A practical look at surveying services for construction contractors, with a particular focus on major railway corridor projects
This article was featured in the August 2026 issue of the German Surveying VDV Magazine, written by Kossert, the Surveying Project Manager at Spitzke, a customer of GeoCue.
By Guido Kossert
On major corridor projects, it’s not only the volume of construction work that grows with the size and complexity of the project. The supporting services around that work grow as well. Surveying is a perfect example. It plays an important role before construction begins, throughout the work itself, and again at the completion of the project. Simultaneously, surveying teams are being asked to do more with tighter schedules and with fewer available specialists. New and more efficient technologies are helping close that gap. This article looks at several typical surveying applications in railway infrastructure construction.
How LiDAR and Other Technologies Are Changing Construction Surveying
On most construction projects, the contractor is responsible for carrying out or commissioning surveying services in addition to the construction work itself. That includes collecting supplemental data before work begins, supporting construction planning, providing data for machine control, establishing the design track position, and setting out a wide range of construction activities, particularly in civil engineering. Surveying is also required to confirm that the completed work matches the original design plans.
Depending on the size and complexity of the project, the need for up-to-date surveying data can be significant. Because much of this work takes place before construction begins, during breaks in activity, or after other phases are complete, it often goes unnoticed when a project is evaluated. Even so, it plays a critical role in construction accuracy and can have a significant impact on both scheduling and budget.
Staffing is an important part of that challenge. In the past, a larger surveying workload could often be handled simply by assigning more people. Today, qualified personnel are harder to find, so technology has become increasingly important. Systems such as LiDAR allow teams to collect far more data with fewer people and in less time.
These technologies also create opportunities that extend beyond the traditional measurement of site conditions. They can support areas such as material logistics, project documentation, and construction planning. At the same time, larger datasets shift more of the workload from the field to the office. Processing can require substantial computing power, storage capacity, and reliable methods for transferring data. On large projects, datasets can quickly reach the terabyte range. Sensor technology is becoming more accessible, but it still represents a meaningful investment and must be planned accordingly.
Source for all figures: Spitzke SE.
Before Construction Begins
Contractors typically receive surveying data from the client, often as part of the overall design plan. The information may come from the client’s own records or from outside service providers. For major projects, DB InfraGO (the public-interest infrastructure subsidiary of Deutsche Bahn responsible for managing and operating Germany’s rail network and passenger stations) also frequently provides aerial survey data through its X2BIM platform. Even with these resources, a rail network of roughly 39,000 kilometers presents obvious challenges.
Existing records can vary widely, especially when they were created at different times or with different coordinate systems. Newer railway infrastructure data are generally based on the DB_REF 2016 standard, which replaced DB_REF 2003. In some areas, older Gauss Kruger data can still be found, and parts of former East Germany may contain records based on Krassowski ellipsoid projections. Because these systems do not align directly, corrections and careful checks may be required.
Older secondary lines can present another challenge. As-built information may be incomplete or missing altogether. Even when data exists, site conditions may have changed because of natural ground movement, reconstruction, or events such as the 2021 flooding. Corridor projects add another layer of complexity because the area being surveyed can be so large that months, and sometimes years, may separate the newest and oldest datasets by the time all information has been reviewed, collected, and processed.
That becomes especially important in locations where tight tolerances must be maintained, such as machine-controlled construction or station areas with specific clearance requirements. As a result, supplemental surveying before construction can vary greatly from one project to another.
Even when the starting data is good, additional measurements may be needed to answer specific planning questions. Potential conflicts may be identified during design, or the available cross sections may not be detailed enough to accurately represent the track geometry. On the Nuremberg-to-Regensburg corridor, for example, a planned realignment from the no-longer-permitted 3.5-meter track spacing to the 4.5-meter spacing required for new construction meant that fixed constraints, including bridges and mast locations, had to be evaluated very carefully.
The way surveying is organized depends on the task, the local environment, and how accessible the line is while it remains in service. Safety always comes first. On the Hamburg to Berlin corridor, where Spitzke worked with Leonhard Weiss on Lot 2, surveying in Spitzke’s assigned sections began more than six months before the main construction phase. One reason was the time required to process the newly collected data and compare it with the design and existing condition data. The Right Rhine corridor rehabilitation, which entered construction in July 2026, also required extensive advance surveying, although the amount varied by location.
Data Capture During Railway Operations
For an as-built survey or an update to existing datasets, a survey using a mobile mapping system, or MMS, can be an efficient option. On the DB InfraGO network, Trimble’s MX9 is approved for track surveying in accordance with Ril 883 [2]. Mobile mapping systems are typically built as multisensor platforms that combine LiDAR, cameras, GNSS, and an inertial measurement unit, or IMU. By combining these technologies, the position of LiDAR measurements can be determined accurately even in tunnels or other obstructed environments.
The IMU does require a minimum speed to produce reliable trajectory data. In general, the vehicle should travel above 40 kilometers per hour, although newer systems can provide good results at around 20 kilometers per hour. Stops should still be avoided because the measurement process may need to be reinitialized. That makes long distance MMS surveying more difficult during active construction, when tracks are occupied by construction operations and frequent stops are likely.
A mobile GEDO IMS system provides another option. Because it combines a track measurement trolley with IMU sensors, it is not dependent on continuous travel at a constant speed. Across the three corridor projects discussed here, both the MX9 and GEDO IMS systems were successfully used by Gi Consult as a subcontractor, or surveys were completed before the lines were returned to service.
