Fitting together pieces of a puzzle

Author: Walter and Martin Pilhatsch, October 2016

The Bonner Münster (Bonn Minster) is one of the oldest churches in Germany. A major basilica in Bonn’s old city centre, the existing structure of the church dates back to the 13th century. The ravages of time and poorly carried out restorations due to lack of proper structure documentation, have all left their scars on this historic building. Add to this the severe damage caused by an air raid in World War II, the Bonner Münster is in an alarming state and long overdue for extensive renovation. It was decided to call the engineering office of Walter and Martin Pilhatsch, located in Bonn, Germany, to collect and analyse data on the Bonner Münster church. Three generations of geodetic measuring experience combined with knowledge of 3D laser scanning, UAV aerial surveys and photo data analysis, made Pilhatsch surveying team the best choice for this complex job. Using the Leica ScanStation P40 and HDS7000, the team could complete a comprehensive 3D scan of the immense and complex building in the very heart of Bonn’s city centre.

It was very important to understand the structural damage to the Bonner Münster in order to correctly restore the church. For this, a highly precise 3D scan of the exterior facade was needed. This data helped support planning with the historic preservation authorities and calculate restoration costs.

Detailed 3D laser scans were required to create the floor plan of six levels and 12 different building sections. To accomplish this data collected from the project’s different sensors, such as Leica Geosystems' ScanStation P40, MS50 MultiStation, TS15 total station and an Unmanned Aerial Vehicle (UAV) needed to be efficiently linked.

Like a puzzle, the different data needed to fit together to build the model based on the geodetic network. Using precise TPS measurements from the TS15 and MS50, a basis for combining the scan data with the national coordinate system was created to become the foundation for this highly accurate geodetic network used to aid in the restoration of the church.

Height points were also connected to this network using the precision of a Leica DNA03 level. The actual surveying of the Bonner Münster was accomplished using a HDS7000 scanner and the latest ScanStation P40. The data of the façade’s towers and high roofs was collected using a UAV with a Sony a6000 camera. These acquired images were then adjusted and geometrically rectified so that the image proportions were not distorted.

Explore next chapter: Part 2