How to produce a 3D BIM model using UAV and 2D source data

UAV's (Unmanned Aerial Vehicle) are used more and more for inspection and survey of construction sites and infrastructure assets. I have put together these brief instructions to help you include your UAV data in the 3D BIM model of your infrastructure site.

Collection and use of UAV data

Firstly, when surveying and inspecting a site, it is important to use UAV equipment that produces geopositioned photographs (i.e. that the photos include a GPS location and direction information). Presuming that the objective is to get comprehensive and accurate inspection data that covers the entire site, it is also necessary to take photos from multiple perspectives and as close to the target as possible. For instance, for capturing bridges from below, tunnels or any other structures in tight spaces, you would need a drone with rotating cameras.

The captured photography would then be processed further into textured 3D mesh models using tools such as, for instance, Topcon ContextCapture. You can save the model data in 3MX (ContextCapture) or OBJ (other softwares) format, after which the created model can be viewed and examined with a VDC Explorer BIM software.

IMAGE 1: Three simple steps to produce 3D models from geopositioned photography.

In the VDC Explorer BIM software a 3D model can be completed with planning and mapping coordinates after which it can be still further enriched with other planning data such as LandXML or IFC models. In addition to reviewing all your plans in one place, a 3D combination model allows you to showcase your project and can be shared publicly or privately with the help of a VDC Live model sharing platform. VDC Live contains GPS positioning and Augmented Reality functionality which makes it possible to review BIM models also on the site of construction.

Once your combined 3D BIM model is ready, you can save it in OBJ, FBX or DAE formats and use different visualization software and game engines in order to create high-quality virtual presentations and animations.

3D modeling based on 2D planning and map data

Despite the digital era, many of our source and initial planning documents are still either paper or, if electronic, PDFs. VDC Modeler software helps you to convert nearly any 2D source data into 3D format. In documents and maps, the designed sites are often described as areas, lines and point symbols. With VDC Modeler, you can define rules for your vector-based data and ‘raise your design’ to a 3D model. For instance, the wall lines of buildings can be converted into 3D mass models, and lines can represent either fences or simple road lines.

In case your 2D source data is not yet in vector format (such as for instance DWG format given by AutoCAD software), you can use AutoCAD software to digitize your data. For instance, rasterized PDF or TIFF images can be read and placed as background in AutoCAD, after which you can use lines and symbols to draw the elements you wish to model. It is good to use layers to separate different types of elements from each other.

IMAGE 2: Digitize your source data, convert vector-based data into a 3D model and create one comprehensive BIM model by combining available model data.

Once you then have your initial 3D model in place in VDC Modeler, you can add different surface materials and textures to it in order to make it look more like the real target to be constructed. The software contains a specific texturing feature that allows you to add textures , for instance, to the 3D mass models of buildings that you produced from your initial 2D source and map data. However, before adding textures on any existing 3D structures such as existing walls, it is a best practice to go and take photos of the walls and ‘straighten them up’ with Photoshop. Create square image files (i.e. texture files) and save them in JPG or PNG formats, each and every texture as their own file, and then add them to your 3D model in VDC Modeler one file at the time (i.e. one wall at the time).

VDC Modeler also allows you to cut and embed 3D modeled elements into broader BIM models. For instance, a BIM model of a road or a street can be embedded into a bigger 3D model of an area in a way that the designed road cuts a place for itself in the destination model.

VDC Modeler is an extremely useful add-on to Autodesk design software such as AutoCAD, Map3D and Civil3D.

An example of a model that combines CityGML, IFC and Inframodel designs

Source: City of Helsinki 2017, published via VDC Live model sharing platform

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