MMS can capture a detailed picture of the track position and the environment around it in a relatively short amount of time. Minimum speed requirements can reduce resolution in some areas, so additional detailed measurements may still be necessary. Even so, surveying roughly 100 kilometers of track with MMS can often be completed in less than a day. As with many modern surveying methods, much of the total effort comes later during processing.
Where overflight approval is available, a drone equipped with LiDAR can also collect data while the railway remains in operation. This approach is especially useful in difficult to access areas because high point cloud densities can be achieved without requiring the operator to enter the track or danger zone.
Surveying Slopes
Slopes often combine several difficult conditions. Track sections may not be safely accessible from the outside, and the slopes themselves can be affected by geological movement or erosion. That means the survey may need to capture not only the track position, but also the full slope surface.
This may be necessary to plan a realignment or, as on the Right Rhine corridor, to support extensive slope stabilization work. In those situations, current survey data is needed for both design and setting out. An MMS survey run or drone flight can provide the base dataset. If more detail is required, the information can then be supplemented on a closed track using a rail mounted system or a handheld LiDAR scanner such as the system shown in Figure 3.
Explosive Ordnance Surveying
At first glance, checking a construction area for unexploded ordnance may seem unrelated to surveying. In practice, surveying can be essential, especially for railway electrification or overhead line renewal projects that require deep excavation.
On large corridor projects, it would be impractical to survey the entire track area for ordnance. A more efficient approach is to focus on the locations where earthwork will take place, such as future overhead line mast positions. Those locations must therefore be identified and set out in advance.
On the Nuremberg to Regensburg corridor, this work began almost a year before construction. Millimeter level accuracy was not necessary for the initial guidance of ordnance detection teams because the detection process itself includes a substantial safety buffer. That allowed the surveying method to be selected based on the local conditions and the most efficient workflow.
For most of the work, RTK rovers were used. With GNSS, they achieved an accuracy of about plus or minus 2 to 3 centimeters. Using two rovers, the team set out 1,180 overhead line mast locations in approximately two weeks. A conventional total station approach would have taken at least twice as long.
During and After Construction
Surveying remains critical throughout active construction. A large share of the work involves setting out planned construction activities, especially civil engineering work in areas where precise survey data is critical.
Another major task is documenting completed work for the client. This includes design versus as-built comparisons and, where necessary, documentation that supports change orders. The methods used can cover nearly the full range of approved surveying technologies, depending on the site conditions and the level of accuracy required.
Documenting restricted clearance locations is one of the most important tasks during or after construction. Modern surveying technologies can also support construction directly, including logistics and material planning.
Restricted Clearance Surveys
On existing lines, most relevant restricted clearance locations are already known and are included in the information provided by the client. These locations are commonly found around bridges, signals, tunnels, and especially in station areas.
After construction, the affected locations must be measured again to confirm that safe railway operations remain possible. Any new restrictions created by the work must also be added to the final as-built records.
On open track, point specific measurements are often sufficient because potential conflicts can usually be ruled out visually or are limited to short sections. Station areas are different. Infrastructure is much more concentrated, so construction work and final conditions need to be monitored and documented with much greater care.
Measuring Material Volumes
Large construction projects move large amounts of material, and transportation capacity needs to be planned as accurately as possible. This applies to sleepers, rails, ballast, and often significant quantities of earth.
On the Neustadt Glewe to Parchim project, which was carried out in parallel with the Hamburg to Berlin corridor work, extensive construction was planned along the trackside paths and the railway embankment. Site conditions and vegetation had changed enough that the available design data and photographic records no longer provided a reliable basis for estimating earthwork volumes.
LiDAR provided a practical solution. During an existing corridor closure, approximately 16 kilometers of the affected section were walked and scanned from both sides in a single day using the TrueView GO handheld LiDAR scanners. The resulting data made it possible to classify vegetation and other elements that could distort the calculation, then determine the volume of earth that needed to be removed or placed.
With that information, transportation could be planned more accurately and resources could be used more efficiently. The same approach can be used for material stockpiles on staging areas. The TrueView GO 116S scanner can often measure a stockpile faster and more accurately than counting truckloads or relying on simplified geometric assumptions.
The workflow is straightforward. The operator walks around the stockpile with the scanner, and the captured data are then processed in software to calculate volume.
Conclusion
The examples in this article are not intended to cover every possible use of construction surveying. They do, however, show how well-planned surveying services can support major projects when teams have the right technology and enough time to use it effectively.
New technologies continue to expand what’s possible. They allow teams to collect more data, target that data more precisely, and complete the work in less time. They can also reduce disruption to railway operations by limiting the need for track closures and improve safety by keeping personnel out of difficult or hazardous areas.
The key is to recognize surveying as an essential part of project delivery, not simply as a supporting task. The industry also needs to continue attracting young professionals to railway infrastructure surveying. That includes recognizing the value of new technologies and creating approval and certification processes that allow those tools to be used effectively.
Sources
[1] Bauer, F.; Sauer, C.: Reconstruction of the Eifel line after flood damage, EI 03/2023, pp. 44 to 48.
[2] Ramann, J.; Sinning, A.; Wegner, V.: Introduction of Mobile Mapping for Track Surveying, EI 04/2023, pp. 19 to 24.
Author
Guido Kossert
Surveying Engineer
Spitzke SE, Grossbeeren