Revit 2020.2 Coordinate Systems

Happy 2020 to everyone. You may notice that I have created a new look and feel for the site, the original site going back to April 2009! Hope you like the new logo and appearance?

Anyone who authors Revit models or works with 3rd party consultants that use Revit has surely experienced poorly coordinated models and struggled to understand why models do not federate and overlay as expected.

Many of these issues are simply down to a lack of understanding of the Revit coordinate system or properly communicated BEP’s, but these are fundamental to the correct setting out and coordination of projects. Revit 2020.2 offers some help by being able to visualise the Project base Point, Survey Point and the Internal Point within linked models. Also, you can no longer unclip the Project Base Point, meaning that the Internal and Project Base Point are normally consistent, however, see the note at the end of the post!

The image below is displaying the two Project Base Points, the blue being from the active project and the grey being from the linked model

Revit 2020.2 - Coordinate Systems

Revit 2020.2 Linked Project Base Point

Here you can also see that the Internal Origin point is also displayed in grey on a linked project. This is useful when checking that the Project Base Point and Internal Origin are overlayed.

Revit 2020.2 Internal Origin Point

When a linked model is selected the Project Base Point shows the linked model icon and the relevant properties such as the North/South, East/West, Elevation as well as the angle to true north. Very useful when trying to understand why Revit models will not federate and overlay correctly.

Revit 2020.2 - Linked Project Base Point

As many of you will already know, Revit has an internal origin which can be different from the Project Base Point. The Internal Origin point can now be displayed with a new sub category within the Site category.

Revit - Internal Origin Point

When setting the Project Base Point you should now use Specify Coordinates at Point or acquire coordinates rather than directly selecting the Project Base Point and moving.  You will notice that selecting the PBP and using the Properties Palette or directly typing the coordinates will move the PBP independently of the internal origin.

Specify Coordinates at Point

LawrenceH

Tutorial – AutoCAD Civil 3D Surface to Revit Topography

Over the next few months I will be posting some tutorials and workflows for taking civil engineering models such as drainage layouts and retaining walls from AutoCAD Civil 3D to Revit. The reasons for these workflows are to increase the Level of Detail and information that is held within the models. For example, the coordination and documentation of foundations with new drainage and existing underground services can be achieved very efficiently with the use of AutoCAD Civil 3D and Revit. This is even more relevant with the introduction of Autodesk Collections which will have Revit and AutoCAD Civil 3D available to all! See this link for a full list of products that are available in the Autodesk AEC Collection

https://www.autodesk.co.uk/collections/architecture-engineering-construction/included-software

In this first post I will concentrate on the fundamental task of getting a TIN (Triangular Irregular Networks) surface from AutoCAD Civil 3D to Revit as a 3D TOPO.

Triangulation

AutoCAD Civil 3D and Revit each use slightly different algorithms for the triangulation of surfaces. This could potentially allow errors to creep in if we simply rely on points and use these points to build surfaces in Revit and Civil 3D. In practice you should create the Revit Surface directly from the AutoCAD Civil 3D triangles. In the example below you can see a triangulation model from AutoCAD Civil 3D with the points shown in red and the levels shown in blue.

TIN Surface Original Trangles

In the image below the Revit Triangulation algorithm is shown in red. The points are connected in a different order and can cause minor differences in levels.

TIN Surface Revit Traingulation

To ensure that AutoCAD Civil 3D is showing triangles, select the Surface and then select ‘Edit Surface Style’ from the Right Click context menu. Select the Display tab, make sure that the View Direction is set to Model and ensure that Triangles are visible and all other component types are switched off.

Civil 3D Surface Style Triangles

Datums

To ensure correct coordination to Revit you should clearly mark a survey station that you would like to reference and also a project base point. An example may look similar to the image shown below.

Revit Project Base Point and Survey Point

Note that in the above example the Survey Point was unclipped and moved to the Station ‘ST1’. You could also leave the Survey Point at 0,0,0 which would be the OS False Origin. You should never unclip and move the Project Base Point as this can affect IFC datum and coordination with other models.

Coordinates can be given from either the Project base point or the Survey Point. You will also have to multiply the Easting and Northing by 1000 to take into account the scale difference between the Survey (in Meters) and the Revit Project (in Millimetres).

AutoCAD Civil 3D Export to AutoCAD

The TIN Surface in AutoCAD Civil 3D is a special object that cannot be used easily in Revit. The solution is to export the AutoCAD Civil 3D surface as an AutoCAD drawing. This will result in 3D Faces which can then be used to build the Revit Topography.

Click the Application Button, then Export and then Export Civil 3D Drawing.

Civil 3D Export to AutoCAD

The Export Dialog Box will automatically add a prefix to the drawing name to identify this as an AutoCAD drawing.

