2010 ARC Dekalb County Georgia Lidar

This metadata record describes the DTM comprised of classified aerial lidar elevation points, photogrammetrically compiled breaklines and the derived TIN for Dekalb County, GA

Original contact information:

Contact Name: Stacy Grear

Contact Org: Dekalb County GIS Department

Title: Acting Director

Phone: 404-371-3619

Email: scgrear@dekalbcountyga.gov will change to scgrear@dekalbcountyga.gov on July 1, 2010

The lidar DEM data was collected for the Dekalb County, GA area. All lidar returns were classified using the default classes of Terrascan processing software for Unclassified Points (class 1), Ground points (class 2), Water points (class 9), Overlap points (class 12). The lidar ground points are supplemented with photogrammmetrically compiled breaklines from digital imagery collected during the same project time frame as the lidar. The ground class points, often refered to as "bald earth" are then used as an input to proprietary and publicly available processing software to generate a Triangulated Irregular Network (TIN) model. Classified lidar DEMs and derived TIN models are useful for a variety of applications, such as aiding in contour generation, development of digital surface models, 3D modeling, flood plane mapping, viewshed analysis and the production of orthophotos.

10373

A footprint of this data set may be viewed in Google Earth at:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2527/supplemental/ga2010_dekalbcounty.KMZ

A Lidar Report from the vendor for this data set may be viewed here:

https://noaa-nos-coastal-lidar-pds.s3.amazonaws.com/laz/geoid18/2527/supplemental/ga2010_dekalbcounty_QC_Report.pdf

LiDAR points in LAS 1.2 format

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Any conclusions drawn from the analysis of this information are not the responsibility

of Kucera International, ARC, USGS, NOAA, the Office for Coastal Management or its partners.

This data can be obtained on-line at the following URL: https://coast.noaa.gov/dataviewer

The data set is dynamically generated based on user-specified parameters.

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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and some parts of this data may no longer represent actual surface conditions.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. These data

depict the heights at the time of the survey and are only accurate for that time.

Attribute accuracy is tested in the LiDAR processing stage. After classification of the LiDAR data, the 'bald earth' point class is compared to ground control collected within the project area.

Horizontal positional accuracy for LiDAR is dependent upon the quality of the GPS/INS solution, sensor calibration and ground conditions at the time of data capture. The standard system results for horizontal accuracy are less than 1 meter.; Quantitative Value: 1 meters, Test that produced the value: This value is computed by comparing ground control to an intensity based image derived from the classified LiDAR data and represents the RMSE of residuals on controls within the project area.

Vertical positional accuracy for LiDAR is dependent upon the quality of the GPS/INS solution, sensor calibration and ground conditions at the time of data capture. The vertical accuracy for this project was tested with a resultant RMSE of 0.057 meter (0.188 feet).; Quantitative Value: 0.057 meters, Test that produced the value: This value is computed by comparing ground control elevation to the classified LiDAR ground surface and represents the RMSE of residuals on controls within the project area. Units = meters.

LiDAR data is collected for the project area. Post processing of the simultaneously acquired GPS/INS is performed and applied to the laser returns to output a point cloud in the specified project coordinate system and datums. The point cloud data is then subjected to automated classification routines to assign all points in the point cloud to ground, water, overlap and unclassified point classes. Anomalous laser returns that occur infrequently are removed entirely from the data set. The ground class points are then compared to surveyed ground control to develop an accuracy measure of the laser terrain data.

LiDAR data is collected within the project area, processed and verified against control.