Shared Coordinates How To: Scenario 2

This article demonstrates how to set up shared coordinates in a model that is already in progress, but needs to be realigned to the established Shared Coordinate System (SCS). In general, you will likely find yourself in this scenario more often than Scenario 1. Be prepared that the steps in this article are considered advanced and assumes you already understand the fundamental basics of Revit.

Note: This method uses the Acquire Coordinates function.

Revit version 2018 was used to create snapshots in this article and also the sample files for download.

Read about Scenario 1 in an article we wrote here.

Read more about Shared Coordinates which we defined here.

Important Concepts You Should Know Before We Begin

1. Three important coordinate points in a Revit model that define its spatial orientation are: 1) Startup Location Point; 2) Project Base Point; 3) Survey Point.
2. A CAD file’s WCS origin aligns with the Survey Point in Revit.
3. Multiple Shared Coordinates can be acquired and saved in a single Revit model, overwriting a single Site, and all instances are recorded in a hidden location until the model is detached. This explains the phenomenon that once you have acquired Shared Coordinates from a model, you cannot reacquire Shared Coordinates from that model again until your model is detached.
4. The last acquired Shared Coordinates will always remain in the model even if the model is detached, which again explains why you cannot reacquire Shared Coordinates from the last model that you acquired Shared Coordinates from. You may have attempted this if you acquired the position incorrectly and wanted to make an adjustment.
5. This article assumes your model is a Workshared model and is able to be detached the model. If it is not, we suggest converting your model to a Workshared model for this method to work.
6. The difference between True North vs Project North.
7. Clipping vs unclipping of project base point and survey point.

You will need the following items:

1. Your model (YM);
2. Shared Coordinates Model (SCM), in CAD or Revit format. This is often a survey performed by a survey engineer, in CAD format.
3. A Reset Model (RM) in either CAD or Revit.
4. Level 0’-0” (or 0.00m) is drawn in your Revit Model.
5. Common elements will need to be drawn in YM and the SCM which will be used to align the models, such as lines, grid lines & or north arrow.

Abbreviations in this Article:

SC = Shared Coordinates
SCS = Shared Coordinates System
SCM = Shared Coordinates Model
RM = Reset Model
YM = Your Model

The End Goal

The goal is to align YM to the SCM to enable essential coordination functions such as importing and exporting drawings in such a way that they fall on top of other drawings without further adjustment. Any experienced architect, engineer, or any designer, knows how much less effort and pain there will be when drawings can import on top of each other at coordinates 0,0 without having to rotate and/or translate into place. It cannot be emphasized enough how important it is for models to be exactly aligned at the beginning of a project. Misaligned models are one of the largest time sinks in any project.

Shared Coordinates System

This article assumes that a Shared Coordinate System (SCS) has already been established. The best way to establish this is with a Survey performed by a Survey Engineer. If a survey has not been performed yet, a coordinate system can still be established without a Survey simply by establish a CAD drawing or Revit model as the Shared Coordinates Model (SCM) for the project. You may download the example Survey, link at bottom, which this article will reference throughout. To clarify, any CAD file or Revit model can act as a survey, which essentially a common file that all models align to.

Step 1: Detach your Model

Start by detaching your model that you wish to align. This is an important step and is often easily missed. While it is possible to acquire models without detaching, success is not always guaranteed because you or someone else may have tried to acquire coordinates from the model multiple times before. The key here is to remove all previously acquired Shared Coordinates except the last one (which as explained before, the last SC cannot be removed).

Note: When detaching a workshared model, 99% of the time choose the first option “Detach and preserve worksets”. The 1% is typically for BIM Managers when creating templates.

Step 2: Reset your Coordinates with a Reset Model

This step is the most important step. By using a Reset model, this will in a sense switch the Shared Coordinates System to another model before switching the Shared Coordinates System to the one that you want.

Optional step: You may wish to turn on visibility of your Project Base Point and Survey Point to see what is happening. Visibility settings are under the Model tab.

While the model is still detached, open a floor plan that is at Level 0’-0” (0.00mm) in your model (this is not essential but having a plan at level 0) makes it far easier to understand). If you don’t have a Level 0, create one now by drawing a level at level 0’-0” (or 0.00 mm for metric). Then link in the Reset Model with Origin-to-Origin settings (Download link below). You may choose manual origin-to-origin to control the insert location better.

