2016 North Carolina Digital Elevation Model Phase Four Counties at a 3.125 foot Resolution

The Digital Elevation Models (DEM) were generated at a 3.125 foot resolution as rasters, using the ground (Class 2) points and the hydro flattened breaklines as inputs from the project. The DEMs were produced specific to the 2016 Phase Four project area consisting of 20 North Carolina counties. LiDAR data for the project and the validation site was collected by a single aerial vendor on ESP team between February 27, 2016 and April 17, 2016 and between December 9, 2016 and February 21 of 2017 using Geiger-mode Avalanche Photodiode (GmAPD) sensors. The aerial vendor on the ESP team was Harris Corporation (Harris).Two GmAPD (Geiger-mode) sensors (serial numbers 002 and 003) were used for the data collection of LiDAR data at a 0.35 meter nominal post spacing (NPS). The following counties or portions of counties were collected in the February through April, 2016 mobilization: Alleghany, Stokes, Surry, Cleveland, Gaston, Mecklenburg, Cabarrus, Stanly, Union, and Anson. The following counties or portions of counties we collected in the December, 2016 through February, 2017 mobilization: Cleveland, Gaston, Mecklenburg, Cabarrus, Stanly, Wilkes, Yadkin, Forsyth, Alexander, Catawba, Iredell, Davie, Rowan, and Davidson. All data was collected during leaf-off conditions. Ground survey support for the project included the establishment of GPS base stations and the collection of control points used for calibration. All data was delivered in the North Carolina State Plane Coordinate System, with a horizontal datum of NAD83 (2011), vertical datum of NAVD88 (Geoid 12B), in US Survey Feet. Data was delivered tiled to a 2,500 foot by 2,500 foot tiling scheme unless otherwise specified in this product description. All LiDAR was delivered in LASer (LAS) version 1.4 standard format. Products for this project derived from the source LiDAR included: intensity images in GeoTIFF format, hydro-flattening breaklines in ESRI File Geodatabase format, Digital Elevation Models (DEMs) in TIF format, ESRI Terrain Datasets (by county) in ESRI File Geodatabase format, product and project-level metadata, and project reports to include the Report of Survey, Post-Acquisition Report, and Project Report. All LiDAR and derivative products for this project met the specifications stipulated in Delivery Order 22, the NC LiDAR Standard, and the USGS minimum standards for QL1 LiDAR data. This project was a joint effort between NC Emergency Management, NC Geodetic Survey, and the NCDOT. The following people served as the main representatives for each stakeholder: NC Emergency Management- Hope Morgan (primary contact) and John Dorman; NC Geodetic Survey- Gary Thompson and Watson Ross; NCDOT- Keith Johnston and Marc Swartz, and the United States Geological Survey (USGS.

The purpose of this project was to update existing LiDAR data, originally collected between 2000 and 2005, with more accurate and clearly defined LiDAR data utilizing the latest in sensor technology. Although created for the North Carolina Floodplain Mapping Program for specific use in the engineering aspects of floodplain delineation, the data were also developed to address the elevation data requirements of the broader geospatial community. The North Carolina Floodplain Mapping Program was established in response to the extensive damage caused by Hurrican Floyd in 1999.

NCEM GTM Contract No. 286-000030 ESP CONTRACTOR: ESP Associates. All DEM processing was completed by the prime contractor. Raster File Type = GeoTIFF; 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 or 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.

MicroStation Connect Version 10; TerraScan Version 17; ESRI ArcGIS 10.4.1, Windows 7 Operating System, ESP Analyst, ESP Utilities

The project specifications require that only Non-Vegetated Vertical Accuracy (NVA) be computed for the source, raw lidar point cloud files. The required accuracy (ACCz) is: 18.13 cm at a 95% confidence level, derived according to NSSDA, i.e., based on RMSE (z) of 9.25 cm in the “bare earth” and "urban" land cover classes. The NVA was tested with 444 checkpoints 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. See survey report for additional survey methodologies. 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.Qualitative value:0.142, Test that produced the value: Tested 0.142 meters NVA at a 95% confidence level using RMSE(z) x 1.9600 as defined by the National Standards for Spatial Data Accuracy (NSSDA). The NVA of the source raw lidar point cloud swath files was calculated against TINs derived from the final calibrated and controlled swath data using 444 independent checkpoints located in Bare Earth and Urban land cover classes.

The DEM dataset contains a complete coverage of project tiles. A visual qualitative assessment was performed to ensure data completeness. No void areas or missing data exist.

All data covers the project area, tile to tile with no gaps or no data areas