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KNOWLEDGE BASE

How to adjust the zero point of a Revit Project (Australian Height Datum)

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You can happily work in Revit without worrying about survey height data.

Indeed if you have started a project without any information about Australian Height Datum (AHD)  then you’ll usually just set the “ground level’ to zero and in a lot of cases this is sufficient for your documentation.

So what happens if you need to incorporate AHD heights into your Project? Thankfully the answer is quite straightforward.

Revit has a number of coordinate systems that you can use to report information about where your model is located. That whole topic can be a bit confusing but in this case, we will be using a point in the Project that is usually hidden called “Base Project Point”.  This is a point in space that can be moved around to reflect real AHD data.

Firstly, go to an Elevation View or Section View and look for a small circle and triangle somewhere in the view-port. If you can’t see them, click on the “reveal hidden elements” icon at the bottom of the view-port.

reveal_hidden_elements

You should now see the icons in cyan. The one we want to deal with is the circular icon.

Zoom in a bit to make the next step easier and hover over the icons. If they are on top of each other, use the Tab key until the tool-tip shows “Project Base Point”. Alternatively you can drag from left to right whilst holding the left mouse button and once you made your selection, click on the Filter icon to select the PBP from there.

The next step requires us to click on the little blue safety-pin icon – if we don’t do this then the next step won’t work correctly.

pbp_selected

We now have to move the PBP to the required height. This might seem a bit counter-intuitive but it actually makes sense.

Let’s say that the site “zero” is really 5000mm about the AHD zero. With the PBP still selected, activate the move command. Now click anywhere on the view-port and move the cursor downward – you can either drag it to the desired distance or type into the keyboard and hit enter.

move_pbp

pbp_moved

So we can now see the PBP is reporting Elevation as -5000mm. Again, seems a bit confusing but the proof of the pudding is in the next image:

pbp_moved_Levels_updated

You will note that by selecting the PBP you will see a value for also see a value for Elevation as “-5000” (in this example) . You will also see a a value for “Angle to True North” if you have set True North to be different to Project North.

Note that you will need to make sure that your Spot Elevation and Spot Coordinates families are set to show “Project Base Point” if you wish for them to report with respect to this value!