Webinar 39
Drone Use in Bridge Inspection

October 2, 2018

Summary of the Federal Highway Administration’s Quarterly Webinar: Applications of Geospatial Technologies in Transportation


The Federal Highway Administration (FHWA) promotes geographic information systems (GIS) as a means to more effectively manage and improve transportation systems. One of the ways that FHWA does this is through its GIS in Transportation program,1 which identifies timely and critical GIS issues and topics in transportation and connects transportation agencies with available resources and best practices. The webinar summarized here is part of a quarterly series, which is organized through the GIS in Transportation program.

Jennifer Wells (jennifer.wells@state.mn.us) and Barritt Lovelace (blovelace@collinsengr.com) presented on work the Minnesota Department of Transportation (MnDOT) has undertaken to implement its Unmanned Aerial Systems (UAS) Program in its bridge inspection operations. Ms. Wells and Mr. Lovelace discussed the three phases of research focused on utilizing drones as a tool for improving the quality of bridge and structure inspections.

A recording of the webinar can be viewed here.

UAS Bridge Inspection Program Development

MnDOT began its UAS Bridge Inspection program to more effectively collect, store, and communicate bridge condition data. Currently, the agency is in Phase 4 of their UAS implementation plan, which involves performing cost-benefit analyses. Some of the challenges that MnDOT has faced since the beginning of the program include privacy concerns by the general public and general compliance with existing UAS regulations and guidelines. The State DOT mitigated public concerns over privacy issues by ensuring proper signage is in place for areas being inspected by drones in addition to traditional outreach efforts when communicating with the public regarding UAS use. MnDOT also ensures it is in compliance with all governing agencies and laws, and endeavors to be as transparent as possible at all times. To the agency’s surprise, feedback has been overwhelmingly positive on the UAS Bridge Inspection program. One of the results of the program and use of drones thus far has been a reduction in the number of traffic lane closures, thereby improving traffic conditions.

Given the success that MnDOT has experienced thus far, MnDOT expects to continue using drones as tools for bridge inspectors. It is not expected, however, that drones will ever replace bridge inspectors entirely as there are inspections that must be done in person. Others, however, do not require hands-on inspections and therefore drones are an ideal candidate for this work. The use of drones in these cases can lead to greater cost efficiency and improved public traffic conditions.

Hardware and Software

The inspection-specific UAS that MnDOT uses is capable of object-sensing and object-avoidance programming, capable of looking upwards with its camera, and flying without a global positioning system (GPS) so it can fly under bridge decks without fear of losing a signal. The sensors are equipped with photo, video, and thermal imaging capabilities, and are able to operate in confined spaces, which was a major limitation in the first phase of UAS implementation at MnDOT. Gaining access into confined areas is highly beneficial to inspectors, who would otherwise need specialized equipment and a significant amount of time to get into those areas. The ground control system that MnDOT uses gives the UAS operator precision control and the ability to geo-locate assets, and also grants MnDOT the ability to make field measurements to scale.


The UAS Program has allowed MnDOT to gather large amounts of data from their assets (including bridges) that they can process to create 3D models. The photos from the UAS are “stitched” together to create the 3D models with fly-apart viewing for the different layers inspected. These models produce a historical record of the bridge’s condition that can be used to compare against future inspections. The image quality is high enough to also perform measurements within the model.

Each model retains the links to individual photographs so users can perform virtual inspections using computer software. Bridge models that are created maintain high-clarity imaging from the “stitching” process. Users can then magnify any part of a bridge model without loss of clarity. A user is able to write notes and attach them to each piece of the 3D model, providing highly accurate recordkeeping (instead of having to write descriptions for problems found during the inspection). This has increased the efficiency of inspectors looking for identified issues. The UAS program has greatly improved the ability of MnDOT to communicate the condition of bridges to their owners.

MnDOT recently began partnering with Intel, utilizing the company’s Insight Platform. The platform is an asset management program that is built upon drone and imagery data that catalogs MnDOT’s projects and assets. Over time, the UAS Program also expanded to include roadway mapping and underwater asset inspection.

Questions & Answers

When the Carver County road was mapped, was the road closed, and were any FAA waivers required?
The road remained opened, as it was a low AADT [average annual daily traffic] road. This is a common issue. MnDOT plans the UAS paths to not go directly over the roads. If any on-road work is required and a car is coming, MnDOT pauses the mission with the drone moved off the road temporarily.

How does this data make it to the rest of your GIS system?
MnDOT is looking at how to integrate the UAS data into the existing system. This is going to be very important going forward. The Intel software will help with this work.

In MO and IN, we have to work with bats and migratory birds that roost/nest under bridges. Have you had to deal with that problem and if so what measures could you use to minimize/avoid disturbance?
MnDOT works with the northern long-eared bat, and developed their own bridge inspection element for them. The bats do not seem to be disturbed by the drones at all.

We are looking at the airworthiness of adding green and orange strobes to our drones.
All of MnDOT’s drones have built-in lighting systems as part of their designs.

What tier and pricing of Pix4D do you use, and how did you create the orthophotographs that you can put the notes on? Some people use Drone2Map in ArcGIS for porting the data.
MnDOT has two perpetual licenses at $8,000 per year. The Intel software allows data to be shared via the cloud.

1 See the FHWA GIS in Transportation website for details: https://gis.fhwa.dot.gov/.

Return to top

Federal Highway Administration | 1200 New Jersey Avenue, SE | Washington, DC 20590 | 202-366-4000