Civil 3D Export Dialog Box

One the export has completed the TIN surface will be represented as AutoCAD 3D faces. Make a note of the Layer that the 3D faces are positioned as this will be needed when creating the Revit Surface.

C3D to AutoCAD 3D Faces

Delete all other information and just retain the 3D faces and the datum’s as shown in the image below. The datum’s are very important for the coordination of the model within Revit. Scale the AutoCAD model from the Origin 0,0,0 and set the scale factor to 1000 (scale from Metres to millimetres).

Isolated AutoCAD drawing with 3D Faces and Datums

Revit Topography

Start a new project using your template in Revit. Make sure you switch to the site plan as the view range primary top and cut plane will be set to 10,000 to allow you to see the topograpgy.

In the Visibility Graphics/Overrides dialog box make sure that the Project Base Point and Survey Point are visible.

Revit Visibility Graphic Overrides Site Category

Next you link the AutoCAD drawing into Revit. Make sure that you set the import units to custom factor = 1 to ensure that there is no scale change. Also bring the AutoCAD file in Centre to Centre.

Revit Link CAD File Settings

Once the AutoCAD file has been linked it is a good idea to set the Visual Style to Wireframe to allow you to see the Setting Out information through the 3D faces.

Revit Set Visula Style to Wireframe

Unclip the Survey Point and move to the Survey Station of your choice (In this case STN1). Note that you will need to unclip the Survey Point, move to the location and then clip the Survey Point. I would then suggest pinning the AutoCAD drawing along with the Project and Survey Points.

Revit Project Base Point and Survey Point

Your Model is now coordinated!

To create the Topography, make sure that you first set the category to visible. Click the Massing and Site tab and select the Toposurface Tool.

Revit Toposurface

Click the ‘Select Import Instance’ from the context menu and select the linked CAD file.

Revit Select Import Instance

Do make sure that you now select the Layer where the 3D faces (triangulation) are positioned. You will now have a Revit Toposurface with Identical triangulation to your AutoCAD Civil 3D model.

Revit Toposurface From Civil 3D

Hope this helps,

LawrenceH

Revit 2018 – Geo Location Grid Coordinates from AutoCAD

In this short post I wanted to present a new key feature for the coordination of AutoCAD based data such as AutoCAD Civil 3D to Revit. AutoCAD has been able to utilise Bing mapping services to capture mapping and allow the coordination with many different coordinate systems since AutoCAD 2013.

Revit 2018 now supports this workflow by allowing consistent setting out between civil, structural and architectural disciplines using differing platforms.

AutoCAD to Revit - GEOLOCATION

If you have not used this feature within AutoCAD the process is shown below. The Set Location tool is found on the Insert Ribbon or you can type GEOGRAPHICLOCATION on the command line.  This can be set before any geometry is created or you could set this at a later date and then move your geometry to the correct ‘map’ position.

AutoCAD 2018 - Set Location

Once the Geographic Location command is started you can set the desired location marker and then click next.

AutoCAD 2018 - Set Marker

In the next dialog you can set the coordinate system that you want to use. In this case I have used British National Grid (OS) and set the units to millimetres.

AutoCAD 2018 - Coordinate System

Click Next and you then select a point for the location and point up the screen to set true north. Your model is now geolocated and you will see a map in the AutoCAD viewport.

You can now trace site boundaries, roads and any other features that you may require. IN the example below a few existing buildings and the new site are traced.

AutoCAD 2018 - New Site marked out

The AutoCAD DWG is then linked into a Revit project. If you are starting a completely new project then you can use acquire coordinates from the manage ribbon which will set the same British National Grid coordinates. If the project is already set up using the same coordinate system then you can simply link the DWG using Auto – By Shared Coordinates and the AutoCAD drawing will ‘land’ in the correct position.

In the image below another AutoCAD drawing is linked in by Auto – By Shared Coordinates.

Link CAD by Shared Coordinates

lawrenceH

Revit Structure Tutorial – Site Setting Out

In this tutorial we will explore the techniques and tools used to successfully coordinate a Revit project to a survey or OS grid. This process is often neglected which will cost you dearly later on! The problem is that this is only done once at the start of a project so is easily forgotten. A primary consideration is preparing a CAD file so that it is suitable for import into Revit. See Step 1! Get this wrong and the whole process will fail.

 Link to YouTube Tutorial : http://youtu.be/xlO7KF0vsS8

Revit Site

In a later tutorial I will outline the process of coordinating with Autodesk Civil 3D and a 3D TOPO but in this tutorial we will concentrate on a 2D survey, this could of course be in a variety of formats such as DWG, DGN or DXF.

