A world file (WLD3) is a text file containing control points that describe a coordinate transformation. The control points reference coordinates in the BIM or CAD file and the corresponding points in a matching spatial reference. For the transformation information to be useful, it needs a matching spatial reference file (PRJ).
The data comprises two sets of 3D points. Each row defines a displacement link using the following syntax: <From x,y,z> <space> <To x,y,z>. The first pair of coordinates in each row corresponds to the source coordinates, also known as the from coordinates. These values represent the x,y location of any known control point in the BIM or CAD drawing. The second pair of coordinates in each row corresponds to the destination coordinates, also known as the to coordinates. These values represent a new location in geographic space defined by the spatial reference of the BIM or CAD files.
The data looks similar to the following:
25933.063000,9032.704720,1702332.110159, 309622.102491,-8987.532001,1300.050854
32047.556994,13057.483520,1706354.400361 303697.073028,-9091.566340,1337.519601It is common for BIM or CAD design files to use a relative or local coordinate system rather than a geospatial coordinate system. In such cases, you need to define a spatial offset file (WLD3) to properly position your BIM data or CAD data. You will first need to define a spatial reference by including an Esri projection file (PRJ). Spatial offset information defines the offset from a known geospatial coordinate system defined in an existing PRJ file and the coordinates of your BIM data. A WLD3 file needs a matching PRJ file. The spatial offset information created by ArcGIS Pro georeferencing tools is stored in a WLD3 file with the same name as the BIM file. If the coordinates of the BIM model are based on the coordinates of an included PRJ file, there is no need to define a spatial offset using a WLD3 file and the georeferencing tools in ArcGIS Pro.
3D world files are saved with the file extension .wld3. Using a 3D world file to store control points is the best practice for sharing and reusing links in other projects and map documents. ArcGIS Pro uses the file name and its location to link the world file to a particular CAD dataset or Revit model. This file is similar to the 3D world file, but it contains a coordinate so the file can be placed in the appropriate x,y,z location.
To associate a 3D world file with a CAD dataset or BIM file, the following criteria must be met:
- The world file and the BIM or CAD design file must have the same name (prefix), for example, MyDrawing.RVT and MyDrawing.wld3.
- The 3D world file must exist in the same file folder as the matching BIM or CAD design file.
Universal 3D world file (ESRI_CAD.wld3)
The universal world file is a method for defining a single spatial transformation offset for a folder of CAD or BIM files that have the correct positioning relative to one another but need to be repositioned. The universal 3D world file defines the offset parameters for all BIM or CAD files that are stored in the same file folder and that do not already have a WLD3 file name that matches the BIM or CAD file name.
To use a universal world file, the following criteria must be met:
- The world file must be named ESRI_CAD.wld3.
- The world file must exist in the same folder as the CAD or BIM design files.