Webinar 38
Drone Use at Alabama Department of Transportation

July 31, 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.

John D’Arville (darvillej@dot.state.al.us) presented on work the Alabama Department of Transportation (ALDOT) has undertaken to implement its Unmanned Aerial Systems (UAS) Program. Mr. D’Arville discussed Federal Aviation Administration (FAA) requirements, training, equipment, software, and sample projects from the past year. Building on their existing work, ALDOT is also hosting a Peer Exchange on drone use in October 2018.

A recording of the webinar can be viewed here.

Unmanned Aerial Systems (UAS) Program Development

The UAS Program at ALDOT has been two years in the making. To ALDOT, safety is of the utmost importance so it has ensured it is in compliance with all flight operation regulations under FAA 14 CFR Part 107 and Alabama State laws. ALDOT’s goal is to continue developing their UAS initiatives, such as their basic operator training. The basic operator training is required for all staff in the program, regardless of previous training or experience. ALDOT staff are currently training with a private company, enrGies, which is run by experienced ex-military UAS pilots. Currently, ALDOT utilizes three models of aircraft: DJI Phantom 4, senseFly’s eBee, and albris. These models have a variety of different cameras that serve specific purposes.

ALDOT created a UAS Command Center as a hub of operations in February 2018. Since then, the UAS Program staff has continued to work closely with the Alabama UAS Working Group. This group focuses on State policy alongside the FAA and the Federal Emergency Management Agency (FEMA) Region VI. A long-term goal for the working group is to develop a statewide database of registered UAS pilots that can be contacted and asked for assistance in the event of an emergency.

Data Collection Methods

ALDOT has developed a highly detailed standard operating procedure guide and a “High Speed Virtual Processing Farm” to rapidly process data gathered via the UAS. What once took six days to process now takes a mere three hours with this new method of data processing. The State DOT heavily uses mobile LiDAR in the UAS Program. ALDOT makes use of a variety of cutting-edge UAS software, including Emotion 3, DJI Go App, Pix4Dcapture and Pix4Dmapper, ContextCapture, and Hydra Fusion.

UAS Pre-Flight Procedures

Before each flight, operators complete a survey that details what the aircraft is being used for, and a risk assessment. The UAS team also coordinates with the FAA’s Low Altitude Authorization and Notification Capability (LAANC) System2 which grants authorization for UAS use in airspace that might otherwise be restricted.

UAS Projects

Current and future drone applications include photography, earthwork volume assessment, vegetation awareness/eradication, bridge and structure inspections, and mobile data integration with GIS. ALDOT recently used UAS to perform traffic pattern analysis to improve roadway safety, develop 3D renderings of future land use with digital models of new buildings, and monitor rockslide threats. ALDOT also used UAS to create “3D Reality Meshes” from oblique images of an area gathered from multiple aircraft over multiple flights. This 3D reality mesh creates a three-dimensional rendering of the area that can be magnified to view a specific feature from a variety of angles. Figure 1, below, is a progression of images that show how these reality meshes are created. Each dot in the leftmost panel represents an image taken by a UAS aircraft to create the rendering in the middle panel. The rightmost panel zooms in on one area in the rendering.

ALDOT-created 3D mesh progression displaying three images: aerial image of area overlaid with dots; rendering of that area; and a zoomed area of that rendered image

Figure 1. 3D Reality Mesh Progression (Source: ALDOT Presentation)

Questions & Answers

With the DJI products, how are you handling unlocks of restricted areas from the manufacturer’s geo-zoning lockout?
ALDOT cannot override geo-zoning lockout and does not recommend doing so unless the operator is willing to take responsibility for this process and outcome.

What software is being used to generate the 3D reality meshes?
The two applications being used are Pix4D and ContextCapture, with the latter being the preferred method.

You mentioned that you’re not seeing design-level survey accuracies. What are you getting and what are your tolerances?
This can vary depending on the environment being surveyed. Horizontal measurements can be very accurate, with an upward limit of nine inches in discrepancy. Accuracy for vertical measurements is more difficult to achieve.

How do you restrict access to imagery with visible personally identifiable information?
Personally identifiable information is not retained by the UAS Program team. Law enforcement is consulted to inform them about the drone activity and what the data is being used for. It is recommended that drone operators do their homework, know what clearances they have, and work with all local agencies to inform them of the activity.


The UAS Program has enabled ALDOT to no longer be dependent on aircraft mobilization for certain projects, reduce personnel costs associated with survey crews, process data “in-house,” and greatly improved ALDOT field personnel safety by allowing them to use UAS to view areas instead of putting themselves into dangerous locations to gather data.

1 See the FHWA GIS in Transportation website for details: https://gis.fhwa.dot.gov/.
2 As of this writing, the LAANC program is available in all regions of the United States. For more information, see this website: https://www.faa.gov/uas/programs_partnerships/uas_data_exchange/

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