1. The first step is to prepare your incoming CAD data for use within Revit. This will involve checking the UNITS of the CAD file (i.e. millimetres or metres), accuracy of the drawing and the layer configuration. If you have a very large survey then I would recommend using the WBLOCK command to select the relevant data and saving as a different name, this will clip a very large file. You will also need to check the extents of the file, if any data is outside your limits then delete (must not be greater than 20 Miles). At this point, freeze or turn off any layers that you do not want to be visible in Revit

AutoCAD - Preparing the survey drawing2. It is advisable to clearly mark a primary agreed setting out point on the CAD file that can be seen in Revit. This should normally be on a grid intersection and agreed and used by all Revit Buildings and disciplines (Construction, Architecture, Structure & MEP). If you know the consultants, architects and contractors who you are working with try and set up a Revit coordination meeting before any major modelling goes ahead to agree a universal setting out point that all Revit Buildings and models will use.

You can also create a secondary SOP for verification purposes. This should include the Easting, Northing and a level as shown below. If the structure is fairly large then you can consider increasing the precision of the coordinates. This is particularly useful for rotational errors that may occur.

Save the CAD file.

SOP1 setting out point - CAD

3. You are now ready to import the CAD file into Revit Structure. Once the CAD file has been selected you will need to configure the various setting within the dialog box. In most cases you will want to preserve the colours. Set the Layers/Levels to Visible and this will import only the CAD data that is on. Make sure that the units are set to the survey units, i.e. if the original CAD drawing is in Metres set the Import to Metres. The positioning should always be set to Auto – Centre to Centre. This will place the centroid of the CAD Building directly into the centre of the Revit Building (Note that this must not exceed 20 miles).

Revit Cad Link4. You will now move the CAD file to the Revit datum (0,0,0) position. The Project Base point will need to be visible; in the visibility graphics dialog box check the Site Category and then check the Project Base Point sub category.

Revit - Project Base Point

Once you have moved the survey your Building will look similar to the image below. Note that the project Base Point is now at the agreed setting out point (Some contractors may want to use the local agreed coordinate system on large sites for piling etc.)

Move the Survey to Project Base Point

You now set the Revit Site coordinates to match the CAD survey. Click the Manage Tab, Project Location, and Specify Coordinates at Point and select the Project Base Point. Enter the Easting’s, Northings and Elevation.

Set Coordinates

Coordinates

5. Save the Revit Building as the ‘Site File’. You will later insert your Revit Buildings into this file and acquire the coordinates.

6. You now prepare the Building file. Create a new Revit project with your active template and then make the Site Plan current view.

Revit Site Plan

Using Visibility/Graphic command (VV) switch on the Project Base Point.

7. If you have a DWG with the grid and architectural features then import this into the current view using the same rules as when importing the site plan. Move the Building to the agreed setting out point (Grid Intersection). Add a Spot Coordinate to the project base point, this should read 0,0

Model on Agreed Grid Intersection

8. Save the project as the Building File (e.g. Building A)

9. Open the Revit Site File and then import the Revit Building File by selecting the Insert Ribbon and then the Link Revit command as shown below.

Link Revit File

The Linked Revit File will now appear in the centre of your site file. Move and rotate the file to the Project Base Point to match the setting out of the grid. If you are new to this procedure then be sure to watch the tutorial video.

10. You will now acquire the coordinates from the Site file and record these into the Building file. Select your linked Revit file and in the Properties Window click the Not Shared button as shown below.

Select Linked Building File

Once the Not Shared button is clicked you will see the Share Coordinates dialog box. Use the first option which will publish the Shared coordinate system of our site file into the Building file.

Share Coordinates - Publish

11. Close the Site File and Open the Building File. You will see a dialog box asking if you want to save changes, click yes.

12. Open your Building file and return to the Site Plan. You should now see the correct coordinate system and if you change the Orientation from Project North to True North you will see the Building rotate to a True North position.

Building File - Coordinates12. Because the Revit Building file is linked, if the Building file is moved within the Site file then this will be ‘pushed back’ to the Building file and all coordinates and levels will be updated.

Tips and Tricks

Don’t forget to change your Levels to Survey. This will ensure that your project levels are always synced to the Site. Any changes to the site will instantly update the Building files.

Levels set to Survey

Don’t forget to watch the Tutorial Video, a lot to take in!

LawrenceH

Setting Correct Structural Levels

 This may be a simple post and many of you may already be aware of the following but I am going to post it anyway! When modelling in Revit you will have a tendency to start at Level 0 but will later receive the correct or revised levels and need to change the levels. There is a simple way of achieving this rather than trying to move the entire structure, you can simply change the elevation base to shared.

In the above image you can see that the base level is set to 0.00m. To change this to the new required level, click the Manage ribbon and choose Coordinates – Specify Coordinates at Point. Click the Level you want to specify and then you can enter the correct level.

Nothing will change until you change the type properties of the Level and any Spot Levels you have on the model. Select a level and then choose type properties. You will need to change the Elevation Base from Project to Shared. This will then update all the levels within your project. You will need to also do this for your spot levels.

Hope this helps,

LawrenceH