Acquire coordinates from the Reset model by going to Manage > Coordinates > Acquire Coordinates. Click on the Reset Model. Notice how the survey point moves to the center of the circle of the Reset Model.

Your coordinates are now “reset” and YM is ready to acquire Shared Coordinates from the SCM.

Step 3: Insert and Align your Shared Coordinates Model

The idea in this step is to align the SCM inside YM. You may need to move and rotate the SCM until the orientation matches the YM. Once they are perfectly aligned, acquire SC from the SCM.

Follow the recommended settings in the snapshots below. This part is very important to execute accurately or you may need to start over from the beginning. Follow the steps according to the type of SCM you are using.

CAD File

Insert your CAD survey at level 0’-0” (0.00mm) and align the drawing horizontally by moving and rotating until the common elements align. Common elements can be as simple as a line drawn from the origin to a point near the project site, or grid lines. The rotation of the model should be rotated according to the direction of project north, the upright direction on the sheet.

Note: Orient to View is unchecked to prevent the CAD file from rotating. This is simply for control.

Revit Model

Insert your Revit model using Origin to Origin.

Note: DO NOT insert using Shared Coordinates, or else it will establish a Shared Coordinate link and you won't be able to Acquire Coordinates.

Position the SCM such that it is aligned vertically and horizontally with YM. In a section, check that Level 0 in the SCM is aligned with Level 0 in YM. In a plan view, position the SCM so that it is moved and rotated into the correct position.

Tips: Make sure you are using the align function to align the position exactly. This is very important to be exact because you don’t want to find out later that you are off by a fraction and this will cause all of your drawings to be inaccurate.

Step 4: Acquire Coordinates from the Shared Coordinates Model

Go to Manage > Coordinates > Acquire Coordinates. Click on the SCM. Your model is now aligned with shared coordinates.

Notice that if the Survey Point was clipped, it would move automatically to the WCS origin (CAD) or Survey Point (Revit) of the SCM, proving that the Survey Points are aligned. If the survey point is unclipped, simply type in 0s into the X, Y, & Z coordinates and the Survey Point will move to the WCS origin in CAD or Survey Point of the Revit Model. (add images of clipped and unclipped).

Congratulations

You have established SC in YM! If you have more models to align to SCM, repeat steps 1 through 4 in all models.

Test Importing Models with New Shared Coordinates

Test your new Shared Coordinates by inserting a CAD file or Revit model using the Shared Coordinates setting. Your models will land on top of each other if this has been done correctly.

Test Exporting a CAD file with Shared Coordinates

Export a CAD file with Shared Coordinates. In your export settings, make sure the coordinate system is based on “Shared”. To access Export settings, go to File > Export > CAD Formats > DWG.

Insert the exported CAD back into the SCM at coordinates (0,0,0) to verify that Grids A and 1 align.

Sample Files

Sample files have been provided in the download link below. The exercise is to establish SC in the ARC, STR & MEP models using either Site 1 (CAD) or Site 2 (RVT). Then link the models into each other using Shared Coordinates and verify that all grids line up on top of each other.

The Optimum Shared Coordinates Setup

The optimum SC setup is such that the startup location, project base point, and survey point are at the exact same location in Revit. This point shall be equivalent to the (0,0,0) point in CAD. The 3D geometry of the building shall be located relative to this point.

Note that the layout shown below is for demonstration purposes only. The building can be positioned in any direction and/or rotation around origin.

This setup takes advantage of both the Origin-to-Origin and Shared Coordinates orientation which increases importing and exporting functionality, and reduces alignment mistakes. It also allows automatic alignment for Revit models by Origin-to-Origin especially if they haven’t Acquired Shared Coordinates yet. This topic will be explained more in detail in the next post, “The Optimum Shared Coordinates Setup”.

Sub-Optimum Setup

If the Survey Point and Start-Up Location are not aligned, this is considered a sub-optimum setup but will still align your models as long as the Shared Coordinates system is used throughout the project. It is recommended to place the project base point where Grid A and Grid 1 intersect.

Tips: Align Project Base Point on Top of Survey Point

Unclip the project base point. Enter 0, 0, 0 into the coordinates of the project base point.

Errors: Coordinates System Is Already In Use

This may occur for a couple of reasons.

1. You have already acquired coordinates from this SCM before.
2. If you detached the model, the SCM was the last time YM had acquired shared coordinates from.

To resolve, detach the model and acquire shared coordinates from a Reset Model to reset the Shared Coordinates System. Then acquire coordinates from the SCM again.