How Drones Slashed First High-Speed Rail's Surveying Costs

Drones were used to map a 42-mile section of the nation's first high-speed rail project in an active, urbanized transit corridor. Use of UAVs in place of traditional surveying brought down project costs and timelines.

Editor's Note: The California High-Speed Rail Authority aims to connect the San Francisco and Los Angeles mega regions bringing travelers 800 miles in under three hours -- by 2029. Jacobs/Zephyr UAS used drones to complete aerial mapping for a densely populated 42-mile section, with both passenger and freight right-of-way, in just eight weeks. Use of unmanned aerial vehicles (UAVs) reduced traditional surveying costs by 86 percent, and decreased the timeline for surveying significantly. In addition to using senseFly eBee drones, the engineering team also used various Bentley software platforms to generate track plans from the aerial data collected under a tight timeline for pre-engineering tasks.

The following summary of the project, a 2017 Bentley 'Be Inspired' award finalist, is reprinted with permission from Bentley Systems and Jacobs/Zephyr UAS. 

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The California High Speed Rail Authority is planning the first high-speed rail system in the United States. When complete passengers will be able to travel from San Francisco to Los Angeles in under three hours at speeds greater than 200 miles per hour. Jacobs/Zephyr UAS is responsible for developing preliminary engineering design plans to support environmental assessment of the potential impact of the USD 3 billion project on the surrounding infrastructure. The team faced numerous challenges, including a tight schedule, collecting data in the active corridor and constant traffic interruptions.


The engineering team used unmanned aerial vehicles to obtain aerial mapping of the rail corridor, enabling the California High Speed Rail Authority to determine right-of-way impacts with improved accuracy while reducing the environmental footprint of the project. This created an extremely rich color ortho aerial at 1-inch per pixel resolution supporting 1-foot contours and actual, observed accuracy of better than 2 inches for digital terrain models. Once the mapping was complete, the team prepared base maps for the track plan and profiles using Bentley’s MicroStation and Power Rail Track, storing all data in ProjectWise for real-time collaboration.


Combining the use of UAVs with Bentley technology allowed for complete aerial mapping delivery in just eight weeks, as opposed to 18 weeks using conventional manned aerial vehicles, for a 56 percent reduction in delivery time. The aerial mapping cost was originally quoted at USD 550,000, but Bentley’s software reduced these costs by 86 percent. Additionally, utilizing UAVs and Bentley applications increased aerial image quality by four times.

Ours is a project for the 21st century employing 21st century technology, so we want to make sure that we do everything better, faster, and more economically," said Michelle Boehm, California High-Speed Rail Authority's southern California director.

Jacobs/Zephyr prepared base maps for the track plans from the aerial mapping data obtained from the UAVs with MicroStation and Power Rail Track. The geographically dispersed project team used ProjectWise to facilitate efficient file sharing, distribution and version control. The interoperability of Bentley applications was crucial to meeting the aggressive project deadline.

Learn more about the urban obstacles the Jacobs/Zephyr UAS team overcame to obtain high-quality aerial imagery on GIM International.

Watch a presentation on the process that resulted in the selection of drones for surveying this piece of the country's first high-speed rail project:

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