2010 Coastal Georgia Elevation Project Lidar Data

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

The purpose of this project is to provide professional surveying and mapping services to collect and deliver topographic elevation data derived

from multiple return light detection and ranging (lidar) measurements for areas in southeast / coastal Georgia. These data are intended for use

in coastal management decision making, including applications such as sea level rise and coastal flood mapping.

Lifts were planned to meet project specifications and were flown under cloud-free conditions in order to collect LiDAR points at an average

of 1.0 meter point spacing. This allows the user to create Intensity Images, Break Lines, and fully Classified LiDAR LAS files.

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All flights for the project were accomplished with customized aircraft outfitted with state of the art navigation systems and the latest in LiDAR

sensor technology. The LiDAR sensors used for this project consisted of Leica ALS 50-II's and ALS 60 and Optech Gemini. Each was configured to meet

or exceed the project specifications which included:

1. Multiple Discrete Return, capable of at least 3 returns per pulse with Intensity values for each return.

2. Nominal Pulse Spacing (NPS) no greater than 1 meter with distribution of geometrically usable points expected to be uniform and free from

clustering.

3. Scan Angle (total Field-of-View (FOV)) should not exceed 40 degrees. Quality assurance on collections performed using scan angles wider than 34 degrees

will be particularly rigorous in the edge-of-swath areas.

4. Accuracy, The National Standard for Spatial Data Accuracy (NSSDA) of 95% confidence level, equal to (RMSEZ * 1.96) in a set of errors assumed

to be normally distributed. Fundamental Vertical Accuracy (FVA) of NSSDA RMSEZ = 18cm (NSSDA AccuracyZ 95% = 36 cm) or better; assessment

procedures to comply with FEMA guidelines.

5. Horizontal accuracy of 4 feet RMSE or better. Additionally, the Consolidated Vertical Accuracy (computed using NDEP and ASPRS methodology

in five (5) separate land cover classes (TBD)) shall meet ASPRS Class 1 (or National Map Accuracy Standard) guidelines for the generation

of 2 foot contours (Accuracyz = 36 cm). LiDAR data from different flight lines shall be consistent across flight lines, i.e., there is minimal

vertical offset within the noise level of the LiDAR system between adjacent flightlines. Maximum vertical offset between flightlines should be

no more than 6 cm.

6. Flightline overlap 20% or greater, as required to ensure there are no data gaps between the usable portions of the swaths.

7. Base stations for GPS surveys shall be based on first or second order survey control stations that are part of the National Geodetic Survey's

Spatial Reference System.

8. Collection Area: Defined Project Area, buffered by a minimum of 200*NPS.

9. Tide: +/- 2 hours of low tide.

Brantley and Wayne Counties were flown using an Optech Sensor. Bryan, Bulloch, Charlton, Effingham, Long, McIntosh, and Screven Counties were flown

using a Leica Sensor. Both sensors were used on Camden County.

LAS 1.2 files (ASPRS Classes (1,2,7,9,10,12); Breakline File Geodatabase; 4' ESRI Grid Files, Raw LiDAR Flightlines

All deliverables meet specifications in contract. LAS Files meet ASPRS Classification Standards.

Any conclusions drawn from the analysis of this information are not the responsibility of the Office for Coastal Management

or its partners.

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

None

None. However, users should be aware that temporal changes may have occurred since this data set was collected and that some parts of the data may

no longer represent actual surface conditions. Users should not use the 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 36cm

or less based on an RMSEz of 18cm x 1.96.

; Quantitative Value: 0.196 meters, Test that produced the value:

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.

Deliverables 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.