A challenging surveying mission in Jiuzhaigou:Cooperation of Jouav & Sichuan Geological and Mineral Bureau .


Jiuzhaigou, one of the most famous valley scenic in Sichuan Province, suffered a magnitude 7.0 earthquake in August 8, 2017, damaged areas of scenic and caused massive landslides. So far, there’re still quite a lot geological hidden dangers.

‘402’Geology team of Sichuan Geology and Mineral Bureau(GMB)is responsible for the reconstruction of Jiuzaigou scenic area and the investigation of hidden dangers, JOUAV send CW-15 VTOL UAV on mission to assist ‘402’Geology team an aerial surveying of scenic areas that difficult to reach by human power.

Why is this mission so difficult? Because the flying area is located in Nature Reserve where the South is much higher than the north with a large difference in elevation, approximately 2000 meters north rim, middle peak is more than 4000 meters, approximately 4500 maters south rim. Nature Reserve like Jiuzhaigou always has complex geology background and covers dense vegetation.

"There is a height difference of 1300-1400 meters in the survey area. CW-15 has to shuttle between mountains," said Mr. Li, engineer of ‘402’ geology team, “that tested overall performance and battery efficiency of CW-15.

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Route planning

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POS data

Expert of Jouav offers a solution:

When operating in an area with an attitude difference of more than 1000meters, in order to ensure flight safety and effectiveness, the whole flight plan needs to be divided into steps to protect its dynamical system in case decrease system life.

Points needs to pay attention:

First, you must import the planned route into 3D terrain software(such as Google Map) to check whether the route intersects the mountains and to make sure there’re at least 150m space between drone and mountains.(ps. Special region requires field visit to avoid some errors of Google map)

Generally, in areas with large height difference, the requirement for accuracy can be a little lower than that in others. To ensure mapping quality, the resolution of the lowest point should be satisfies first, then, the overlap rate of the highest point should be guaranteed. (Resolution at the top is definitely higher than at the bottom so that to ensure the overlap rate of the top is enough.)

This time CW-15 equipped aerial survey camera finished 57 sq.km working area in 3 sorties, total 270 mins time. In addition, CW-15 took off at 2574m, average flight height was 4740, 80% overlap rate, and 65% overlap rate of side direction.

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Orthophotgraphy

The result combined with orthophotography is the white areas in the red circles exist disaster risks of landslide, which need to be careful in reconstruction.

Staff of ‘402’ geology team said that they found geological hazards which is hard to find by human power, but easy through the data obtained by CW-15 UAV.

Recommendations for flight operation:

1.If the take-off and landing point has long distance from the route points. It’s ok to track the route points manually after the uav has already climbed at a level is higher than the surrounding mountains. Then, let the uav keep climbing while flying to the next point, that will save operation time and improve efficiency.

2.Optimum operation temperature range of battery is 10℃-40℃, therefor, battery needs to being warmed in low temperature and high altitude area. Usually, before take-off, the batteries should be put at a warm car or be heated with warm air to ensure that the batteries are able to discharge during take-off stage. In preparing, to stick a “hot pack”(a sort of warming stuff will spontaneously release heat)on uav to keep warm during flight.