Multipatch Features and Drone Imagery; A Success Story
How five images can create a detailed and accurate building
The picture shown to the right is an orthomosaic of the Purdue Beef Unit. This was the chosen study area to fly the missions. The barn outlined in black is the building of interest that was focused on for 3D modeling.
Barn of Interest used for 3D Modeling
The weather was ideal conditions and the flight took 9 minutes to fly using a Mavic 2 Pro. This orthomosaic was used as a footprint for reference when creating the 3D model in ArcPro.
There are several ways 3D models have been previously created. One of the most popular ways to produce a 3D model is using photogrammetry software, like Pix4D. An Unmanned Aerial System (UAS) would fly around the object, collecting an excess of photos to use for reference points, then the software would stitch them together, creating the dense point cloud.
Downsides of this method are the time consumption as it has to process all of the photos it previously took. Furthermore, it is very common to have background noise, which interferes with the 3D processing and creates imperfections in the model. In the picture referenced to the right, the clutter that seems out of place is the background noise referred to.
Background Noise within the model
This 3D model consisted of 90 images orbiting the barn at 16m. The overall time it took to set up the UAS platform and run the mission took 8 minutes, however, process time took 40 minutes not factoring in re optimization to remove background noise.
Knowing just the dimensions of the barn, the multipatch feature in ArcPro can be used to quickly create a 3D model. Multipatch is a feature in ArcGIS Pro that allows the user to create 3D models by entering the dimensions and raising the structure. Multipatch is a great feature to bridge together the CAD and GIS world. The picture to the right shows the barn when initially created. Although this model is accurate to the actual dimensions, it does not look like as it would if seeing the barn on site. This is where pictures of the barn can be very useful.
By taking a picture of each face of the barn, they can then be put into ArcPro and placed on their respective faces. 5 photos were taken for this mission, 1 picture for each side of the barn and 1 picture of the roof. The overall time it took from unpacking and setting up the UAS platform to taking the needed 5 pictures was 8 minutes, however, the big advantage is the processing time. Rather than waiting for photogrammetry software to stich together the pictures, the 3D model can be created within a fraction of the time.
The final result is a finished 3D model of the barn. One of the big advantages of using multipatch is the decrease on time it takes to create a finished project from taking the pictures in the field to processing and creating the 3D model. The combination of versatile UAS platforms and the multipatch feature makes creating 3D models easier and more efficient than ever.
The next step is to use multipatch to create more complex structures and take accurate time stamps on how long each process takes from start to finish. The process will be repeated several times for redundancy and to mitigate outside factors.
