Using DWG underlay

When you receive a DWG file, there are two possible coordinate systems: the DWG uses the project agreed point at NTM/UTM coordinates, or it uses the project agreed Nullpunkt as origin.

You can easily check this by opening the DWG with AutoCAD and retrieving the coordinates (keyboard input DIMORD). If the coordinates are in the same scale that corresponds to the project agreed coordinate origin, the DWG uses NTM/UTM as the origin. If the coordinates are in the range of a few meters, the Nullpunkt is used as the origin. When you check the DWG, you can also simultaneously determine which drawing units, meters or millimeters, are used (keyboard input UNITS). In the screenshot, the DWG is in NTM and uses the drawing unit meters.

AutoCAD: acquire coordinates and units from your DWG

We generally recommend using a DWG with the Nullpunkt as origin.

If your DWG is in NTM/UTM, you have to convert the model to use the Nullpunkt. This can easily done by following these few steps:

1. Create a new, empty DWG with the corresponding drawing units. You can use one of the templates we have :

   U:\BIM-Revit\A-lab Autocad Library\Templates\acad_empty meters.dwt

   U:\BIM-Revit\A-lab Autocad Library\Templates\acad_empty millimeters.dwt

2. Insert your DWG with the negative coordinates of the NTM / UTM origin. You can find the coordinates of the origin as screenshot (JPG / PNG) in the project folder:

   U:\xx\xx-xx-xxxx project\01_INN\01_gjeldende_tegningsunderlag\KART\01_offisielle kart\projektsnullpunkt.png

Screenshot: agreed NTM origin

AutoCAD: attach NTM DWG with negative NTM coordinates

1. Bind the linked DWG and explode any blocks or groups (keyboard input EXPLODE) and remove objects far away (if there are some).

AutoCAD: bind the NTM DWG at negative NTM coordinates

AutoCAD: break groups and blocks into separate objects

You may need to EXPLODE blocks and groups multiple times!

1. After exploding all groups/blocks, check the coordinates. They should now be within a few meters and close to the Nullpunkt. You can save the file now.

AutoCAD: NTM DWG placed at the Nullpunkt (NTM removed)

1. Open your project in Revit and ensure that the Nullpunkt is set as the current coordinate system.

Revit: Nullpunkt as current coordinate system

1. Link your DWG, making sure to use the correct Workset and drawing units and select "Origin to Internal Origin" as the positioning and place it at your desired Level. Make sure the boxes "Correct lines that are slightliy off axis" and "Orient to View" are unchecked.

Revit: link your DWG

Also, ensure you have selected the correct Workset, turned it on, and made it visible!

Revit: Workset open

Revit: Workset visible

1. Your DWG now uses the coordinate system of the Nullpunkt as origin. You can pin it, and you're done.

Revit: DWG linked and pinned at the Nullpunkt