How Swiss Federal Railways (SBB) Plans to Use Hill Scan, Drone Concord’s Latest Know-how – Drones Information

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According to the European Railway Performance Index, the Swiss Federal Railways (SBB) is the largest public transport and mobility company in Switzerland and the front runner in its class. SBB has set up a drone competence center to monitor a wide range of drone applications across the company. Currently over 100 specially trained pilots operate a fleet of over 80 drones in dozens of use cases for the SBB.

When collecting high-quality drone data, SBB uses the Drone Harmony software to make it easier to use and to create replicable data in complex use cases. A notable example is Hill Scan, the latest site inspection and map technology from Drone Harmony, which SBB is using to inspect rockfalls near railroad tracks.

Inspection of stone chips over the railway infrastructure

As part of regular maintenance work, SBB has to monitor the steep hills and slopes directly above the railroad tracks throughout Switzerland in order to identify possible stone and landslides that could endanger the railway traffic below. There are several methods of monitoring such potential rockslides and landslides, each with their advantages and disadvantages. Whichever method you choose, the main challenges in carrying out such work are the vast extent of these areas (sometimes several square kilometers) and the steep and rough terrain they cover.

SBB recently carried out a proof of concept to test a new approach, which is to use drone imagery to measure displacement, a useful metric for monitoring rockfall. The new method is designed to complement traditional methods such as on-time surveillance through to terrestrial laser scanning by providing more insight into the parts of the site that otherwise require in-depth scrutiny. Using the displacement map, inspectors can specifically prioritize small parts of the site with the highest risk and focus on climbing and rappelling in those areas rather than doing such work across the site.

Steep cliff over a railway in Switzerland that needs to be monitored regularly.

The displacement map is generated from drone images captured using the latest Drone Harmony technology, which is specially designed to collect data in very steep and uneven terrain Hill scan. After the data is captured, the images are processed with other software products to generate the final result. Specifically, photogrammetry processes process images that were recorded in successive surveys into orthophotos of the area. The orthophotos are then precisely overlaid to generate the displacement map (see image below).

These maps classify the inspection site into regions with high and low displacements. Areas with high displacements correspond to the higher displacement of coincidence points in the successive orthophotos.

map
Description is generated automaticallyA displacement map of a cliff in Brienz, Switzerland, created by SBB based on drone images. Yellow and orange areas correspond to parts of the cliff with the greatest registered displacement.

The image set is captured at different resolutions so that inspectors can visually examine the area at different levels of detail. In addition, a 3-D model of the cliff is often created to provide additional visual representations and to plan the construction of protective infrastructure around the cliff. It is planned that the generated 3D models will also be used for the change analysis in the future.

Collecting drone data around steep cliffs and uneven terrain poses a number of challenges. Nicolas Ackermann, Drones Development Engineer at the SBB Drone Competence Center, comments:

“Collecting the necessary drone data is a challenge for several reasons. In the past, there was no software solution that could automate flight planning. Standard terrain-conscious planning was not suitable due to the difficult and steep slopes. Hill Scan should solve this problem for us. We also love the simple and very visual workflow in Drone Harmony and the handling of terrain data in the cloud and the web app. In this way we can train dozens of pilots with different skills for this complicated task.

Nicolas Ackermann, development engineer for drones in the Drone Competence Center of the SBB

In addition to using Hill Scan to create flight missions for virtually any terrain profile, SBB will also benefit from Drone Harmony’s cloud solution to simplify the workflow. For example, the entire terrain data set that SBB uses to plan nationwide is saved in the Drone Harmony Cloud. When planning a mission to a new location, SBB inspectors only need to navigate to that location in Drone Harmony Web. From there, you can start planning immediately, while the critical terrain data is automatically streamed to the web browser, eliminating the need for file management and sharing. When the mission is calculated, it is simply saved in the Drone Harmony Cloud and automatically synchronized with all associated mobile devices, which can then be used to carry out the flight with Drone Harmony Mobile.

“There are numerous problem areas that we need to review on a regular basis. Most of them have regular heavy rains. Our goal with this process is to provide new surveillance tools for the traditional expensive and dangerous approach, including sending qualified personnel to monitor the site on foot or by rappelling from above. In the long term, in addition to the obvious safety and quality advantages of the drone-based workflow, we also want to save time and resources in performing these activities. “

Nicolas Ackermann, development engineer for drones in the Drone Competence Center of the SBB

Hill scan vs. terrain follow

Why don’t standard terrain follow-up approaches perform well? To understand this, one must consider what happens when terrain tracking is used on steep or unevenly sloped terrain. Traditional drone mapping surveys are based on grid missions that cover the area of ​​interest with nadir images placed on a grid. The distance between adjacent images is chosen to match an overlap parameter and the flight altitude is chosen according to the desired ground scanning distance (GSD – determines what area of ​​the surface is represented by each pixel in the image). Compared to a standard grid mission, Terrain Following improves detection by adapting the flight altitude to the local profile, which ensures a fixed GSD, but does not guarantee overlap consistency and the camera angles are not adapted to the slope of the terrain. Drone Harmony’s Hill Scan solves all of these problems. The following figure provides a visual comparison between the three methods and summarizes their properties.

Cliff inspection with traditional terrain tracking (left) vs. hill scan (right)

Another valuable feature of Hill Scan is its flexibility. Hill Scan can map a larger area with different elevation profiles without having to divide the region into regions that are coherent in terms of slope or azimuth. As a result, hilly areas can be mapped in combination with flatter areas in a single mission. In summary, Hill Scan is a powerful tool that can aid in a wide variety of inspection activities, such as: B. in assessing cliff stability, inspecting mine sites, dam inspections and much more. Martin Fuchsberger, CEO of Drone Harmony, comments on the relationship with SBB and the future of the technology behind Hill Scan:

Inspection of a mining site planned with Hill Scan

“We had an open discussion with SBB right from the start. We are pleased that the Drone Harmony technology offers SBB added value for such a safety-critical activity. It is important for Drone Harmony to align the technology with the actual use cases. Hill Scan is an important step forward, but for us it’s just a scratch on the surface of what the underlying technology can do. We anticipate we can expand it to many use cases in the future, including structural inspection for vertical infrastructures. “

Martin Fuchsberger, CEO of Drone Harmony

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