High-detail modelling of Grand Canal’s palaces: What VMX-250 mobile data can be used for
As already mentioned in the last newsletter in January 2011, the RIEGL VMX-250 Mobile Scanning System including the Modular Camera System VMX-250-CS6 was mounted on a boat in Venice, recording high resolution scan- and image data from the facades of the palaces on both sides of Grand Canal.
Now, with first facade outcomes available, it can be stated that the system has proved successfully its ability to both scan and photograph the facades with high resolutions in very short time. The quality of the acquired data is more than sufficient for producing a 2D-CAD map of a facade within a day, respectively a 3D-CAD map of a facade within two days.
The main goal of this project, which has been conducted in co-operation with the Universitá IUAV di Venezia, Lab System, CIRCE Photogrammetry Lab (www.iuav.it/homepage), was to survey the facades of all palaces along Grand Canal as a whole for the very first time by means of laser scanning.
Furthermore, by co-operating with the companies EKG Baukultur GmbH (www.ekg-baukultur.com) and PHOCAD Ingenieurgesellschaft mbH (www.phocad.de), the registered photos and point clouds were assessed regarding their suitability for further processing. Based on the orthoscans of the facades of the palaces „Casa d’Oro“ and „Casa Pesaro“ EKG Baukultur drew exemplary 2D CAD maps. Using the „Phidias” software, PHOCAD created an orthophoto and a 3D CAD model based on the RiPROCESS project.
Jan Kanngießer and Mathias Ganspoeck, CEOs of EKG Baukultur, both on the spot of data acquisition with the RIEGL team, agree after post-processing:
"The quality of the RIEGL Mobile Scans of the buildings of Ca'd'Oro and Ca'Pesaro on Grand Canal was by far sufficient to create plans on a 1:100 scale. The internal data evaluation lead to the outcome that the accuracy of the CAD models meets approximately level 2 – 1 of ÖNORM A6250, whereas the density of the information complies with level 3. Deformations, subsidence and other damages of the substance can be recognised easily and represented according to shape. We are convinced that for many applications in practice, there is no other method that is more efficient in capturing data from that many different facades within such a short time frame."
Christoph Effkemann, CEO Phocad, also appraises the data: "The scan density and image quality of the mobile laser scanner system RIEGL VMX-250 are very high, so that the data is not only suitable for simple city models but also for highly detailed architectural models and orthophotos. With an absolute accuracy of a few cm and image resolution of 5 mm in 20 m distance, the data is suitable for many different applications. We have shown that high resolution orthophotos and possibly detailed 3D building models can be created efficiently, which serve as the basis for restoration and research about history of architecture."
An article on the whole project starting with data acquisition and resulting in really impressing 2D and 3D deliverables was published in the April issue of GIM International.
To get an insight into data acquisition in Venice, a first impression of the giant extent of the fascinating point cloud, and an outlook on the resulting opportunities for future elaboration, watch the video on YouTube.