Protecting people and property with bathymetric LiDAR

Author:Renata Barradas Gutiérrez

日本是一个大群岛位于行为ive convergent zone next to deep trenches on the Pacific side and many faults and canyons in the Japan sea. Due to its geography and complex topography, Japan is one of the most exposed countries on Earth to natural hazards, such as sea-level rise, flooding, earthquakes and tsunamis. Population growth, climate change and economic development, furthermore, are threatening people, infrastructure and the ecosystems located at the plains of several rivers and coasts.

尽管它大大暴露于危险，但在2016年世界风险报告中排名为17^Thmost prone disaster risk country, Japan has lowered its vulnerability by adapting long-term preparedness strategies and taking actions to understand its topography and environment.

Aero Asahi Corp（AAC）的使命是使用最新的硬件和软件技术来保护生命和财产免受任何灾难或事件。这家航空和空间信息服务公司意识到，在未来灾难的情况下，需要数据来减轻风险。为了支持灾难管理和预防，维护基础设施和地图属性，AAC使用移动映射，空中照片调查以及LIDAR地形和测深量调查。

On a mission

Rivers in Japan, directly managed by the government, have a total length of approximately 8,800 kilometres and are characterised by a deep V-shaped rinsing from steep forests. The Ministry of Land, Infrastructure, Transport and Tourism (MLIT) manages and monitors the rivers of the Nippon country. To monitor the river bed deformation every 200-metre pitch, MLIT used in the past an echo sounder performing cross-sectional terrain surveys every five years on the major rivers. Toprevent disasters and speed up any recovery efforts, AAC now provides bathymetric and topographic data and maps到MLIT的河流管理局。

AAC使用Leica Chiroptera II测深和地形LIDAR传感器精确，安全地收集数据，该传感器安装在直升机中，仅需几分钟即可覆盖大面积。Chiroptera II的近红外（NIR）波长用于地形和用于测深的数据收集的绿色波长，使团队可以在浅水区和内陆淡水体中绘制和测量深度，例如河流和湖泊以及周围的洪水泛滥。

“我们收集和分析所有精确的数据，以提供准备使用的信息，例如变形，沉积物，横截面，侵蚀和银行高度，用于管理当局。由于Chiroptera II结合了地形和测深痛，因此我们可以无缝地从水到陆地上进行接缝 - 当河流运行时，这特别有用shallow,”said Hiroshi Isobe, deputy chief of airborne operations at AAC.

AAC通过用内部解决方案（一个回声声音“水下检查员”）补充了用Chiroptera II捕获的数据来改进过去使用的方法。该小组对日本政府控制的河流进行了测试。这项合并的调查帮助团队创建了一个无缝致密点云，无论河水的深度，浊度，颜色，温度和pH值如何。

The perks of attaching a LiDAR sensor to a helicopter

Mountains cover 73 per cent of the land of the rising sun. When performing aerial surveys in mountainous terrain, AAC attachesThe Chiroptera II to the back of an AS350-B3 helicopter with a GNSS antenna on the top of the vertical stabiliser to obtain a georeferenced point cloud with higher density。AAC is convinced that the variable airspeed, the flexible base location, the shorter turning time and the very low-altitude that can be flown with a helicopter is preferable than the quieter flight with long range and extended flight time that a fixed wing plane provides.

“Point clouds obtained in slower airspeed are denser. Flying with a helicopter allows us to collect water depth where a swath boat with an echo sounder cannot enter and control the altitude along the Japanese steep terrains,”said Isobe.

多个应用程序

A wide range of deliverables like digital surface andterrain models, classified point clouds, orthophotos, and GIS layers可以使用Chiroptera II的收集数据来创建以开发hydrological models to analyse the water flows, drainage management, flood control and support land planning activities。专家团队使用Leica Lidar调查工作室（LSS）来了解河流的地形并创建准确的风险分析。

AAC提供的定期横截面调查可用于多种应用，包括：

• 洪水映射
• Environmental modelling and monitoring
• Visualise the riverbed deformation ground and underwater
• Deriving flow capacity
• 水位应用的精度控制。

预测不可预测的

To protect populations living near water bodies authorities need to study the topography of a river and its surrounding area to monitor changes and predict the behaviour of a water body under different conditions. Airborne LiDAR bathymetry is an effective method tosurvey even in hazardous areas and turbid waters, creating accurate and precise models of coastal and inland water bodies。

“从空中激光调查获得的详细地形数据用于模拟洪水，并每小时预测洪水的传播方式。分析了仿真结果和基础设施信息图，以提供危机管理的最佳数据，例如疏散路线，疏散避难所和受影响的人口。此外，洪水期间航拍照片的立体匹配用于分析表面流量和流动方向，”concluded Isobe.