Data Management Plan

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.

Process Steps:

• The data were collected using: 1. Two Leica ALS80 HP 1000 kHz Multiple Pulses in Air (MPiA) lidar systems on board WoolpertQSI aircraft. The ALS80 sensor collects up to four returns per pulse, as well as intensity data, for the first three returns. If a fourth return was captured, the system does not record an associated intensity value. 2. One Leica ALS70 500 kHz Multiple Pulses in Air (MPiA) lidar sensors owned and operated by Quantum Spatial. The sensor was mounted in Quantum Spatial aircraft.
• The Lidar data was collected in Twenty-five (25) missions, flown as close together as the weather permitted, to ensure consistent ground conditions across the project area. An initial quality control process was performed immediately on the Lidar data to review the data coverage, airborne GPS data, and trajectory solution. 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 significantly 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.
• LAS Point Classification: The point classification is performed as described below. The point cloud underwent a classification process to determine bare-earth points and non-ground points utilizing "first and only" as well as "last of many" lidar returns. This process determined Default (Class 1), Ground (Class 2), Low Noise (Class 7), Water (Class 9), Ignored ground (Class10), Bridge Decks (Class 17), High Noise (Class 18) classifications. The bare-earth (Class 2 - Ground) lidar points underwent a manual QA/QC step to verify the quality of the DEM as well as a peer-based QC review. This included a review of the DEM surface to remove artifacts and ensure topographic quality. After the bare-earth surface is finalized, it is then used to generate all hydro-breaklines through a semi-automated process. All ground (Class 2) lidar data inside of the Lake Pond and Double Line Drain hydro flattening breaklines were then classified to water (Class 9) using TerraScan/LP360 macro functionality. A buffer of 1.14 feet was also used around each hydro-flattened feature to classify these ground (Class 2) points to Ignored ground (Class 10). All Lake Pond Island and Double Line Drain Island features were checked to ensure that the ground (Class 2) points were reclassified to the correct classification after the automated classification was completed. All overlap data was processed through automated functionality provided by TerraScan to classify the overlapping flight line data to approved classes by USGS. The overlap data was classified using standard LAS overlap bit. These classes were created through automated processes only and were not verified for classification accuracy. Due to software limitations within TerraScan, these classes were used to trip the withheld bit within various software packages. These processes were reviewed and accepted by USGS through numerous conference calls and pilot study areas. All data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. Global Mapper was used as a final check of the bare earth dataset. GeoCue was then used to create the deliverable industry-standard LAS files for both the All Point Cloud Data and the Bare Earth. Woolpert Inc. proprietary software and LP360 was used to perform final statistical analysis of the classes in the LAS files, on a per tile level to verify final classification metrics and full LAS header information.
• 2016-03-15 00:00:00 - Hydro Flattened Raster DEM Process: Class 2 (ground) lidar points in conjunction with the hydro breaklines as well bridge breaklines were used to create a 1 meter hydro-flattened Raster DEM. Using automated scripting routines within ArcMap, an ERDAS Imagine IMG file was created for each tile. Each surface is reviewed using Global Mapper to check for any surface anomalies or incorrect elevations found within the surface.
• 2018-09-18 00:00:00 - The NOAA Office for Coastal Management (OCM) downloaded 5903 MS_NatchezTrace_2016 Digital Elevation Model (DEM) files from this USGS site: ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/OPR/. The data were in UTM Zone 15 North coordinates and NAVD88 (Geoid12B) elevations in meters. The bare earth raster files were at a 1 meter grid spacing. OCM performed the following processing on the data for Digital Coast storage and provisioning purposes: 1. Copied the files to https
• 2024-07-23 00:00:00 - Imagine (*.img) files were converted to cloud optimized geotiffs to better support online access. Vertical georeferencing was also added for NAVD88 meters.

Data is available online for bulk and custom downloads.