Use of High-Resolution Topo-Bathymetry to Assess Shoreline Topography and Future Development of a Slackwater Harbor near Dardanelle, Arkansas, October 2021

The U.S. Army Corps of Engineers - Little Rock District (SWL) Civil Works program has a mission to maintain cohesion between physical and naturally developed environments. Evaluation of shoreline stability and adjacent development of a harbor along the McClellan-Kerr Arkansas River Navigation System at River Mile 202.6 is essential in establishing a baseline for potential impacts and future monitoring of the proposed harbor. A combination of multibeam sonar and high-resolution, low-altitude aerial light detection and ranging (lidar) data were used to provide data and analysis needed for as-built information and future monitoring of river shoreline and floodplain management and maintenance. In October 2021, the U.S. Geological Survey (USGS), in cooperation with the U.S. Army Corps of Engineers, completed high-resolution bathymetric (underwater elevation) and topographic surveys of the Arkansas River and a quarry at the proposed slackwater harbor near Dardanelle, Arkansas. Bathymetric data were collected using a high-resolution multibeam echosounder mapping system (MBMS), which consists of a multibeam echosounder (MBES) and an inertial navigation system (INS) mounted on a marine survey vessel. Data were collected as the vessel traversed the river and quarry along overlapping survey lines distributed throughout the areas. Data collection software integrated and stored the depth data from the MBES and the horizontal and vertical position and attitude data of the vessel from the INS in real time. Data processing required computer software to extract bathymetry data from the raw data files and to summarize and map the information. Topographic data were collected as a lidar point cloud (LPC) using an Unmanned Aircraft System (UAS) with a Yellowscan VX20-100 lidar payload, which consists of the lidar scanner and an INS. The LPC data were collected as the UAS followed two perpendicular transects orientations (north-south and east-west) on separate flights. The LPC was corrected using a post-processed kinematic (PPK) solution with a Trimble R8s base station, and ground control points (GCPs) surveyed using Propeller AeroPoint smart targets which were PPK corrected to a nearby continuously operated reference station (CORS) tower. The LPC was attributed to the American Society for Photogrammetry and Remote Sensing (ASPRS) point classification standards. The LPC was colorized from a UAS-collected red-green-blue (RGB) orthoimage collected using a Ricoh GR camera. The processed bathymetric datasets and the UAS lidar dataset are provided in the ASPRS LAS format with associated metadata files in the zipped archive named SlackwaterHarbor_DardanelleAR_2021-10_data.zip. The LAS format is a standardized binary format for storing 3-dimensional point cloud data and point attributes along with header information and variable length records specific to the data. Data points are stored as a 3-dimensional data cloud as a series of x (longitude), y (latitude) and z (elevation) points. Please refer to http://www.asprs.org/Committee-General/LASer-LAS-File-Format-Exchange-Activities.html for additional information. Topographic data outside of the area collected by the UAS were extracted from aerial lidar data collected in 2014, publicly available from the USGS National Elevation Dataset (NED) at https://prd-tnm.s3.amazonaws.com/LidarExplorer/index.html#/. The two bathymetric datasets, the ground points from the UAS lidar data thinned to a 1.64-foot (0.5-meter) resolution, and the public lidar data were combined to create a multisource point cloud of the ground in the proposed harbor area and surroundings. The multisource point cloud dataset is provided in ESRI Shapefile format (ESRI, 2021) with an attribute table and metadata in the zipped archive named SlackwaterHarbor_DardanelleAR_2021-10_Multisource_data.zip. Attribute/column labels of this table are described in the "Entity and attribute" section of the associated metadata file. The multisource point cloud was used to generate an ESRI ASCII grid (ESRI, 2021) with metadata in the zipped archive named SlackwaterHarbor_DardanelleAR_2021-10_Multisource_grid.zip. References Cited: Environmental Systems Research Institute, 2021, ArcGIS: accessed May 20, 2021, at http://www.esri.com/software/arcgis/.

