High-Resolution Concurrent Bathymetric and Topographic Surveys of Lake Pushmataha, Choctaw Indian Reservation, East-Central Mississippi, December 2024

In December 2024, the Lower Mississippi-Gulf Water Science Center (LMGWSC) conducted comprehensive field surveys of Lake Pushmataha, a central Mississippi reservoir owned by the Mississippi Band of Choctaw Indians (MBCI) and named in honor of Chief Pushmataha. These surveys aimed to provide high-resolution spatial data to support the Bureau of Indian Affairs (BIA) in designing and implementing safety rehabilitation measures for Lake Pushmataha Dam. Bathymetric data collection took place from December 9 to 12 using a high-resolution multibeam mapping system (MBMS), which included a multibeam echosounder (MBES) and an inertial navigation system (INS) mounted on a 21-foot marine survey vessel following methodologies outlined by Huizinga (2018). To capture shallow areas inaccessible to the MBMS vessel, a single beam echosounder (SBES) and an INS were mounted on a Jon boat and used for additional mapping on December 13. Topographic data covering land elevations and positions within approximately 0.25 miles of Lake Pushmataha's shoreline were collected on December 10 and 11 using an unmanned aircraft system (UAS) equipped with a light detection and ranging (lidar) scanner. This portion of the survey was conducted by Phoenix Unmanned LLC, a specialized provider of remotely piloted aircraft with advanced remote sensing capabilities. The processed multibeam, single beam, and lidar datasets were merged and saved in compressed LASer file format (.laz) as three-dimensional (3D) point geometries in units of US survey feet, with classification codes following the American Society for Photogrammetry and Remote Sensing (ASPRS) lidar point standard (ASPRS, 2011; ASPRS, 2013). The merged dataset is provided with this data release projected in the Mississippi East State Plane coordinate system, with horizontal reference to the North American Datum of 1983 (NAD83, 2011 realization) and vertical reference to the North American Vertical Datum of 1988 (NAVD88). To facilitate evaluations of lake and dam morphology, points classified with code 2 (ground) and code 40 (bathymetric point) were extracted from the provided LAZ file to generate a Triangulated Irregular Network (TIN), which was exported in a Computer-Aided Design (CAD)-compatible format as a DXF (Drawing Exchange Format) file and included with this data release at the request of the BIA for their convenience. Additionally, a shapefile containing coverage polygons representing the approximate spatial extent of each survey method (single-beam, multibeam, or lidar) is included to aid in the interpretation and spatial context of the collected data. Summary of files included with this data release: LakePushmataha_pointcloud.laz: A dataset containing processed multibeam, single beam, and lidar data that have been merged into a single 3D point geometry dataset in compressed LASer file format, suitable for various applications in geographic information systems (GIS) and engineering. LakePushmataha_TIN.dxf: A Triangulated Irregular Network (TIN) generated in CloudCompare using the mesh creation tool, based on points classified as ground (code 2) and bathymetric point (code 40) from the topo-bathymetric dataset (LakePushmataha_PointCloud.laz). The point cloud was sub-sampled to a minimum spacing of 2 feet before meshing. Elevation values are stored in the "Z" coordinate of each TIN face vertex and are referenced to NAVD88 in feet. Horizontal vertex coordinates are referenced NAD83 (2011) and projected in feet to the Mississippi State Plane coordinate system. CUBE_uncertainty_270khz.tif: A raster file containing gridded uncertainty values at the 95% confidence interval, measured in feet, from a multibeam echo sounder (MBES) survey. Uncertainty was estimated through the Combined Uncertainty and Bathymetric Estimator (CUBE) method in HYPACK software, utilizing depth data collected at a frequency of 270 kHz, which showed the lowest bias relative to a merged bathymetric surface (see Attribute Accuracy for details). The raster has a grid size of 5 feet and is projected in the Mississippi East State Plane coordinate system. survey_extents.zip: A zipped directory containing an ESRI Shapefile of coverage polygons representing the approximate spatial extent of the respective survey method (single-beam, multibeam, or lidar). PhoenixUnmanned_lidar_processingreport.pdf: A processing report generated by Phoenix Unmanned, LLC that documents lidar performance, calibration, and accuracy tests.

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