Travel blog AGILE 2016 in Helsinki
By Florian Fichtner & Ivo de Liefde
Point clouds contain a wealth of potential information about scanned objects and surfaces,
but also about the space which can be used to move through. This empty space can be derived and structured swiftly and efficiently from point clouds using the methods we developed during the Geomatics Synthesis Project 2015, themed: ‘explorative point cloud processing’. In this project, three groups of students spent ten weeks building an application for either indoor, terrestrial or aerial point clouds. Our group, named ‘Project Pointless’, was to focus on indoor point clouds.
For generating models of indoor space, the focus often lies on identifying the boundaries of space and the objects inside it. But for indoor pathfinding it is much more logical to focus on the empty, pointless space, which is the space that can actually be used. Therefore, our group developed an algorithm which identifies and structures the empty space in point clouds. A linear octree was used to derive and structure the empty space. The octree recursively subdivides the point cloud into eight equal-sized octants, up to a predefined maximum resolution. Octants are called grey nodes if they themselves contain smaller octants. Octants are called black (containing points) or white (empty) leaf nodes if they do not contain smaller octants. This structure allows pathfinding algorithms to be applied on point clouds.
We had the opportunity to write a paper about this method and present it at the AGILE conference on Geographic Information Science in Helsinki, Finland. On top of that we presented two theses, which continued the research on structuring empty space in point clouds. The thesis by Olivier Rodenberg improved the performance of pathfinding algorithms in linear octrees. Florian Fichtner added semantics to the octree regarding floors, walls, and stairs. This enables the pathfinding algorithm to be constrained to human movement. Our approach was much appreciated. The audience provided us with interesting ideas for future projects.
Besides acquiring feedback, we were able to visit presentations about other research as well. It is inspiring to see what is happening in the geo domain at universities all over the world. The conference started with an interesting keynote by Menno-Jan Kraak about the importance of maps and the international map year ( http://mapyear.org/ ). Former Geomatics students Rusne Sileryte and Matilde Oliveti attended the conference as well. They presented their work on Volunteered Geographic Information (VGI).
The AGILE conference included a reception at the city hall and an amazing gala dinner on an island just out of the harbour. Our hostel included a sauna, allowing us to be fit for a long day of conferences, even after long nights in the city. After the conference we took some time to hike in the Noux national park and to visit the modern art museum. In contrast to the weather in the Netherlands, we enjoyed some of Finland’s beautiful landscapes (see https://goo.gl/maps/QbftZb5e59P2 ) with blue skies, sunshine and unfortunately lots of mosquitos.
We would like to thank our supervisors, co-authors, UFonds and other sponsors. Without
them we wouldn’t have had this great experience.
Broersen, T., Fichtner, F. W., & de Liefde, I. (2016) Pathfinding through Identified Empty Space in Point Clouds. In GIM Magazine 21.04.2016.
Broersen, T., Fichtner, F. W., Heeres, E. J., de Liefde, I., Rodenberg, O. B. P. M., Verbree, E., and Voûte, R. (2016). Identifying, visualising and pathfinding through empty space in interior point clouds using an octree approach. In AGILE 2016; 19th AGILE Conference on Geographic Information Science, 14-17 June, 2016; Authors version.
Florian W. Fichtner studied geomatics at Delft University of Technology and graduated at CGI. He is fascinated by maps and holds a BSc in geography from Tübingen University, Germany.
Ivo de Liefde has a broad interest in geosciences and is graduated from Delft University of Technology in geomatics. He obtained his BSc in human geography at Utrecht University.