美国陆军工程兵团小石城分局（SWL）的土木工程项目，其使命在于维持自然物理环境与人工开发环境之间的协调统一。对麦克莱伦-克尔阿肯色河航运系统河段里程202.6处的岸线稳定性及拟建港口邻近开发情况开展评估，是确立潜在影响基线、开展拟建港口未来监测工作的必要前提。本次研究采用多波束声呐与高分辨率低空航空激光探测与测距（light detection and ranging, lidar）数据相结合的方式，为岸线与漫滩管理维护的竣工资料编制及后续监测提供所需的数据与分析支撑。

2021年10月，美国地质调查局（U.S. Geological Survey, USGS）与美国陆军工程兵团合作，完成了阿肯色河及阿肯色州达登内尔附近拟建缓水港区域采石场的高分辨率测深（bathymetric，水下高程）与地形测量。测深数据通过高分辨率多波束测深绘图系统（multibeam echosounder mapping system, MBMS）采集，该系统由安装在海洋测量艇上的多波束测深仪（multibeam echosounder, MBES）与惯性导航系统（inertial navigation system, INS）组成。数据采集过程中，测量艇沿覆盖研究区域的重叠测线航行完成数据收集；数据采集软件可实时集成并存储来自MBES的水深数据，以及来自INS的测量艇水平、垂直位置与姿态数据。

数据处理阶段需借助计算机软件从原始数据文件中提取测深数据，并对信息进行汇总与成图。地形数据则采用搭载Yellowscan VX20-100型激光雷达载荷的无人机系统（Unmanned Aircraft System, UAS）采集为激光雷达点云（lidar point cloud, LPC），该载荷包含激光雷达扫描仪与INS。UAS在两次独立飞行中分别沿南北向与东西向的垂直断面航线飞行，完成LPC数据采集。LPC数据通过后处理运动学（post-processed kinematic, PPK）解算进行校正，校正过程使用Trimble R8s基准站，并采用Propeller AeroPoint智能靶标布设地面控制点（ground control points, GCPs），这些靶标已通过PPK校正至附近的连续运行参考站（continuously operated reference station, CORS）塔楼。LPC数据按照美国摄影测量与遥感学会（American Society for Photogrammetry and Remote Sensing, ASPRS）的点分类标准进行属性标注，其色彩信息源自采用Ricoh GR相机采集的无人机载红绿蓝（red-green-blue, RGB）正射影像。

经过处理的测深数据集与UAS激光雷达数据集以ASPRS LAS格式存储，并附带元数据文件，打包归档至名为SlackwaterHarbor_DardanelleAR_2021-10_data.zip的压缩包中。LAS格式是一种标准化二进制格式，用于存储三维点云数据、点属性，以及对应的数据头信息与可变长度记录。数据点以三维点云形式存储，包含x（经度）、y（纬度）与z（高程）坐标。如需了解更多格式信息，请访问http://www.asprs.org/Committee-General/LASer-LAS-File-Format-Exchange-Activities.html。

UAS采集区域外的地形数据取自2014年采集的航空激光雷达数据，该数据可通过美国地质调查局国家高程数据集（National Elevation Dataset, NED）公开获取，网址为https://prd-tnm.s3.amazonaws.com/LidarExplorer/index.html#/。

研究团队将两组测深数据集、经抽稀至1.64英尺（0.5米）分辨率的UAS激光雷达地面点数据，与公开获取的激光雷达数据进行融合，生成拟建港口区域及周边地面的多源点云。该多源点云数据集以ESRI Shapefile格式（ESRI, 2021）存储，附带属性表与元数据，打包归档至名为SlackwaterHarbor_DardanelleAR_2021-10_Multisource_data.zip的压缩包中。该属性表的列标签详见关联元数据文件的"实体与属性"章节。多源点云被用于生成ESRI ASCII网格（ESRI, 2021），并附带元数据，打包归档至名为SlackwaterHarbor_DardanelleAR_2021-10_Multisource_grid.zip的压缩包中。

参考文献：环境系统研究所（Environmental Systems Research Institute），2021，ArcGIS：2021年5月20日访问，http://www.esri.com/software/arcgis/。