Interest in digital twin technology has steadily increased in recent years, according to data from Google Trends. In addition, I myself get more and more questions from clients who are curious about the possibilities. There are several reasons to build a 3d city model. In this blog, I discuss innovation as a trigger. Meerinzicht, a cooperation organisation of the municipalities of Ermelo, Harderwijk and Zeewolde, developed a 3d city model with the help of Kavel10 from an innovative idea: to test multiple applications in practice. Avineon is being brought in to provide texturing for the buildings in this 3d city model.
An innovation team within Meerinzicht suggested the idea of developing a 3d city model four years ago. They enter into a multi-year contract with Kavel 10 to make this innovation desire a reality.
Services provided by Kavel10 include:
- Multiple sourcing of Nadir and Oblique images;
- Processing Nadir images into true orthophoto;
- Executing aerotriangulation;
The innovation team within Meerinzicht starts by creating animations that show what the possibilities are. Then a demo is built that gives insight into the hypothetical possibilities of a 3d city model for specific issues. For example: how well can you visualise flood plains in the region? Can you do better analysis of this based on this visualisation? Another example: what happens to the landscape when you place a wind turbine in a certain location? How much impact will this have on the surrounding area?
3DBAG provided with photo textures
The 3D BAG model, developed by Delft University of Technology, is used as the basis for the 3d city model demo. The 3D BAG model can be used free of charge. Meerinzicht's innovation team then wants to add textures to the PDOK base layer. The help of Avineon is enlisted. Avineon has a large team of Data Engineers in India who can texture a large number of buildings relatively quickly and at low cost. These textures of the buildings are created from aerial photographs.
Converting data to CityGML
As a first step, the source information of all buildings in the 3d city model is downloaded in JSON format and converted to CityGML format using FME. A CityGML feed contains all the necessary metadata, with information about roofs, walls and foundations and other things needed to texture a building.
Automatic texturing in Rhinocity
After all data is converted to a CityGML format, it is imported into Rhinocity. This software automatically creates a 3d model of all buildings based on the available metadata. After Rhinocity provides the exterior of all buildings with photo textures, the data is converted and imported into ArcGIS.
The texturing of buildings in Rhinocity is done fully automatically. This application is capable of automating thousands of buildings in one run based on aerial photos from two angles: nadir and oblique. The aerial photos used are provided with geographical metadata that also gives the position of the cameras. When automatically texturing, Rhinocity takes occultation into account. If there are buildings in the line of sight between the building and the aircraft, the software looks for a clear angle.
Avineon's Data Engineering team oversees the texturing process. While texturing is done automatically, the process nevertheless has a number of manual steps: finding sources, creating projects, starting batches and then uploading the output.
Avineon's data engineering team supervises the texturing process.
Manual texturing of custom JSON files
More insight started texturing some of the buildings in their ArcGIS environment before calling in Avineon itself. In practice, this job proved too labour-intensive and too specialised to be carried out within a real timeframe. The part edited manually cannot be downloaded directly in JSON format by Avineon because the ArcGIS data has been modified.
This part of the data is manually converted to a CityGML format in India. RhinoCity is then used again to model the buildings automatically.
The end result is a 3d city model where all the buildings have been given realistic exteriors with relatively little work. The end result can be admired here!
Can we think with you about developing a 3d city model? Then feel free to contact me!