In May 2014, the worst flooding in the Balkans in 120 years caused massive damage and triggered landslides. In Bosnia Herzegovina these landslides and floods brought an additional danger with them: mines and other explosive remnants of war were dislodged and swept into inhabited areas – in some cases mines were moved by as much as 23 kilometres. When the floodwaters subsided and villagers returned to their homes, most were unaware of this imminent danger.
The Belgian Royal Military Academy (RMA) team worked with the Bosnia and Herzegovina Mine Action Centre (BHMAC) to use drone images that would help model the potential locations of some of the many displaced ERWs and mines. These models were then used to narrow down the search radius for demining teams.
As a result of the wars in the early 1990s, Bosnia and Herzegovina has one of the most serious landmine problems in the world. More than 5,000 people were killed or injured by landmines or unexploded munitions between 1992 and 2008. By 2013, landmines and unexploded munitions remained scattered in 28,699 locations across the country. Before the floods, approximately 540,000 citizens (out of a total population of about 4 million) were living near these locations. Given that the displaced mines were likely to have spread over very large areas, ground searches would have taken too long, and the RMA team sought to reduce the search area by carrying out an initial analysis using up-to-date, high-resolution imagery.
Between May and June 2014, the RMA team deployed MD4-1000 Multicopter Microdrones. The microdrone has a flight time of up to 88 minutes (depending on load and battery) and a flight radius of up to 40 kilometres. The RMA team logged a total of 20 flights (both manual and autonomous) from 13 locations in urban and semi-urban areas. The flight times ranged from 25 to 30 minutes and captured 200 to 500 images at a resolution of 2-5 cm on each flight. Flights were rescheduled when wind speeds reached more than 12 metres per second. The team did not map the entire risk area since the size of the suspected hazardous area before the disaster was 1,207 km². The mission experienced one crash – in the middle of a minefield – that required repairs to the drone.
All flights were operated within line of sight and with a maximum altitude of up to 150 metres, as specified in the permits granted with the support of the Ministry of Security of Bosnia and Herzegovina and the National Directorate of Civil Aviation.
The team used the Agisoft Photoscan software to create a 2D ortho-rectified mosaic of the landslide area along with digital surface models (DSMs) and digital elevation models (DEMs). The spatial resolution of these data ranged from 3 cm to 10 cm. The models, which were accurate to within a few centimetres per pixel, enabled the RMA team to estimate the size of the landslide and to position it on cartographic and mine information system database layers. In fact, the RMA team was able to determine the maximum length of the landslide (142 metres), width (55 metres) and the total area covered (6,650 square metres). The mosaics, DSMs, DEMs and 3D models were then shared with the Department of Geodesy at the University of Sarajevo, where statistical models for assessing the impact of flooding on erosion enabled the team to determine whether ground erosion had potentially displaced any of the known mines. Taken together, these approaches allowed RMA and the University of Sarajevo to identify new areas where unexploded mines might now be located and therefore to declare them risk areas.
According to the RMA team, helicopters were not used because minefields are typically small and widely distributed. The largest area surveyed via drone covered about 2.5 km². Using a helicopter to cover such a small area would not have been practical or cost-effective The RMA team did use helicopters in another area to survey 140 kilometres of a riverbank where some 30 landslides had been reported.
According to BHMAC, the rapid mapping results from the drones were crucial to identify the new locations of the many explosive remnants of war displaced by landslides.
A technical operations officer noted that, “The rapid mapping activities and the results we get from the UAV mission are crucial for damage assessment, and for identifying the new locations of the many explosive remnants of war which have been displaced due to the landslides and flood water. In this case we did not risk putting humans in the danger zones.”
The RMA team also pointed out that their lead expert and drone operator happened to be from the region and thus knew the language and culture. This was instrumental to the success of the mission.
Over the next months, Droneblog will feature summaries of case studies that show how drones are already being used in disaster response operations worldwide. The case studies were produced under the leadership of the Swiss Foundation for Mine Action (FSD) and with funding from EU Humanitarian Aid. The goal of this research initiative is to identify use cases in which cases drones can improve the quality or increase the efficiency of humanitarian aid.
You can find more information about this and other case studies on http://drones.fsd.ch/
- How Drones Can Help in Humanitarian Emergencies - December 2, 2016
- How firefighters in the UK are pioneering the use of drones - November 8, 2016
- How Drones Can Help Improve Refugee Camps - October 26, 2016
- The benefits and limits of drones in search and rescue - October 24, 2016
- How Drones are Helping in Haiti - October 18, 2016