2010 Lidar DEM: Coastal Georgia

Between January and March 2010, lidar data was collected in southeast/coastal Georgia under a multi-agency partnership between the Coastal Georgia Regional Development Center, USGS, FEMA, NOAA and local county governments. Data acquisition is for the full extent of coastal Georgia, approximately 50 miles inland, excluding counties with existing high-resolution lidar derived elevation data. The data capture area consists of an area of approximately 5703 square miles. This project is within the Atlantic Coastal Priority Area as defined by the National Geospatial Program (NGP) and supports homeland security requirements of the National Geospatial-Intelligence Agency (NGA). This project also supports the National Spatial Data Infrastructure (NSDI) and will advance USGS efforts related to The National Map and the National Elevation Dataset.

The data were delivered in LAS format version 1.2 in 5000 x 5000 foot tiles. The data are classified according to ASPRS LAS 1.2 classification scheme:

Class 1 - Unclassified

Class 2 - Bare Earth

Class 7 - Low Point (Noise)

Class 9 - Water

Class 10 - Land below sea level

Class 12 - Overlap

LiDAR collected at 1.0 points per square meter (1.0m GSD) for the entire portion of coastal territory in southeast / coastal Georgia. This area was flown during snow free and leaf-off conditions within two hours of low tide.

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.

Raster DEM files are used to show the Digital Elevation Model of the LAS Class 2 points. Breaklines can be incorporated into the DEM to show a more representative surface .

All deliverables meet specifications in contract.

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 custom and bulk 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 Version 8; TerraScan Version 10; Optech DASHMap 4.1801; TerraModeler Version 10;

GeoCue Version 6.1.21.4; ESRI ArcGIS 9.3.1; Global Mapper Version 11.02; ALS Post Processor 2.70 Build #15; Windows XP Operating System

The project area requires LiDAR to be collected on average of 1.0 meter point spacing or better and vertical accuracy of 18.0 centimeters RMSE or better to support 2' contour generation when combined with breaklines.

Compiled to meet a horizontal accuracy of 1.2 meters (4 ft) RMSE or better.

Compiled to meet National Standards for Spatial Data Accuracy; For this project, vertical accuracy at the 95% confidence interval must be 36 cm or less based on an RMSEz of 18 cm x 1.96.

The vertical accuracy assessment compares the measured survey checkpoint elevations with those of the TIN as generated from the bare-earth LiDAR. The X/Y locations of the survey checkpoints are overlaid on the TIN and the interpolated Z values of the LiDAR are recorded. These interpolated Z values are then compared with the survey checkpoint Z values and this difference represents the amount of error between the measurements. Once all the Z values are recorded, the Root Mean Square Error (RMSEz) is calculated and the vertical accuracy scores are interpolated from the RMSE value. The RMSEz equals the square root of the average of the set of squared differences between the dataset coordinate values and the coordinate values from the survey checkpoints.

Based on the vertical accuracy testing conducted by Dewberry using NSSDA and FEMA methodology, fundamental vertical accuracy (FVA) at the 95% confidence level (called Accuracyz) is computed by the formula RMSEz x 1.9600. The dataset for CGEP satisfies the criteria outlined in project specifications and tested 0.196 m in open terrain, based on RMSEz (0.10 m) x 1.9600 .

Datasets contain complete coverage of tiles.

Bare-earth DEMs were tested by both Photo Science and Fugro EarthData for both vertical and horizontal accuracy. All data are seamless from one tile to the next, no gaps or no data areas.