Full-waveform LiDAR bathymetry of the La Baule bay

the lidar used is the titan dw 600 from teledyne optech of the “platform topo-bathymétrique aéroportée nantes-rennes”. both 532-nm and 1064-nm lidar swath were acquired 6th and 7th of october 2017, at 400 m above ground with a fov of 28° giving strip image width of 199.5 m with a nominal footprint of 0.49 m along-track and 0.29 m cross-track. a mirror compensation and a sidelap of 30% was used to prevent empty space between strips. the effective incident angle range was from 4 to 20°. the aircraft speed being 201.7 km/h the down track footprint rise up to 0.98 m on sideway what justify a final spatial resolution of 1 m. the laser pulse frequency was set to 50 khz (100 khz locally) giving an overall mean point density of 3.52 points/m². the full-waveform (fwf) was recorded only in 532-nm with a maximum length of 60 m, at 1 ghz frequency, resulting in a vertical resolution of 0.15 m. the optech lidar mapping suite (lms) combines a global positioning system (gps) and inertial measurement unit (imu) to provide a georeferenced point cloud and associated fwf with strip optimization. to compute the complete point cloud, lms uses an analogous approach to photogrammetric block adjustment. on overlap areas between each flight line, planes (typically roofs in land) are extracted and used in a least squares adjustment model provided by lms. the trajectory accuracy provided by geofit company was better than 0.15 m in planimetry and 0.08 m on elevation.the set of data is stored in a zip file composed of the following image files associated with envi headers which are text files describing the image format. labaule_2017106-7-orthophoto: contain the mosaic of rgb image acquired with the camera associated to the lidar. labaule_2017106-7_536nm_raytracing-incident_angles_2m: contains the effective incident angle of each pixel retained in the mosaic with a pixel fov of 0.3° and with a tilling of image strips in the top of each other from the north to the south. labaule_2017106-7_1064nm_raytracing_discrete_echo_ranges_2m: contains the elevation of the water surface of each pixel. labaule_2017106-7_536nm_raytracing_fwf_2m: contains the row fwf projected on the image plane at 0 m ngf with an offset of 30 m for easy spectral processing of the fwf (true range are stored in band names). labaule_2017106-7_536nm_raytracing_fwf_2m_intensity_stats: contains the basic statistics of the fwf intensities. labaule_2017106-7_536nm_raytracing_fwf_2m_range_stats: contains the min, max and thickness of the fwf ranges. labaule_2017106-7_536nm_raytracing_fwf_2m_row_results: contains the row results of water surface and method 1 (dddncfwf echoes) and method 2 (ncfwft-1 bottoms) bathymetries as defined in https://doi.org/10.3390/rs11020117. labaule_2017106-7_536nm_raytracing_fwf_4m_final_bathymetry: contains the final (cleaned ncfwft-1 bottoms) bathymetry.the same data were acquired the 11th of august 2018 during a low tide with the same settings without rgb camera but with a new fwf recorder giving a lot less noisy signal allowing a constant spatial resolution of 1 m. the set of data is stored in a zip file composed of the following image files associated with envi headers which are text files describing the image format. labaule_20180811_536nm_raytracing-incident_angles_1m: contains now 3 channels for the effective incident angle, the strip number and the gps time. labaule_20180811_1064nm_raytracing_discrete_echo_ranges_1m: contains the elevation of the water surface and all echoes above it in each pixel. labaule_20180811_536nm_raytracing_fwf_1m: contains the row fwf projected on the image plane at 0 m ngf with an offset of 30 m for easy spectral processing of the fwf (true range are stored in band names). labaule_20180811_536nm_raytracing_fwf_1m_intensity_stats: contains the basic statistics of the fwf intensities. labaule_20180811_536nm_raytracing_fwf_1m_range_stats: contains the min, max and thickness of the fwf ranges. labaule_20180811_536nm_raytracing_fwf_1m_row_results: contains the row results of water surface and method 1 (dddncfwf echoes) and method 2 (ncfwft-1 bottoms) bathymetries as defined in https://doi.org/10.3390/rs11020117. labaule_20180811_536nm_raytracing_fwf_1m_final_bathymetry: contains the best of dddncfwf echoes and ncfwft-1 bottoms simply presented with the application of a 5x5 median filter.

