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How Can Power Line EMF Help Drones Fly With Greater Safety and Autonomy?

Updated: Jun 8, 2022

Many UAS and electric utility experts we speak with are unclear about how power line electromagnetic fields (EMF) can be used to provide situational awareness for drones (unmanned aerial systems, or UASs). Most who learn about EM/Nav, our EMF sensor payload for drones, tend to have the initial impression that the technology's purpose is to mitigate the effects of electromagnetic interference (EMI). They're not entirely wrong, however, EMI mitigation only scratches the surface when it comes to UAS features enabled by power line EMF.

EMF opens the door to many new flight features that cannot be accomplished with other UAS technologies. These features are most useful in applications such as power line inspections and long-distance operations in general. The graphic below neatly outlines a few initial features from Manifold Robotics' EM/Nav. Below the graphic we'll explain them and how they work.

Examples of UAS operation with power line EMF.

Safety Features

Minimum Approach Distance

EM/Nav sets distance thresholds, which the UAS cannot cross during flight. The first threshold, highlighted in red in the above graphic, is minimum approach distance (MAD). This user-defined inside boundary prevents collisions with infrastructure, and as a result, gives the pilot more confidence to get up close to the assets and collect high quality data.

Containment Boundary

An outside threshold, highlighted in green above, can be set to contain a UAS's area of operation by preventing the UAS from crossing that boundary. The boundary's distance to the power line is defined by the remote pilot in control. When setting this distance, local, federal aviation laws should be considered and may vary depending on geography, application, and drone type.

For example, in up-close power line inspections with a rotary UASs pilots can make erroneous commands if, say, they don't know the direction their drone is facing. In a right-of-way surrounded by trees this margin of error is that much smaller. Therefore a tighter containment boundary comes in handy by preventing the UAS from moving too far away from the power line towards surrounding trees.

Another example is a scouting or monitoring inspection typically done by a fixed-wing UAS. Operating over longer distances and at higher altitudes, GPS-based navigation alone does not suffice for securing the UAS's airspace. Should an error occur to the GPS, there is no way besides an emergency landing to keep the UAS's trajectory contained. With an EMF containment boundary - or as we have referred to it before, an "EMF corridor" - the UAS can maintain trajectory away from surrounding airspace, infrastructure and people. This concept in particular supports the safe deployment of beyond visual line-of-sight (BVLOS) flight.

Crucially, EM/Nav can set its outside boundary parameter to what is legally defined as a Shielded Area (100 ft vertically and laterally relative to critical infrastructure). In their latest report, the Aviation Rulemaking Committee (ARC) recommends giving UASs right of way within a Shielded Area, as the likelihood of encounters with crewed aircraft is minimal. EM/Nav supports such a mode of operation, as it can contain its UAS to the Shielded Area around a power line.

3D graphic of an EMF corridor with rotary UASs.

Partial and Full Automation

Power line EMF provides UASs equipped with EM/Nav a known angle and distance relative to the line. With this data, the pilot can automate the UAS's positioning and heading to various degrees - in semi-automation or full automation.


In a semi-automated flight mode, EM/Nav uses EMF to enable the UAS to track the power line, while the pilot remains in control of the aircraft's movement. Two parts of navigation are automated when power line tracking is activated: the UAS's distance to the power line (position), and the direction it is facing (heading). With these fixed, the pilot can focus on collecting data more effectively as the UAS respects its distance to the infrastructure while simultaneously tracking it.

This poses a major advantage for UAS inspection teams. Their piloting skills and discretion on data collection are still required, but they can reduce time positioning the UAS and its gimbal to take the right image. This, in turn, yields more data collected per battery-flight, and has potential to turn weeks-long projects into a matter of days.

Full Automation

Fully-automated inspection workflows, which rely on UASs to fly with full autonomy (no piloting involved), has created some division in the UAS inspections community. Some experts argue that UAS technology is not capable of doing the job well enough on its own, and that a pilot's finesse and an inspector's expertise are required on-site to do a sufficient job. While this is true, it's worth highlighting the benefits to automating the process:

  • Data consistency across all pylons and inspection locations;

  • More data per battery-flight;

  • Streamlined flight trajectories and workflow.

The detection of EMF offers a break-through opportunity to execute safe, fully-automated inspections without sacrificing human expertise. Comparing the EMF-based workflow to current fully-automated approaches, such as the use of 3D models that represent the power line, we can already acknowledge major advantages in automation using EMF:

  • Less time flight planning;

  • Safer flight through active and reliable detection of power lines through EMF;

  • Gimbal tracking of EMF;

  • Pilot-interactive: more easily toggle into manual or EMF-guided (semi-autonomous) flight modes.

Here's how: in the EMF approach, waypoints are based on calculated distance and angle to a tower instead of being GPS-based. This means that the waypoints for one tower can be applied across all other towers, and that plotting individual waypoints for a whole mission is not necessary. Compared to the 3D mode approach, this saves significant flight planning time for the UAS team, and doesn't require them to conduct UAS flights only to create a model for flight automation.

Final Thoughts

Power line electromagnetic fields (EMF) offer an exciting opportunity for commercial unmanned aerial systems doing power line inspections and long-distance operations. The features we outlined here will significantly improve those operations by increasing safety and autonomy, thereby decreasing the operational risks and costs. What's more exciting is that these features are still considered the baseline for the practical use of EMF for drone navigation. As our developments continue, the relationship between drones and power lines will grow closer, and as a result, unlock the true commercial potential of UASs.

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