How Cheap Drones Helped Create Maps After the Nepal Quake
Following a series of severe earthquakes in 2015, many communities in Nepal struggled to rebuild their homes and lives. Aerial imagery can be helpful when planning post-disaster recovery activities, however people on the ground found that the quality of available satellite imagery was too low to be useful, especially given how densely built up Kathmandu and other cities in Nepal are.
One of the local organisations that was looking into this issue was Kathmandu Living Labs. They were interested in getting frequently updated imagery at a higher spatial resolution without being dependent on an external company that may or may not provide the satellite imagery at a discount. At the same time, Kathmandu University has been experimenting with the use of drones for agricultural purposes and other tasks such as mapping of landslides.
A pilot project led by the humanitarian UAV network UAViators, in collaboration with Kathmandu University and Kathmandu Living Labs, looked at how comparatively affordable consumer drones could be used to achieve similar results to those of more expensive professional mapping drone. The target area was the village of Panga, which had been severely damaged by the earthquake.
UAViators had formed a partnership with drone manufacturer DJI and mapping software company Pix4D. These donated Phantom 3 Advanced multi-copter drones, software and staff time to conduct training sessions in Kathmandu. The drones were used together with Android phones running the mobile app Pix4Dcapture, that can be used to create a flight plan. Mapping the area took 1.5 days of flying six drones for a resolution of 3.4 cm. The imagery was processed by Pix4D staff on laptops.
Kathmandu University and the local Community Disaster Management Committee (CDMC) filed a joint application for flight permits and received the Civil Aviation Authority’s permission within a week. Since then, regulations have significantly tightened and obtaining all necessary permissions may now take a month or more.
The ortho-mosaics were printed on simple roll-up posters that were then given to the CDMC of Panga who invited community members to annotate the map directly with additional relevant features such as the location of debris, safe drinking water and health facilities. “We had displayed that map on the street of Panga for two weeks to show local people and outsiders about present conditions.” Later it was used to show the location of temporary shelters and what percentage of displaced families lived in which section of town.
According to Patrick Meier, an internationally recognised expert in humanitarian technology, the hard copy maps catalysed conversations between community members on the strategies and priorities vis-à-vis both the recovery efforts and the preparedness activities that were ongoing in the community.
Professional vs Consumer Drones
The drones used in this pilot project are not considered professional mapping drones, but consumer models that are much more affordable than the professional versions. However, using the flight planning app made it possible to acquire imagery that could be used to produce maps of sufficient quality, as the app controls both the flight path and triggers the camera where necessary.
Major issue: short flight time
The project created very high-quality maps that could not have been made via traditional methods such as satellite imagery. Some limitations also emerged, most notably that the multi-copter drones had a limited battery life of only about 20 minutes and were thus not able to map large areas. In total, mapping the area of Panga took 1.5 days of flying and data processing.
Another unforeseen problem was radio wave interference between the device that controls the photo trigger on the ground and the receiver of the drone. As a result, flights needed to be shortened, since the drone had to stay within a short radius of the controlling device on the ground.
Both Kathmandu University and Kathmandu Living Labs will continue to use the drones that had been donated. However, Elizabeth Gilmour at Kathmandu Living Labs also noted that the short range of the drones is a limiting factor. “The big focus (for Kathmandu Living Labs) is on mapping. It is going to be hard to do a lot of mapping with these UAVs because they have a battery life of only 20 minutes.”
Kathmandu University is currently actively using the drones in a number of projects, such as building damage assessments. The university also teaches 3rd year undergraduate Geomantic Engineering students in how to use the software.
- You can download the full case study here.
Drones in Humanitarian Action is partially funded by DG ECHO. The views expressed in this blog post should not be taken, in any way, to reflect the official opinion of the European Union, and the European Commission is not responsible for any use that may be made of the information it contains.