所采用的激光雷达为来自泰雷徳奥泰克公司的Titan DW 600型号，该型号隶属于“平台拓扑水文航空测量南特-雷恩”。于2017年10月6日和7日，在距地面400米的高度，采用532纳米和1064纳米激光雷达扫描带，以28°的视场角获取了扫描图像，图像条带宽度为199.5米，沿轨名义足迹为0.49米，横轨为0.29米。为避免条带间出现空白区域，采用了镜面补偿和30%的侧向重叠。有效入射角范围为4至20°。飞机速度为201.7公里/小时，在侧向上的下轨足迹上升至0.98米，从而确保了最终的1米空间分辨率。激光脉冲频率设置为50千赫兹（局部为100千赫兹），总体平均点密度为3.52点/平方米。仅在532纳米波长下记录了全波形（FWF），最大长度为60米，频率为1千兆赫兹，从而实现了0.15米的垂直分辨率。Optech激光雷达制图套件（LMS）结合全球定位系统（GPS）和惯性测量单元（IMU），提供带有条带优化的地理参照点云及其相关FWF。为了计算完整的点云，LMS采用了与摄影测量块调整类似的方法。在每条航线之间的重叠区域，提取平面（通常为陆地上的屋顶）并用于LMS提供的最小二乘调整模型中。由GeoFit公司提供的轨迹精度在平面测量中优于0.15米，在高程测量中优于0.08米。数据集以ZIP文件形式存储，包含以下与ENVI头文件相关的图像文件，这些头文件是描述图像格式的文本文件。labaule_2017106-7-orthophoto：包含使用与激光雷达关联的相机获取的RGB图像的镶嵌。labaule_2017106-7-536nm_raytracing-incident_angles_2m：包含镶嵌中每个像素的有效入射角，像素视场角为0.3°，图像条带从北到南相互拼接。labaule_2017106-7-1064nm_raytracing_discrete_echo_ranges_2m：包含每个像素的水面高程。labaule_2017106-7-536nm_raytracing_fwf_2m：包含在0米NGF图像平面上投影的行FWF，偏移量为30米，便于FWF的光谱处理（真实距离存储在波段名称中）。labaule_2017106-7-536nm_raytracing_fwf_2m_intensity_stats：包含FWF强度的基本统计信息。labaule_2017106-7-536nm_raytracing_fwf_2m_range_stats：包含FWF范围的最小值、最大值和厚度。labaule_2017106-7-536nm_raytracing_fwf_2m_row_results：包含水面和方法1（dddncfwf回波）以及方法2（ncfwft-1底部）测深的结果，如https://doi.org/10.3390/rs11020117中所述。labaule_2017106-7-536nm_raytracing_fwf_2m_final_bathymetry：包含经过清理的ncfwft-1底部的最终（清洁）测深。相同的数据于2018年8月11日低潮期间，使用相同的设置获取，但没有RGB相机，但配备了新的FWF记录器，信号噪声更低，允许实现恒定的1米空间分辨率。数据集以ZIP文件形式存储，包含以下与ENVI头文件相关的图像文件。labaule_20180811_536nm_raytracing-incident_angles_1m：现在包含3个通道，用于有效入射角、条带编号和GPS时间。labaule_20180811_1064nm_raytracing_discrete_echo_ranges_1m：包含每个像素的水面高程及其上方所有回波。labaule_20180811_536nm_raytracing_fwf_1m：包含在0米NGF图像平面上投影的行FWF，偏移量为30米，便于FWF的光谱处理（真实距离存储在波段名称中）。labaule_20180811_536nm_raytracing_fwf_1m_intensity_stats：包含FWF强度的基本统计信息。labaule_20180811_536nm_raytracing_fwf_1m_range_stats：包含FWF范围的最小值、最大值和厚度。labaule_20180811_536nm_raytracing_fwf_1m_row_results：包含水面和方法1（dddncfwf回波）以及方法2（ncfwft-1底部）测深的结果，如https://doi.org/10.3390/rs11020117中所述。labaule_20180811_536nm_raytracing_fwf_1m_final_bathymetry：通过应用5x5中值滤波器，将dddncfwf回波和ncfwft-1底部最佳地呈现出来。