2016 USGS Lidar DEM: Tishomingo, MS

These are Digital Elevation Model (DEM) data for the north and south sections for the 2016 Mississippi Lidar QL2 Lidar project. Class 2 (ground) lidar points in conjunction with the hydro breaklines were used to create a hydro-flattened raster DEM.

North AOI (Northeast MS):

2949 individual 1500 m x 1500 m tiles, 1 m grid spacing

Northern AOI counties: Alcorn, Benton, Itawamba, Lee, Lowendes, Marshall, Monroe, Prentiss, Tippah, Tishomingo, and Union, covering approximately 2318 square miles of the 3825 total square mile project area.

The data for counties in the northern AOI were developed based on a horizontal projection/datum of NAD83 (2011) UTM Zone 16, meters and vertical datum of NAVD1988 (Geoid 12B), meters.

In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Quantum Spatial, Inc. established a total of 59 ground control points that were used to calibrate the lidar to known ground locations established throughout the Mississippi project area. One point was removed due to drastic change in the area. An additional 96 independent accuracy checkpoints, 56 in Bare Earth and Urban landcovers (56 NVA points), 40 in Forested, Shrubs, and Tall Weeds categories (40 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data.

Vertical Accuracy = 4.9 cm RMSE

South AOI (Camp Shelby):

1791 individual 5,000-foot x 5,000-foot tiles, 2,5 ft grid spacing

Southern AOI counties: Forrest, Greene, Lamar, and Perry, covering approximately 1507 square miles of the 3825 total square mile project area.

The data for counties in the southern AOI were developed based on a horizontal projection/datum of NAD83 (2011) State Plane Mississippi East Zone, US survey feet and vertical datum of NAVD1988 (Geoid 12B), US survey feet. NOAA OCM converted the elevations from feet to meters.

In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Quantum Spatial, Inc. established a total of 38 ground control points that were used to calibrate the lidar to known ground locations established throughout the Mississippi project area. An additional 78 independent accuracy checkpoints, 43 in Bare Earth and Urban landcovers (43 NVA points), 35 in Forested, Shrubs, and Tall Weeds categories (35 VVA points), were used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data. One point was removed from the NVA calculations due to drastic change in the area.

Vertical Accuray = 4.6 cm RMSE

Dataset Description: The Mississippi 2016 Aerial LiDAR Mapping project called for the planning, acquisition, processing and derivative products of LIDAR data to be collected at an aggregate nominal pulse spacing (NPS) of 0.7 meters. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base LIDAR Specification, Version 1.2. LiDAR data was delivered in RAW flight line swath format. Corresponding 2.5-foot intensity images in GeoTIFF format and 2.5-foot bare-earth DEM files in ERDAS .IMG format were created with the same tile schema. Tiles names follow the US National Grid naming schema. Hydro-flattened breaklines were produced in Esri file geodatabase format. Continuous contours with a 1-foot interval were produced in Esri file geodatabase format.

Ground Conditions: Lidar was collected in winter of 2016, while no snow was on the ground and rivers were at or below normal levels

The NOAA Office for Coastal Management (OCM) received the data for processing of the data to the Data Access Viewer (DAV) and https. In addition to these bare earth Digital Elevation Model (DEM) data, the lidar point data that these DEMs were created from, are also available. These data are available for custom download at the link provided in the URL section of this metadata record. Hydro breaklines are also available. These data are available for download at the link provided in the URL section of this metadata record. Please note that these products have not been reviewed by the NOAA Office for Coastal Management (OCM) and any conclusions drawn from the analysis of this information are not the responsibility of NOAA or OCM.

To acquire detailed surface elevation data for use in conservation planning, design, research, floodplain mapping, dam safety assessments and elevation modeling, etc. Classified LAS files are used to show the manually reviewed bare earth surface. This allows the user to create intensity images, breaklines and raster DEMs. The purpose of these lidar data was to produce high accuracy 3D hydro-flattened digital elevation models (DEMs) with a 1 meter cell size. These raw lidar point cloud data were used to create classified lidar LAS files, intensity images, 3D breaklines, hydro-flattened DEMs, and contours as necessary.

Raster File Type = IMG

Bit Depth/Pixel Type = 32-bit float

Raster Cell Size = 1.0 Meters for Northern AOI, 2.5 ft for Southern AOI

Interpolation or Resampling Technique = Triangulated Irregular Network (TIN), Linear Interpolation, Proprietary

Any conclusions drawn from the analysis of this information are not the responsibility of NOAA, the Office for Coastal Management or its partners

Data is available online for bulk and custom downloads.

None

Users should be aware that temporal changes may have occurred since this data set was collected and some parts of this data may no longer represent actual surface conditions. Users should not use this data for critical applications without a full awareness of its limitations.

The project specifications require that only Non-Vegetated Vertical Accuracy (NVA) be computed for raw lidar point cloud swath files. The required accuracy (ACCz) is: 19.6 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE of 10 cm in the “bare earth” and “urban” land cover classes. The NVA was tested with 56 checkpoints in the North AOI and 42 checkpoints in the South AOI, all located in bare earth and urban (non-vegetated) areas. These check points were not used in the calibration or post processing of the lidar point cloud data. The checkpoints were distributed throughout the project area and were surveyed using GPS techniques.

Elevations from the unclassified lidar surface were measured for the x,y location of each check point. Elevations interpolated from the lidar surface were then compared to the elevation values of the surveyed control points. AccuracyZ has been tested to meet 19.6 cm or better Non-

Vegetated Vertical Accuracy at 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASRPS Guidelines.

Northern AOI NVA is 4.9 cm RMSE; VVA is 15.4 cm RMSE

Southern AOI NVA is 4.6 cm RMSE; VVA is 9.5 cm RMSE

Datasets contain complete coverage of tiles. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data. The raw point cloud is of good quality and data passes Non-Vegetated Vertical Accuracy specifications.

Data covers the entire area specified for this project.