Cartographic abstraction and obfuscation techniques for 3D city models for privacy protection

• Applicant: Professor Dr.-Ing. Martin Kada
• Subject Area: Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography
• Term: from 2014 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 253259060

As a result of the ongoing rapid developments in the field of sensor, analysis, and internet technologies, there is a continuous increase in the acquisition, presentation, and dissemination of geographical data. Especially for urban areas, there are already large-area photorealistic 3D city and street view models available on the internet for quite some time. The technological trend leads unstoppable towards more and more details and higher (image) resolutions. And there have been intentions advertised to systematically capture indoor environments. But besides all technical possibilities, it is easily forgotten that the systematic data acquisition of our surroundings and the derived realistic products out of it can also be perceived as an intrusion into our privacy. Especially if the deployed sensor platforms allow up to now unfamiliar viewing perspectives that overcome natural visibility barriers and therefore allow insights into our private living spaces. Furthermore, national security agencies and government representatives consistently express concerns regarding the presentation of security-relevant locations (government buildings, nuclear power plants, schools, churches, medical facilities, etc.) on the internet, which often results that the relevant areas are blurred or blacked out beyond recognition, thus lowering the applicability of 3D city models.In this research project, cartographic abstraction and obfuscation techniques are developed and applied in order to study and implement the protection of privacy and security-relevant areas with regard to the modelling, presentation and management of 3D city models. The objective is among others to translate the privacy measures known from the field of database management systems for handling personal data to the domain of 3D city models, without restricting their usage by the above mentioned filtering. Cartographic operations like simplification, aggregation, symbolization, typification etc. shall serve as elemental tools, which are (further) developed towards geometric and image based transformations of 3D building models if proven necessary. Besides the privacy requirements for affected individuals and facilities, the context, location, and authorization level of users, the semantics of buildings and regions, as well as temporal aspects shall be considered for the selection and configuration of abstraction and obfuscation levels. To dissolve the unavoidable occurring spatial privacy conflicts, geometric and image based conflict solving strategies as well as blending und rendering techniques are researched. The findings of the research project shall lead to the definition of abstract data types for spatial data bases and concepts for the integration of the developed abstraction and obfuscation techniques into the CityGML standard for 3D city models and into the OGC web services.

• DFG Programme: Research Grants