Georeferencing workflows

The geoprocessing tools on the Tools page allows you to process Supported file formats in ArcGIS GeoBIM. Before you can even begin using ArcGIS GeoBIM, it is always best practice to have an information management plan in place for your data including a standardized project coordinate system and consistent units to ensure spatial accuracy . Accurately georeferencing your Autodesk Construction Cloud (ACC) project files ensures that when you run the ArcGIS GeoBIM tools, your documents, issues and project features appear in the correct location with the correct extent.

Choose a coordinate system

When creating an ArcGIS GeoBIM project, a basemap must be selected which defines the projection of your project. It is important to choose an appropriate basemap to accurately locate your ACC data in the real world.

A coordinate system is a reference framework that defines the position of features in 2D or 3D space. In ArcGIS GeoBIM, maps and scenes use coordinate systems to locate and display your data correctly on the earth's surface. Accurate positioning of design files is critical for a number of reasons:

• Ensures that designs align correctly with existing infrastructure.
• Allows collaboration involving multiple disciplines.
• Allows for effective spatial analysis of the project scope and surrounding regions.

If you have a survey or base .dwg, review the survey deliverables, title block or project brief. Alternatively, you can also open the .dwg in Autodesk Civil 3D, and enter the command MAPCSASSIGN to check if a coordinate system has already been assigned.

Verify units

It is best practice to verify your units before you start working on your project, as inconsistent units, such as feet and meters or U.S. survey feet and international feet, can cause misalignments if not handled properly.

To verify CAD drawing units in AutoCAD or Civil 3D :

1. Open a .dwg in either AutoCAD or Civil 3D.
2. Type the UNITS command.
3. Note the drawing's unit settings and close the window.
4. Type the DWGUNITS command to view the internal units.
5. Ensure the units match the setting from the UNITS command.

To verify project units in Autodesk Revit:

1. Click the Manage tab.
2. Click Project Units in the Settings panel.
3. Ensure that the length units match your site data.

Tip:

Revit uses feet by default, which is nearly equivalent to international feet. If your site coordinates are in U.S. survey feet, you may set Revit's units to Feet (Survey) in the Project Units. This avoids any discrepancy between international and survey feet, which can shift the model by a few inches when working with large coordinate values.

Georeferencing CAD documents

There are three options for georeferencing CAD documents.

Follow these steps to georeference CAD documents using Civil 3D WKID:

1. Assign a coordinate system in Civil 3D to define coordinates by WKID.
2. Save a coordinate system as a projection file and store it with documents in ACC.

Follow these steps to georeference CAD documents using a projection file:

1. Select one of two ways to set the coordinate system:
   • Export GIS data to CAD with WKID
   • Use ArcGIS for AutoCAD to define WKID
2. Save a coordinate system as a projection file and store it with documents in ACC.

Follow these steps to georeference DGN documents using a projection file:

1. Select Geographic Coordinate System Dialog
2. Save a coordinate system as a projection file and store it with documents in ACC.

Georeferencing Revit documents

There are three options for georeferencing Revit documents.

Follow these steps to georeference Revit documents using shared coordinates:

1. Assign a coordinate system in Civil 3D.
2. Link a DWG file and use shared coordinates.
3. Save a coordinate system as a projection file and store it with documents in ACC.

Follow these steps to georeference Revit documents using specified coordinates:

1. Use a surveyed or queried point for known location.
2. Specify coordinates at a point.
3. Save a coordinate system as a projection file and store it with documents in ACC.

To georeference Revit documents using geographic location Specify the geographic location to use Latitude/Longitude (or Map) to define project location.

Georeferencing IFC documents

Even though ArcGIS GeoBIM supports many IFC entities to georeference a model, follow these steps for the best results with IFC models:

1. See buildingSMART User Guide for Geo-referencing in IFC v2.0 and use the IFC 4.3 or IFC4 format where possible. As defined in the user guide, specify your project reference coordinates (Survey Point and Project Base Point in Revit)
2. For IFC 4.3 and IFC4 files, ensure that the IFC entities IFCSite, IFCProjectedCRS, and IFCMapConversion exist in the model. For instance, if you enter the EPSG code of the coordinate system and use the Project Base Point, Revit would export the optimal entities for the correct georeferencing in IFC.

If after running the Add Document Extents tool, the calculate bounding boxes of the IFC models appear in an unexpected location this could be caused by the following:

• The wrong reference coordinate system was selected when the IFC file was exported from the source authoring software (for example, Revit).
• Shared coordinates have not been published into all the files that are linked to a Revit model.
• A model has been placed far away from the origin (Survey Point in Revit) in the source authoring software.

To fix the coordinate system in the source models, check the export settings of the source software that was used to export the IFC model. Follow the steps below to check the export settings:

1. See 'Section 5: Embedding the Geo-Referencing Data' in the buildingSMART User Guide for Geo-referencing in IFC v2.0.
2. Consult the user who exported the IFC file from the authoring software.
3. Check the export settings of the source software that was used to export the IFC.
4. Check which coordinate system was selected in the export setting of the authoring software.

Georeferencing PDF documents

PDF files require embedded geolocation metadata to be correctly georeferenced in ArcGIS GeoBIM. Follow the steps outlined in Geospatial PDFs for best practice on georeferencing.

Georeferencing JPG documents

JPG files must include valid latitude and longitude metadata in their Exchangeable Image Format (EXIF) data properties to be correctly georeferenced. Photos taken on a smart phone or camera will usually be geotagged. To check if your JPG is georeferenced, open up the properties of the image file and look within the details for lat/long values.