用测深的雷达制图水下地形

作者：Reka Vasszi

Measuring water depth for nautical purposes dates back to ancient civilisations. As technology has evolved through centuries, besides ship-based echosounding, remote monitoring and mapping of water bodies became more available via LiDAR bathymetric surveys conducted by airborne systems.

Bathymetric surveys allow professionals to measure water depth, map the underwater terrain, classify submerged vegetation and habitat as well as study marine ecology, water-quality, contaminant spills and hydrodynamics.

With the 4X bathymetric product line, Leica Geosystems introduced an innovative high-resolution technology for shallow water and coastal mapping and increased point density by a factor of four compared to previous airborne systems versions. TheLeica Chiroptera 4X，测深和地形激光雷达系统，捕获140,000 points per second并覆盖浅水区25 metre depth。这款高效的沿海调查激光雷达传感器旨在为环境监测，研究和测量提供更准确的数据，即使在浑浊的水中进行了研究和测量表明，其效率映射了加拿大的约翰半岛和太平洋的汤加群岛。

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改善浅水检测

Dr. Tim Webster, research scientist at the Applied Geomatics Research Group (AGRG) from Nova Scotia Community College, was among the first to use the new Chiroptera 4X to survey the coastal zone of Cape John peninsula in Canada.

使用传统的映射浅水和沿海地区itional aerial photography or boat-based echo sounder methods can be costly, time consuming and challenging due to water clarity and unforeseen weather conditions. To overcome these challenges and increase productivity and data accuracy, Webster decided to use the Chiroptera 4X bathymetric and topographic LiDAR in his geomatics research.

地球研究的目的是双重的。首先，团队映射了benthic habitatand the existing aquaculture in the bay, including the mapping of the shellfish infrastructure and the buoys to estimate how much biomass is being grown.

The second goal of the research was todevelop a hydrodynamic model为了帮助新牡蛎农场的租赁，并提议在海湾周围的适当地点，而不会损害敏感的Zostera marinaor so-called eelgrass. The eelgrass beds are important for sediment deposition and nursery grounds for many species of fish and shellfish, thus it is used as an ecosystem health indicator by Fisheries and Oceans Canada (DFO).

Webster has carried out similar research in the region of Maritime Canada in 2014 on how to optimise data collection and post-processing of shallow water topographic-bathymetric LiDAR survey using the Leica Chiroptera II. This time, the professor and his team had the chance to deploy the new Chiroptera 4X and compare the captured data with results from 2014. To量化点云密度和目标识别的改善of the new Chiroptera 4X, the team compared the captured data of three surveying instruments:

• Chiroptera II
• Chiroptera 4x
• Multibeam echo sounder.

This geomatics experiment involved the target surveying of four 1 cubic metre cubes at different water depths to determine the level of detail and data provided by the three different sensors.

研究小组将Chiroptera 4X飞越海湾，收集了有关测量目标的信息，并将2014年从2014年的地形和海床数据与2018年进行的数据进行了比较。研究人员比较了三种不同的调查方法：

• 点云密度
• Orthophoto mosaics
• Digital Elevation Model
• LiDAR amplitude.

The analysis of the captured data was completed using the discrete points derived from the waveform data inLeica LiDAR Survey Studiopost-processing software for point cloud generation and cleaning of raw LiDAR data.

“This particular experiment was to quantify the accuracy and level of detail of the Chiroptera 4X and we are very pleased with the results,”reported Webster.“The results show a significant increase in point density comparing to other equipment, improved target detail, detection limits, and potential for more direct benthic point classification.”

Taking advantage of the Chiroptera 4X’s near-infrared laser for topographic data collection combined with a green laser for bathymetric data collection, the research team precisely captured underwater features and generated virtual reality elevation models to study the benthic habitat. Additionally, researchers proposed sustainable locations for oyster farming without damaging the eelgrass habitat.

“This advancement of Chiroptera 4X is asignificant breakthrough in terms of point densityand it improved the resolution of our coastal zone mapping,”韦伯斯特说。“In any application where target detection is important, I would see the increased benefits of the Chiroptera 4X in industries like hydrography and archaeology.”

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Safe and reliable passage through Pacific waters

太平洋是一个极其文化多样的地区，说明了超过1000种语言的说法，但是，与之联系的是水。长期以来，海洋和沿海海洋一直是太平洋生活方式的组成部分。共享太平洋水域的人的经济，运输和文化是基于海洋提供的海军和海洋基础设施和生态系统。即使海洋导航在群岛中起关键作用，但南太平洋的图表不足。

Shallow water depth range data is critical for safe marine navigation and for construction of harbours, pipelines and any other infrastructure in the coastal area or shallow offshore zones. Without precise information on water depth and the exact location of underwater features and submarine canyons, economic and sustainable development is negatively impacted.

ixblue与Project Partners Geomatics Data Solutions（现为Woolpert，Inc。）和EOMAP澳大利亚被要求绘制汤加群岛及周边地区，以提供3D水深信息并改善该地区的航海图。

The project was part of the Pacific Regional Navigation Initiative (PRNI), an overarching programme geared towards the safe and reliable passage through the Pacific Ocean while protecting the environment and allowing Pacific island economies to develop. The project was sponsored by the New Zealand Ministry of Foreign Affairs and Trade (MFAT) in partnership with the Land Information New Zealand (LINZ).

汤加王国，波利尼西亚群岛，包括169 islands, stretches across approximately800 kilometresin the South Pacific Ocean. In Tonga, agriculture, fishing and forestry provide the majority of employment, therefore, detailed data on both land and shallow water features can support the sustainable development of the island group.

考虑到需要高分辨率调查和图表的相对较大的面积，林茨需要一个智能解决方案，以使预算最大。ixblue与澳大利亚EOMAP和Geomatics数据解决方案一起应用了multi-sensor approach to collect topographic and bathymetric data, including:

• 卫星来源的测深（SDB）
• Airborne Laser Bathymetry (ABL)
• Multibeam Echosounder（MBE）
• Tide gauge install and datum computations.

SDB调查是将大面积映射到可见水深的非常有效的工具，但是capture high-resolution data on land and underwaterthe Chiroptera 4X ALB was used.

The Chiroptera 4X was installed in a Cessna 441 to acquire data for Tonga and Niue, including Beveridge Reef, covering approximately a633-square-kilometre area。Geomatics Data Solutions experts collected both high-resolution bathymetric and topographic data on- and offshore and compared the results of the Chiroptera 4X to SDB.

“有额外的翼手目4 x的密度,有限公司mpared to the Chiroptera II, allows us to run spatial algorithms while reducing the risk that we are accidentally removing seabed objects from the dataset. In other words, it improves our target recognition probability,”said Carol Lockhart of Geomatics Data Solutions.

Beside the bathymetric data of the seafloor, one of the unexpected benefits Geomatics Data Solutions gained from using Chiroptera 4X was the improved penetration of the denser bathymetric laser data on land, providing full coverage even on dense vegetation where the topo laser did not penetrate.

“Local stakeholders will receive full imagery and the topo-bathy dataset, so they can also benefit from the high-resolution data provided with the new Chiroptera 4X, and can use the data for other purposes in addition to improving the nautical charts,”explained Lockhart.

Thecombined approach of different surveying equipmentprovided the complete knowledge of allnavigational-significant features and additional topographic informationof the islands. Thanks to the 4X technology of the newly-released Chiroptera,调查的专家是声音密度的四倍，是以前可能。