. |
