2025 SCDVA Lidar DEM: Charleston County, SC

Create custom data files by choosing data area, map projection, file format, etc. A new metadata will be produced to reflect your request using this record as a base.

Bulk download of data files in the original coordinate system.

The Data Access Viewer (DAV) allows a user to search for and download elevation, imagery, and land cover data for the coastal U.S. and its territories. The data, hosted by the NOAA Office for Coastal Management, can be customized and requested for free download through a checkout interface. An email provides a link to the customized data, while the original data set is available through a link within the viewer.

Link to the Woolpert lidar report.

Link to the breaklines in Esri gdb and OGC GeoPackage formats.

This data source was used to georeference and perform accuracy testing on the lidar point cloud data.

This data source was used to create the classified lidar point cloud data.

This data set was used to create tiled deliverable products.

Ground Control Points: Woolpert utilized 3 Trimble Navigation R12i Model GNSS dual-frequency GPS receivers, and 3 TSC7 data collectors for this project.

The purpose of this survey was to establish three-dimensional coordinates for 31 NVA (non-vegetated vertical accuracy point), 21 VVA (vegetated vertical accuracy point), and 13 LiDAR control points. The points were collected per the flight layout and were uniformly dispersed over the project area.

The field crew utilized Real-Time Kinematic (RTK) GPS surveying throughout the ground control data collection process. Using RTK GPS techniques, observations were performed on a total of 13 LiDAR control points, 31 NVA (non-vegetated vertical accuracy point), 21 VVA (vegetated vertical accuracy point). The survey was conducted using a 1-second epoch rate, in a fixed solution RTK mode, with each observation lasting between 60 to 180 seconds. Each station was occupied twice to insure the necessary horizontal and vertical accuracies were being met for this LiDAR / photogrammetric project.

The “Virtual Reference Station” (VRS) concept is based on having a network (spaced at 50-60kms) of GNSS (GPS or GPS/GLONASS) reference stations permanently connected to the control center via the Internet. The networked stations collectively and precisely, model ionospheric errors for the individual GNSS rover in the network coverage area. The rover interprets and uses the VRS network-correction data as if it is operating with a single physical base station on a very short baseline which increases the RTK performance. Corrections (vectors) are from the closest base, but because the ionospheric error (which is traditionally baseline dependent) is practically negated, the rover's degradation in accuracy due to baseline length starts when the rover is first initialized, that is, at the work site. Thus, accuracies are increased and more consistent throughout the working region

The field crew chief processed all session baselines each day using Trimble Navigation’s Trimble Business Center (TBC) Version 2024.10 baseline processor with the accompanying broadcast ephemeris. Daily processing ensured the integrity of the network as it was constructed and allowed the field crews to immediately reschedule observations of poor baselines.

The spatial reference system for all the AOI’s is South Carolina State Plane. The datum shall be NAD83 (2011) epoch 2010.00 horizontal. Orthometric heights referenced to Geoid 18. Units for both the horizontal and vertical datums will be expressed in International Feet to three (3) decimal places.

Existing NGS published benchmarks were surveyed to assure that there were no discrepancies in the field observation data. Close examinations of the residuals showed no distortions in orientation or scale. The ground control data meets positional accuracies necessary to support 1.0 point per 0.3 meters squared (1’ GSD) data at 95% confidence level as outlined in the Geospatial Positioning Accuracy Standards, Part 3: National Standard for Spatial Data Accuracy (NSSDA), published by the Federal Geographic Data Committee (FGDC-STD-007.3-1998).

Airborne Lidar Data: The lidar data was acquired with a Leica City Mapper Airborne Lidar System (S/N 95519), onboard Woolpert’s aircraft. The Leica City Mapper system, developed by Leica of Herrburgg, Switzerland includes the simultaneous first, intermediate and last pulse data capture module, the extended altitude range module, and the target signal intensity capture module.

Lidar Calibration: The individual flight lines were inspected to ensure the systematic and residual errors have been identified and removed. Then, the flight lines were compared to adjacent flight lines for any mismatches to obtain a homogeneous coverage throughout the project area.

LAS Point Cloud Classification: 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), Overlap Default (Class 12). 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. The overlap class was determined by first identifying the overlapping areas and reclassifying the LAS data by offset from a corridor. This allows the returns located on the edge of the swath to be removed from the bare earth coverage in an effort to produce a more uniform data density.

Vertical Adjustments: The surveyed ground control points are used to make vertical adjustments to the data set and to perform the accuracy checks and statistical analysis of the lidar dataset. Supervisory QC monitoring of work in progress and completed editing ensured consistency of classification character and adherence to project requirements across the entire project area.

Tile Index: A tile index with a tile size of 2,500-feet by 2,500-feet was created in Esri shapefile format.

Deliverable Creation: The resulting deliverables for this task order consist of classified lidar point cloud data in LAS 1.4 format, 2-foot bare-earth digital elevation (DEM) data tiles in ERDAS IMG format, 2-foot digital surface model (DSM) data in raster data tiles in ERDAS IMG format, and 2-foot 8-bit intensity imagery tiles in GeoTIFF format.

The NOAA Office for Coastal Management (OCM) received 4 .img files from the Charleston County Public Works Department. The files were in SC State Plane NAD83(2011) international feet coordinates and the elevations were in NAVD88 (GEOID18) international feet. The bare earth raster files were at a 2 ft grid spacing. OCM assigned the vertical EPSG code (8228) and copied the raster files to AWS S3 for Digital Coast storage and provisioning purposes.