Nepal: recommendations for small UAVs

As the tragedy in Nepal unfolds, the immediate rescue response has ended and now efforts are shifting to agencies working on the mitigation of the event and dealing with continuing cascade of consequences and hopefully to recovery as well as humanitarian relief.  We have not been asked to participate and cannot self deploy but to those planning to fly small UAVs, I recommend that you look over the range of uses of small UAVs in the past 8 earthquakes in the past blog (and in more detail in Disaster Robotics). Plus:

  • Be aware that the altitude may change the performance of your platform
  • Working in complex terrains such as mountains will impact any preplanned paths. We have found that imagery reconstructions from fixed-wings will do better with a series of flights “stair stepping” along a hill or mountain than trying to cover the entire area at one altitude. Also a flight at one altitude may violate any flight AGL restrictions because to be high enough to fly at the top of the mountain, you’ve almost certainly exceeded the AGL limits for the lowest part of the terrain. We have found that rotorcraft flight plans work better as a set of vertical planes.
  • If you are planning to conduct structural inspection missions, you will most likely need to fly with 3-10m of the structure. Be aware that this creates wind effects and can interfere with GPS and wireless connectivity. Also, our research with civil engineers indicates that no matter how much video or photos we try to take, having a specialist who knows exactly what to look for is critical.
  • Expect engineers and structural specialists to use the raw images. Our studies at Disaster City indicate that orthomosaics do not accurately show straight edges on buildings and have a slight bit of ghosting, regardless if from fixed or rotorcraft.
  • Be aware that the country may have a temporary flight restriction in order to protect manned helicopters working at low altitudes in the area- that applies to anything that flies, there are no hobbyist exemptions. The normal procedure is for ANY aircraft, manned or unmanned, to coordinate with the air traffic control so that the manned helicopters can continue to operate. Regardless, manned systems cannot see small UAVs and thus cannot avoid. Should they see a small UAV operating and are not briefed, they typically have to return to base because of the possibility of a collision. Sending someone to the Air Branch of the incident command can go a long way to making sure ad hoc flights don’t accidentally interrupt other activities.

 

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