2016 - 2017 USGS Lidar DEM: Mississippi NRCS

Product: These are Digital Elevation Model (DEM) data for Mississippi NRCS FY16 Lidar as part of the required deliverables for Mississippi NRCS FY16 Lidar project. Class 2 (ground) lidar points in conjunction with the hydro breaklines and bridge breaklines were used to create a 1 meter hydro-flattened Raster DEM.

Geographic Extent: AOI is located in Mississippi over Warren, Hinds, Claiborne, Jefferson, Adams, Franklin, Wilkinson, and Amite Counties. The area of interest covers approximately 4,780 square miles. Dataset Description: Mississippi NRCS FY16 Lidar project called for the Planning, Acquisition, processing and derivative products of lidar data to be collected at a nominal pulse spacing (NPS) of 0.70 meter. Project specifications are based on the U.S. Geological Survey National Geospatial Program Base Lidar Specification, Version 1.2. The data was developed based on a horizontal projection/datum of NAD83, Universal Transverse Mercator, meters and vertical datum of NAVD88 (GEOID12B), meters. Lidar data was delivered as flightline-extent unclassified LAS swaths, as processed Classified LAS 1.4 files, formatted to 5303 individual 1,500m x 1,500m tiles in NAD83(2011) UTM Zone 15N, as tiled Intensity Imagery, and as tiled bare earth DEMs; all tiled to the same 1,500m x 1,500m schema. Please note that tiles 15RXQ330320 and 15RXQ405950 do not contain lidar points. The data boundary intersects these tiles and a hydro breakline was digitized based on this boundary. For this reason a hydro-flattened DEM IMG and Intensity Image was generated. There will be no LAS 1.4 for tiles 15RXQ330320 and 15RXQ405950. The DEM IMG/Intensity tiff file count is 5903. The LAS 1.4 count is 5901.

Ground Conditions: Initial collection of lidar data took place January and February of 2016. During this time some significant precipitation events occurred in the region and led to increased water levels in the Mississippi River and surrounding low-lying areas. Due to these high water levels it was determined that data acquisition be postponed until water levels lowered. Approximately 80% of the AOI had been acquired at this point. The remaining 20% was collected in January of 2017. Some water level differences will be observed in the point cloud and DEM data due to the differing collection dates, specifically in the low-lying areas near the Mississippi River. Woolpert has taken great care to limit the amount of temporal differences between the two collection dates. In order to post process the lidar data to meet task order specifications and meet ASPRS vertical accuracy guidelines, Woolpert established a total of 103 ground control points that were used to calibrate the lidar to known ground locations established throughout the project area. Additional independent accuracy checkpoints were collected (120 NVA points and 90 VVA points) and used to assess the vertical accuracy of the data. These checkpoints were not used to calibrate or post process the data. Due to temporal variability, visible artifacts in the project DEM are evident within a historical floodplain along a portion of the Mississippi River. Lidar acquisition occurred when river levels were below action stage per NOAA flood gauge readings, however, some areas within the floodplain exhibited higher water levels during the January 2016 flights than what is observed in the January 2017 flights. This is specifically evident within oxbow streams and lakes found within the floodplain. Visible elevation variability in the DEM is located approximately within a bounding box of -91.36 degrees East Longitude, 31.85 degrees North Latitude; -91.24 West Longitude; 31.74 South Latitude.

The NOAA Office for Coastal Management (OCM) downloaded the MS_NatchezTrace_2016 Digital Elevation Model (DEM) files from this USGS site: ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/OPR/ and processed 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.

Data is used for: Soils Mapping, Wetlands delineation & management, Conservation Programs, 3-D Modeling Analysis, Engineering Design, Easements Planning, Dams, Hydrology & Hydraulics, Floodplain Analysis, Irrigation Systems, Precision Agriculture, Watershed Management, Erosion Control, Ponds, Cultural Resources, Water Resources, Ecology Determinations, and etc.

Raster File Type = IMG Bit Depth/Pixel Type = 32-bit float Raster Cell Size = 1 Meter Interpolation or Resampling Technique = Triangulated Irregular Network Required Vertical Accuracy = 19.6 cm NVA

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.

LAS data covering the Mississippi NRCS FY16 Lidar Task Order were compared to independent survey control points to determine the NVA of the LAS Swath and of the Bare-Earth DEM. In addition, this LAS data were compared to independent VVA points.

LAS Swath Non-Vegetated Vertical Accuracy (NVA) Tested 0.086 Meters Non vegetated vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using 0.044 Meters (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines.

Bare-Earth DEM Non-Vegetated Vertical Accuracy (NVA) Tested 0.090 Meters Non vegetated vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using 0.046 Meters (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported against 120 NVA points using National Digital Elevation Program (NDEP)/ASPRS Guidelines.

Raw Swath Non-Vegetated Vertical Accuracy (NVA) Tested 0.098 Meters Non vegetated vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported against 120 NVA points using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the TIN using all points.

Vegetated Vertical Accuracy (VVA) Tested 0.168 Meters at the 95th percentile reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the DEM using 90 VVA points.

VVA Errors larger than 95th percentile include:

Point 3011, Easting 675825.520, Northing 3459581.594, Z-Error 0.217 Meters

Point 3065, Easting 759685.655, Northing 3563636.079, Z-Error 0.253 Meters

Point 3082, Easting 716803.448, Northing 3586933.044, Z-Error 0.182 Meters

Point 3083, Easting 723720.652, Northing 3592543.530, Z-Error 0.174 Meters

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.