UAV Structural Monitoring “Schiefer Turm”

7. November 2014
UAV structural monitoring

Historical structures suffer from changing environmental conditions resulting in damages. Thus careful monitoring and planning is required to protect those structures and to choose the right conservation measures.

Visual inspections of historical structures are very costly and require technical, logistical and personnel resources. In particular, hard-to-reach places require expensive equipment, scaffolding und qualified personnel. For this exact reason we have tested as a part of a research project the possibilities and opportunities of unmanned aerial systems (UAS) like the AscTec Falcon 8.

Small electric high-end multirotor flight systems equipped with high-quality cameras provide enormous potential for the use in structural monitoring. Aside from the visual damage detection, flight systems like the AscTec Falcon 8 can be useful for vision based surveying (photogrammetric analysis) and generate 3D structural models.

Show case – UAV structural monitoring: UAV imaging, survey, 3D modelling of the Oberkirche von Bad Frankenhausen – ”Schiefer Turm“ in 60 minutes.

Data representations:
1a Light point cloud (7 Mio.)
1b Dense point cloud (310 Mio.)
1c Polygon mesh (62 Mio.)
1d Shaded relief; segment of the high density point cloud

Ortho photo mosaics:
2a South side
2b East side
2c North side
2d West side
2e From above

Digital elevation model (DEM):
3 Absolute Orientation, 14 ground control points (North, East)

3D model:
4 3D printed 3D model.

Flight system:
Type: V-Form Octocopter “AscTec Falcon 8”
Flight time: 12–22 Min.
Velocity: bis 16 m/s
Tolerable wind speed: bis 12 m/s (GPS Mode)
Camera mount: actively stabilized

Type: Sony Alpha 7R – DSLM
Sensor: CMOS full-frame (36 × 24 mm)
Resolution: 7360 × 4912 Pixels (36,4 MP)
Pixel size: 4,89 × 4,89 μm
Focal distance: 35 mm
Calibration: None, consistent

Quantitative evaluation:
Number of images: 524
Visibility: > 9 images
Effective focal distance: 36,4 mm
Distortion: < 87 pix
Distance: ∅ 11,5 m
Resolution: 1,34 mm/pix
3D Resolution: 2,68 mm/pix
Image error: ∅ 0,51 pix
Control point error: ∅ 2,66 mm

Project flyer:

Project partner:

Forschungseinrichtung (Bauingenieurwesen)

Bauhaus-Universität Weimar

Professur Modellierung und Simulation – Konstruktion    Prof. Dr. Guido Morgenthal
Marienstraße 13, 99423 Weimar    +49 3643 584417 ///

Professur Computer Vision in Engineering    Prof. Dr. Volker Rodehorst
Bauhausstraße 11, 99423 Weimar    +49 3643 583773 ///

Hersteller Mikro-Flugsysteme (Mikro-UAS)    Dipl.-Ing. Michael Achtelik
Ascending Technologies GmbH    +49 89 895560790 ///
Konrad-Zuse-Bogen 4, 82152 Krailling

Ingenieurbüro für UAS-Anwendungen im Bauwesen    Prof. Dr. Guido Morgenthal
Guido Morgenthal Technologien im Bauwesen    +49 151 40511577 ///
Wilhelm-Külz-Straße 22, 99423 Weimar

The research project „UAS/UAV for structural monitoring of historical buildings“ is supported with funding from the Research Initiative Future Building from the Federal Office for Building and Regional Planning (BBR) (SWD-

This and further projects we show at the denkmal (European Exhibition for cultural heritage protection, maintenance and old building restoration; 6.–8.11.2014) in Leipzig.