Populating an iModel with Revit Models
So, here’s a quick one. This is by no means a fully blown guide on how to add Revit files to an iModel, this is simply a quick and dirty overview, guiding you through the sequence you’ll need to follow.
Some might know the famous Revit sample house. In my previous life, I often used this project to demonstrate Revit features during team training. Geolocating projects in Revit isn’t the easiest and there are multiple ways to achieve this. Almost everyone has a slightly different approach to this.
In case you have Revit available here’s where you can find the sample file:
C:\Program Files\Autodesk\Revit 2019\Samples
rac_basic_sample_project.rvt
I chose a random location in the middle of New Mexico as I didn’t have any other site information available.
The Building Site (someone’s property?)
In the UK we use Ordnance Survey (OS) coordinates but of course these won’t work here. Someone from the states probably knows more about US systems but I had the impression that every State uses its own coordinate system — sometimes even multiple ones!
Site coordinates are:
Latitude and longitude at: 36.388814, -105.621209.
I use this tool to convert these into Revit digestible northings and eastings (XY). Please note that we are using millimetres and metres.
This also works in reverse; in case you only have the XY coordinates available, but you will need to know your UTM zone. You can find that out here.
Revit geolocation
Add project coordinates to both: Project Base Point and Survey Point
- for PBP — leave clipped
- for SP — open clip to add details, close when done.
- add height to PBP
Note: some projects might require a different setup.
This is for Revit 2019–2020 doesn’t allow editing the Project Base Point directly anymore. Here you will need to use the Specify Coordinates at Point.
Location, Weather and Site
It is also important to set the site location precisely. Default location for new models in ‘Revit world’ is usually somewhere west of Boston, MA. This isn’t an issue unless solar studies are done with the model. To get a Revit files into iTwins the latitude and longitude coordinates must be set.
Revit Internal Origin
There is also a common misconception among Revit users, that having the Project Base Point and Survey point too far way causes inaccuracies. In fact, the software simply displays these coordinates without moving anything. What you still should avoid is having the model geometry too far away from your project base point. Version 2020 finally has the capability to reveal the internal origin.
Revit Bridge with iTwin Synchronizer
The most convenient way to align model into iModels is using the iTwin Sychnronizer, which can be downloaded from here.
Create your new iModels here.
And if you don’t have a Bentley account yet, you know you probably should.
Create a new iModel, give a name and select iTwin Synchronizer (for empty iModel). Once done, click Submit and your new iModel will be created.
iTwin Synchronizer
In the meantime, install and start the iTwin Synchronizer.
From the top drop-down menu pick your newly created project and create a new synchronization.
Now, name your synchronization and map it to your iModel. In case it doesn’t show up, click the refresh symbol.
Select your root directory and now it is time to map your files. We only have one for now, but you can of course map multiple files in one go.
Once you click next, the application will check for any Bridge updates. To check any installed Bridge versions, click on the little gear icon, top right next to your log-in badge. Under About you can check for any updates and install or re-install those manually.
Save the synchronize settings for later.
Kick of the synchronization process by click the sync icon.
I would recommend to automatically create a new Named Version — this will save a few click later.
Now that the synchronization process is complete, you can go straight to your iModel.
Spatial Root
You might have wondered what it is all about the little globe icon above the list of files?
The first file you select will act as a spatial root, which defines the exact project location. Any subsequently added file will follow these location settings. This can help to quickly add multiple linked reference files without necessarily acquiring the coordinates in your design application for each and every single file.
Verify Location
Use Measure Location tool.
Note: there is a tiny difference since the origin is in the center of the wall which cannot be precisely snapped to in Design Review. (bad choice of origin point in Revit from my side here).
Result
And here you can see the Revit house nicely geolocated in Design Review.
Let me know in case you want a tour.
Country specific coordinate systems
The above workflow works for international projects. Be aware that most countries and regions use their own coordinate systems and relying on UTM will not be enough.
UK Example
Recently I came across a client’s model where the geolocation failed, and the model ended up at the default Revit location near Boston. Inspecting the model coordinates revealed that Project Base Point has been set to UK OS grid coordinates using millimetres. Survey Point has been left unmodified. However, the location has not been set to match the Project Base Point. This resulted in having the model being zipped across the pond.
I would like to highlight that there isn’t anything wrong with this Revit setup as such. I’ve done exactly the same setup on dozens of Revit files in the past and all projects ended up being built at their correct locations. The location was usually only set to roughly match the site coordinates — still good enough to perform some initial solar studies. Important was PBP as it is also used for DWG and IFC exports.
Using UK OS Coordinates.
How about a holiday home in Scotland? Detailed OS plans in CAD can be purchased for a few pounds but in the absence of these, Google is your friend. I use grid reference finder to convert the latitude and longitude obtained from Google Maps to OS grid coordinates.
This time I only used the lat / long coordinates and the iTwin bridge is clever enough to locate the building at the correct location. However, without setting the PBP exchanging files with other applications won’t be possible.
As long as users are aware that they have to set the latitude and longitude location to match their project northings and easting, geolocating in iTwins should be very simple.
Sneak peak
As a long-term project, I am working on building my very own digital twin of our apartment here in London. Over the last two years I’ve been dotting around a series of sensors all over the apartment. These sensors measure temperature and humidity and can trigger certain automatons. Recently I started to make my own DIY sensors such as a light sensor, CO2 or a particle sensor. Eventually I would like to link all these sensors and their data into an iModel — but this will require the help of someone smarter than I am.
