From concept to feasibility in aerial mapping

Starting in 2005, the French Naval Hydrographic and Oceanographic Office (Service Hydrographique et Océanographique de la Marine [SHOM]) and the French National Geographic Institute (Institut Géographique National [IGN]) began conducting, as part of the national project Litto3D®, a series of coastal surveys of the metropolitan France and some overseas territories.

The coastal areas were at that time poorly described; airborne bathymetric LiDAR data were used to create a continuous altimetry dataset of the coastal zone. The purpose of this project was to produce better risk management prevention plans for floods, landslides and earthquakes, and to support economic development strategies, environmental protection policies and scientific studies that require the knowledge of the near shore topography and bathymetry.

从2007年到2015年，SHOM通过将数据获取分包给调查公司，在机载激光雷达测深（ALB）技术领域建立了强大的专业知识。2016年2月，法国环境部正式决定最终确定Litto3D®计划的海事部分；可以直接资助区域ALB调查成本的一半。

This decision opened a new perspective; instead of subcontracting survey companies SHOM could run and operate its own ALB capacity with the guarantee to be financially supported. It was decided to launch a call for proposals on a three-year ALB full service. The selected company would have to provide not only the bathymetric LiDAR system but also the aircraft and its pilots, the training of the laser operators, take care of the maintenances/calibrations, and deal with the administrative support (flight permits, insurance policy, etc.).

Leica Geosystems和Cae Aviation赢得了这种公众招标。

计划映射任务

Leica Geosystems和CAE Aviation动员了他们为SHOM的团队提供全面的理论和实用培训的努力，以了解LIDAR和与此技术相关的软件。

The first survey conducted in Normandy and North France used the Leica HawkEye III, an airborne multi-sensor deep water bathymetric and topographic LiDAR system, mounted on a Cessna Grand Caravan.

During the data acquisition in Cherbourg, theHawkEye IIIcaptured full waveform in a favourable survey environment; the wind conditions were relatively calm with flat seas and without fog in the survey area. In addition, the Leica MissionPro software with the 3D virtual globe view helped in the preparation and planning for the flights, and theLeica FlightProflight management and sensor control system assisted in the collection of the data.

The results of this first topo-bathymetric survey exceeded SHOM’s expectations. The achieved work on morpho-sedimentary cells was impressive. “Leica Geosystems LiDAR technology worked perfectly; no failures occurred during our first mission,” said Yves Pastol, SHOM’s expert on ALB. “Having in our team a Leica Geosystems technician the first weeks of the mission was very instructive. This way SHOM’s crew was able to learn and survey at the same time.”

The challenge

鉴于诺曼底和北法国调查的这些积极发现，Shom决定计划沿着频道海岸线进行重大行动：从Baie du Mont-Saint-Michel（西诺曼底）到比利时边境的海岸调查。第二次Topo-Bandymetric调查将使SHOM能够在2018年中产生完整的地理产品。预期的覆盖范围降至5米，高达400 m内陆。

第二次调查是SHOM的真正挑战。Mont-Saint-Michel以欧洲最高的潮汐而闻名。如果在潮汐时正确定时航班，SHOM团队可以利用它们。恶劣的天气可能是克服的另一个障碍以及英国河道的浑浊沿海水域。再次部署了鹰眼III，以提供高分辨率和准确的深浴，浅浴和地形数据。这种调查中的一个重要目标是在地形和测深数据之间进行平稳的过渡。

“The HawkEye III can achieve earth-sea continuity with its various sensors,” said Pastol. “This technology ensures us there will be no gaps in the Digital Terrain Model (DTM), which is essential for our end product.” On the software side, Leica Geosystems also provides theLeica Lidar调查工作室（Leica LSS）to pre-process the waveform and position data to create classified point clouds. The SHOM team can review the deep bathymetry, the shallow and the topographic LiDAR data at the same time, including reviewing the images taken at the same location as the point cloud data.

“From a cost effective approach, comparing with shipborne surveys in the past, topo and bathy survey had to take place separately and we had to launch a complex merging data process. With Leica Geosystems technology this is not necessary anymore,” said Pastol.

An innovative solution

The LiDAR technology has been widely used in monitoring various natural hazards. Due to the high accuracy of the captured data, the technology is also used in the field of oceanic sciences, including a DTM and bathymetric mapping. The HawkEye III is a simple-to-use sensor optimised for the most demanding survey requirements.

“SHOM has the responsibility to conduct surveys in difficult areas and our partnership with Leica Geosystems gives us peace of mind by dealing with all the other aspects of the project, such as system installation, calibration, technical and aeronautical maintenance, among other tasks,” said Yves-Marie Tanguy, SHOM Litto3D project manager. “SHOM’s needs are vast and complex, but we can testify that Leica Geosystems answers with great professionalism to all our requests.”