Creating a new ski jump complex
Author: Beate Wesenigk
Whether for the World Ski Championships, the Four Hills Tournament or the Alpine World Ski Cup, the Schattenberg ski jump in Oberstdorf in Bavaria, Germany, is the main venue for international ski jumping competitions each year. Refurbishment and new build work is being planned for the 53rd Nordic World Ski Championships in Oberstdorf in 2021. This will include a new "Einkehr" jump complex, named after the "Einkehr-Schwung", the existing culinary establishment facing the arena. ing-Geovision has created a digital terrain model (DTM) as part of the planning process.
Ski jumping on Schattenberg
In 1909, the first ski jump stage was built near Oberstdorf in Germany’s Allgäu Alps. Beautifully situated on a sunny hillside, after some initial scepticism, the sport was received with great enthusiasm. During the very first year, Bruno Biehler set the record jump at 22 metres pushing the limits of the facility. Plans for a new jump were devised at the start of the 1920s.
The new Schattenberg ski jump was used for the first time on 27 December 1925 – it is now 93 years old. The jumps and surrounding terrain have been modified and expanded repeatedly over the years. To improve the ski jump track for the 53rd Nordic World Ski Championships in 2021, the facility will be refurbished.
Challenges: area size, accessibility and self-imposed targets
German surveying company ing-Geovision received the task to create a DTM required as a reliable basis for the ski jump complex plans. The firm faced several challenges:
- The size of the area to be recorded - approximately 270,000 square metres.
- Some areas of the hilly, wooded areas are, in addition, very difficult to access and cannot be reached with terrestrial surveying equipment.
- The self-imposed target of capturing all data within just one day.
Surveying 38 Alpine football fields in one day
The three-person surveying team set off early from Traunreut to Oberstdorf in Germany perfectly prepared with different surveying equipment.
Step 1: The control point field
The foundation for the survey of the terrain was measured with the Leica GS16 Smart Antenna formed from an existing six-point control field. The GS16 Smart Antenna minimised the problem of mountainous areas with valleys and woods, which shadowed satellite reception for the GNSS survey.
Step 2: Measure the control points, the profile and the riverbanks
While the control point field was being determined, the targets for the scanning and the control points for the fly over were being set with the Leica TS16 total station. The TS16 was also used in surveying the profile of the wood. In total, this method produced 900 individual points measured almost entirely on steep terrain.
Step 3: Laser scanning and panoramic photos
The Leica ScanStation P40 was used to scan the area with 36 standpoints. All round scans with a resolution of 3x3 milimetres at 10 m were recorded.
“The P40 ScanStation took just 3.5 minutes per standpoint and has the added advantage that the black/white target points are available in the office. The result was a very dense point cloud made up of a total of 2,036,358,871 individual points. Full-HDR 360° spherical images were also recorded at each scan in a matter of seconds. The pictures can be read by the Leica Cyclone laser scanning software without any further processing and used for registering and processing the data,” said Richard Steiglechner, head of surveying for ing-Geovision.
Step 4: Fly over
To better survey the vast area and to be able to record the sections that cannot be reached using other methods, a fly over was done with a Leica Geosystems Unmanned Aerial Vehicle (UAV). A flight plan was generated with the software supported by the UAV before the automated GNSS supported fly over took place, covering all the sloping terrain as well as any obstacles, such as the jump towers. The software calculated the waypoints of the desired flight path based on the flight altitude, the obstacles, and the required accuracy using Bing maps. A series of 643 aerial photographs were taken using the attached camera in the UAV.
The three ing-Geovision"aries", who are also trained mountaineers, captured the data of 270,000 m² at more than 4,000 of altitude in one day and store their instruments before dawn.
Prepare the measurement data from the sensors
The surveyed control and individual points from the GS16 and the TS16 were loaded by the experts into the national coordinate system via an ASCII file. The scan data from the P40 and the MS50 were later entered into the Leica Cyclone scanning software for registration. Additional options were selected for importing, such as filtering the point cloud to eliminate unwanted erroneous points.
“The combination of the Cyclone's sophisticated filter technology and the ScanStation's pulse measurement technique makes it possible to eliminate so-called mixed pixels, the hazy points that occur when the laser beam is split over an edge and an underlying surface,” said Steiglechner.
Ing-Geovision experts could automatically align the spherical 360° panoramic images with the point cloud and the true colours assigned at each scan point using the "fixed" option in Cyclone to transform the point clouds from each position into an overall coordinates system using target marks, cloud constraints (point clouds with identical geometry in the overlapping sections between two scans) and point standards.
“The target marks were collected directly in Cyclone. Identical cloud constraints, or sections, are automatically found by the 3D point cloud processing software. We could use a viewer to assist us in case of doubt,” said Stefan Nawrat, head of engineering surveying for ing-Geovision.
The result: a digital terrain model that perfectly fits
Once the data from the individual sensors was edited, all the individual points and the point clouds from the fly over were imported into Cyclone to join the already registered point clouds from the P40 and MS50 scans. All the points from five different surveying instruments were now combined in one software. Then, a visual check was made of the positional accuracy of the point clouds by cutting through the point clouds.
The collected point clouds consisting of 2.15 billion points was exported as a Leica JetStream project so the point cloud could be further used and accessed anywhere.
“This approach reduces processing time and the risk of errors as the data does not need to be constantly copied backwards and forwards and it ensures that exactly the same accurate information is available for all further processing stages in different programmes, be that AutoCAD, MicroStation, 3D Reshaper or Autodesk Revit,” said Bernd Hafensteiner, managing director of ing-Geovision.
To draw the ski jump complex in the CAD programme, the open JetStream point cloud was shared, assisted by the Leica CloudWorx point cloud plug-ins, simplifying the drawing of flaws based on the point cloud.
The DTM was created with 3D Reshaper, a software system for creating terrain contours and extracting ground and break lines.
“3D Reshaper purges the point cloud and creates a point cloud group that contains only the ground points, all in barely 30 seconds. Its comprehensive settings guaranteed our team precise results,” Markus Prechtl, head of surveying flights for ing-Geovision.
The DTM created in 3D Reshaper was transferred to the contractor as a DXF file. To give contractors access to the point clouds in a browser, an additional password protected area on the company's Leica TruView Enterprise server was set up.
To plan the new "Einkehr” jump in the Audi Arena in Oberstdorf, only a precise point cloud and a comprehensive DTM would do. Using Leica Geosystems’ technology, the ing-Geovision team provided the best foundation for the next 93 years and beyond of ski jumping on the Schattenberg ski jump arena.