Portfolio: UAV-based Diagnostics of Structures

UAV and Cameras

We use high-end last-generation professional flight systems Falcon 8 by Ascending Technologies. Some important features of these Unmanned Aerial Vehicles are:

• Extremely stable platform even in strong gusty winds
• Autopilot Asctec Trinity
• Payload capable of mounting professional grade SLR camera equipment
• 360° camera field of view
• GPS and altitude controlled flight modes for outdoor and indoor missions
• Advanced navigation planning for semi-autonomous flight and data acquisition of large-scale structures and terrains

The camera technology includes both still and HD video equipment:

•  Sony Alpha 7R (3mm full format sensor system camera with misc. lenses, 36 MP)
• Sony Nex5 (system camera with misc. lenses, 16.1 MP)
• Sony Camcorder HDR-PJ810E (video camera, 24 MP, Full-HD, 12x optical zoom)

Services

In numerous research and consulting projects we have been able to perform extensive inspections on structures using UAV and have continuously widened the scope of possible applications of UAV in structural diagnostics. Today we can offer a range of services that allow for a tailor-made documentation of structural state and change detection. Some of the possible applications and data processing methods are listed below.

Recent projects, examples of image data analysis and services offered by the company can also be found in our UAV brochure (download).

Documentation of structural state and identification of damage

• Outdoor and indoor flights and still photo acquisition
• Creation of overview photos, orthophotos, stitching of images to large scale complete-cover images
• Photo and video based damage identification, documentation and analysis

UAV-based Photogrametry

• Outdoor and indoor photogrametry
• Photogrametric image acquisition for creating orthophotos for scaled measurable site plans (project planning etc.), elevations (facades etc.)
• High-resolution ([mm] accuracy) geo referenced 3D point clouds
• High-resolution ([mm] accuracy) meshed geo referenced 3D models of buildings and structural members
• Geo referenced terrain models

Applications in Conservation of Heritage Structures

• Contactless diagnostics and damage identification of fragile structures
• Highly detailed image and video analysis of special structural members, sculptures and artifacts
• Data documentation for planning of rehabilitation and restoration works
• Continued diagnostics through regular data acquisition (e.g. monitoring of deformations and cracks)
• High-resolution ([mm] accuracy) geo referenced 3D point clouds and meshed 3D models of terrain (e.g. archaeological excavation sites) and historical sites (castles etc.)
• To-scale 3D models of structural members and sculptures

Construction site survey and surveyance

• Documentation of construction progress
• Site management, logistics and safety
• 3D point clouds and 3D models for assessment of geometric tolerances

Data Acquisition for Urban and Regional Planning, Project, Property and Real Estate Development and Marketing

• Aerial imagery (Overview, skew angle, plan and elevation)
• Video capturing (dynamic flight)
• Panoramas
• 360° spherical panoramas
• Virtual tours
• 3D terrain and bulding models

Reference #2: Retaining wall

Large retaining walls composed of natural stone blocks are used along roadways as embankment structures. A 650m long section at the motorway A4 near Jena was recorded by UAV semi-autonomously. The flight paths and camera shot positions and directions were pre-programmed and 280 aerial images were taken within 45 minutes on 4 flight routes.

With the images, a 3D model of the 20m high wall was created on the basis of a point cloud of 1.9 billion points. This model is stored and will be used in the future to detect deformations of the wall over time. On the basis of the photogrametric accuracy it has been determined, that deformations of 7mm and above can be reliably detected.

The project was performed in the following steps:

1. Mission planning of flight navigation of autonomous capturing of images to cover entire wall
2. Data acquisition without traffic interference on neighbouring motorway
3. Computation of orthophotos
4. Photogrametric 3D reconstruction: creation of a geo referenced 3D point cloud
5. Meshed 3D model with <5mm accuracy on each point (supported by reference points surveyed with total station and marked on the structure)
6. Data storage for future change detection (wall deformations) based on a repeat flight (trial performed successfully)

Reference #3: Anna Ebert Bridge

In 2016 a complete documentation of the historical Anna Ebert Bridge in Magdeburg was undertaken based on UAV data and photogrammetric analysis as preparation for significant refurbishment works on the bridge. Our scope included:

1. Mission planning of flight navigation
2. Complete image data acquisition using UAV
3. Generation of a geo referenced high-resolution complete 3D model of the bridge
4. Computation of orthophotos of side and top views
5. Preparation of stone drawings of the bridge elevations to support refurbishment planning
6. Preparation of high-resolution 3D models of all ornaments of the bridge
7. Preparation of fly-through documentation videos

Reference #4: Indoor flight and 3D model of a Sculpture

Indoor UAV flights at the Cathedral Halberstadt delivered imagery of several sculptures that were otherwise impossible to inspect in detail. A photo from within the cathedral is shown below.