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Beyond Visual Line of Sight (BVLOS) UAV Flights

Published Date

By combining flight beyond visual line of sight (BVLOS) and direct georeferencing (DG), it is now possible to use a UAV to accurately and efficiently map long corridors, such as highways and pipelines.

Unlike in visual line of sight (VLOS) flights, in BVLOS flights the remote pilot does not have to keep the UAV in visual line of sight at all times but does so from a remote pilot station (RPS) instead. To operate safely, BVLOS requires higher operator qualifications and experience than VLOS, as well as additional hardware and software.


Benefits of BVLOS

BVLOS would make most commercial UAV applications more efficient and cost-effective, because it makes it possible to fly a UAV for several miles without relocating the ground crew and equipment, allowing it to collect much more data in fewer deployments. Some applications can only be executed with BVLOS. Therefore, BVLOS represents a huge area of opportunity for the UAV industry.

 

Applications that require BVLOS to be done well and efficiently include:

Commercial Public Sector
  • Corridor mapping
  • Insurance inspections of damage due to hurricanes, flooding, earthquakes, etc.
  • Large-scale precision agriculture
  • Mapping
  • Package delivery
  • Pipeline monitoring & inspections
  • Powerline monitoring & inspections
  • Railroad inspections
  • Wind farm inspections
  • Border patrol
  • Conservation management
  • Firefighting
  • Forestry
  • Mapping
  • Police work
  • Search & rescue
  • Wildlife monitoring

 

Requirements

Around the world, many jurisdictions either do not permit BVLOS at all or only under certain conditions. Currently, in the United States, the Federal Aviation Administration (FAA) is under Congressional mandate to integrate UAV technology into the National Airspace System (NAS) without introducing an unacceptable level of safety risk—which poses many technical, operational, and regulatory challenges. The agency is working on draft regulations to issue rules for BVLOS operations. Meanwhile, it requires a special waiver for BVLOS flights but has rejected so far 99 percent of the more than 1,200 applications it has received. To obtain the waiver, operators must prove that their UAV operations can be conducted without endangering other aircraft or people and property on the ground.

In low-risk environments BVLOS operations can be conducted safely with proper assistive hardware and training that enable the pilot in command (PIC) to take evasive action if necessary. In general, safe BVLOS operations require systems that:

  1. monitor and transmit in real time the trajectory of the UAV and of cooperative aircraft—using GPS, ADS-B, radar, and transmitters
  2. detect and track non-cooperative aircraft
  3. give the pilot visual and audible alerts, including in case of any reduced functionality, such as latency and failure.

Additionally, pilots must:

  1. have enough training and in-field testing
  2. be aware of existing airspace classes, temporary flight restrictions, and no-fly zones
  3. conduct pre-flight checks of hardware and tests of flight operations in the event of an in-flight failure.


Direct Georeferencing

To create a map from an aerial image, the direction in which the camera was pointed at the time it took a photo (its orientation) is as important as its position. DG makes it possible to efficiently geolocate aerial images with respect to a reference coordinate system with an accuracy superior to that of traditional aerial triangulation, RTK, and PPK, and without requiring ground control points (GCP). Unlike PPK, which only provides a position, DG combines data from a GNSS receiver and an inertial measuring unit (IMU) to determine both the position and the orientation of a mapping sensor.

Additionally, PPK only provides the position of the antenna phase center, which then needs to be translated to the sensor origin. If the sensor is installed on a stabilized mount, as is now standard practice, the photogrammetric solution needs to also model the dynamic offsets between the GNSS antenna and sensor origin. By contrast, DG precisely translates the GNSS solution from the antenna phase center to the sensor origin and, if the sensor is mounted on a stabilized mount, it properly measures its position and orientation.

Once all the data is collected from the UAV and combined with data from a correction service, it can be imported into popular software to create highly accurate orthomosaics, point clouds, or other visualizations. This makes it possible, for example, to closely inspect and visualize a highway to find pavement imperfections, road wear and tear, and other potential safety hazards, without disrupting traffic. As a bonus, the process yields highly accurate orthophotos.


German Case Study
In Halle, Germany, above busy highway A33, construction giant Strabag was able to fly a Microdrones mdMapper1000DG equipped with a FLARM collision avoidance module and special transponders that make it visible to German air traffic control’s Unmanned Aircraft Systems Traffic Management (UTM). UTM can locate, monitor, and track UAVs connected over Deutsche Telekom’s mobile network (LTE). The UAV created a point cloud and orthophotos of a 12 kilometer stretch of the highway. For more details, and to see a video, click here.