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Short Citation:
OCM Partners, 2023: 2015 Lowndes County (GA) Lidar DEM, https://www.fisheries.noaa.gov/inport/item/49425.

Item Identification

Title: 2015 Lowndes County (GA) Lidar DEM
Short Name: ga2015_lowndes_dem_m5155_metadata
Status: Completed
Publication Date: 2015-12
Abstract:

TASK NAME: NOAA OCM Lidar for Lowndes County, GA with the option to Collect Lidar in Cook and Tift Counties, GA

Lidar Data Acquisition and Processing Production Task

NOAA Contract No. EA133C11CQ0010

Woolpert Order No. 05271

CONTRACTOR: Woolpert, Inc.

This data set is comprised of lidar point cloud data, raster DEM, hydrologic 3-d breaklines, flightline vectors, survey control, project tile index, and project data extent. This task order requires lidar data to be acquired over the Lowndes County, GA area of interest (AOI), and will be acquired as part of this task order. The total area of the Lowndes County, GA AOI is approximately 500 square miles. The lidar data acquisition parameters for this mission are detailed in the lidar processing report for this task order. The lidar data will be acquired and processed under the requirements identified in this task order. Lidar data is a remotely sensed high resolution elevation data collected by an airborne platform. The lidar sensor uses a combination of laser range finding, GPS positioning, and inertial measurement technologies. The lidar systems collect data point clouds that are used to produce highly detailed Digital Elevation Models (DEMs) of the earth's terrain, man-made structures, and vegetation. The task required the LiDAR data to be collected at a nominal pulse spacing (NPS) of 0.7 meters. The final products include classified LAS, four (4) foot pixel raster DEMs of the bare-earth surface ESRI Grid Format. Each LAS file contains lidar point information, which has been calibrated, controlled, and classified. Additional deliverables include hydrologic breakline data, flightline vectors, control data, tile index, lidar processing and survey reports in PDF format, FGDC metadata files for each data deliverable in .xml format. Ground conditions: Water at normal levels; no unusual inundation; no snow.

Original contact information:

Contact Org: Woolpert

Phone: (937) 461-5660

Purpose:

The lidar data will be acquired and processed under the requirements identified in this task order. The data produced for this AOI is intended for use in community decision making, including storm water management applications, such as floodplain mapping.

Notes:

12075

Keywords

Theme Keywords

Thesaurus Keyword
UNCONTROLLED
ISO 19115 Topic Category elevation
None DEM
None Elevation
None lidar
None Model
None raster

Spatial Keywords

Thesaurus Keyword
UNCONTROLLED
None Georgia
None Lowndes County

Physical Location

Organization: Office for Coastal Management
City: Charleston
State/Province: SC

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: As Needed
Entity Attribute Overview:

Raster

Entity Attribute Detail Citation:

none

Distribution Liability:

Any conclusions drawn from the analysis of this information are not the responsibility of Woolpert, Lowndes County, the NOAA Office for Coastal Management, or its partners.

Support Roles

Data Steward

CC ID: 662048
Date Effective From: 2015-12
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Distributor

CC ID: 662050
Date Effective From: 2015-12
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Metadata Contact

CC ID: 662051
Date Effective From: 2015-12
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Point of Contact

CC ID: 662049
Date Effective From: 2015-12
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address: coastal.info@noaa.gov
Phone: (843) 740-1202
URL: https://coast.noaa.gov

Extents

Currentness Reference: Ground Condition

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 662054
W° Bound: -83.614795
E° Bound: -82.982704
N° Bound: 31.095266
S° Bound: 30.58606

Extent Group 1 / Time Frame 1

CC ID: 662053
Time Frame Type: Range
Start: 2015-03-16
End: 2015-03-27

Spatial Information

Spatial Representation

Representations Used

Vector: Yes

Access Information

Security Class: Unclassified
Data Access Procedure:

This data can be obtained on-line at the following URL:

https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=5155;

Data Access Constraints:

None

Data Use Constraints:

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.

Distribution Information

Distribution 1

CC ID: 720824
Download URL: https://coast.noaa.gov/dataviewer/#/lidar/search/where:ID=5155
Distributor:
File Name: Customized Download
Description:

Create custom data files by choosing data area, product type, map projection, file format, datum, etc.

Distribution 2

CC ID: 720825
Download URL: https://coast.noaa.gov/htdata/raster2/elevation/Lowndes_DEM_2015_5155
Distributor:
File Name: Bulk Download
Description:

Simple download of data files.

URLs

URL 1

CC ID: 720827
URL: https://coast.noaa.gov/dataviewer
URL Type:
Online Resource

URL 2

CC ID: 720828
URL: https://coast.noaa.gov
URL Type:
Online Resource

Activity Log

Activity Log 1

CC ID: 662064
Activity Date/Time: 2016-12-01
Description:

Date that the source FGDC record was last modified.

Activity Log 2

CC ID: 662063
Activity Date/Time: 2017-11-14
Description:

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

Activity Log 3

CC ID: 718290
Activity Date/Time: 2018-02-08
Description:

Partial upload of Positional Accuracy fields only.

Activity Log 4

CC ID: 720826
Activity Date/Time: 2018-02-13
Description:

Partial upload to move data access links to Distribution Info.

Data Quality

Accuracy:

LIDAR full returns were compared with NCGS QA/QC checkpoints using only single and final returns per pulse. A vertical bias was

acquired after airport calibration based on this comparison. For the NC Floodplain Mapping Program, the vertical accuracy for

coastal counties is less than or equal to 20 cm RMSE. For mainland counties, the vertical accuracy of the elevation data is less

than or equal to 25 cm RMSE. More information about the Quality Control reports and a summary of the quality control checks for

each county can be found at http://portal.ncdenr.org/web/lr/geodetic/floodplaininfo.

| Quantitative Value: 20 | Quantitative Test Explanation: Less than or equal to 20 cm RMSE of bare earth LIDAR points compared with independent checkpoints.

Horizontal Positional Accuracy:

Compiled to meet 1.180 feet horizontal accuracy at 95 percent confidence level.; Quantitative Value: 0.359 meters, Test that produced the value: Lidar system specifications are available in the project report

Vertical Positional Accuracy:

LAS data covering the Lowndes County Georgia Lidar Task Order was compared to independent survey control points to determine the FVA of the LAS Swath and of the Bare-Earth DEM. In addition, this LAS data was compared to independent supplemental points from categories: Bare Earth Open Terrain, Urban, Tall Weeds and Crops, Brush Lands and Trees, Forested and Fully Grown, and Swamp. Raw LAS Swath Fundamental Vertical Accuracy (FVA) Tested 0.435 feet fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA, using 0.222 feet (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines. Bare-Earth DEM Fundamental Vertical Accuracy (FVA) Tested 0.384 feet fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using 0.196 feet (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines.; Quantitative Value: 0.058 meters, Test that produced the value: RMSE 5.8 cm. LAS Swath Fundamental Vertical Accuracy (FVA) Tested 0.376 feet (0.114 m) divided by 1.96000 yields an RMSEz of 5.84 cm. The report states that RMSE is 0.222 ft (0.0676 cm) however these appear to be on "raw" calculations, therefore the 5.84 cm RMSEz is used because it appears to have been calculate post-processing.; Quantitative Value: 0.132 meters, Test that produced the value: Raw LAS Swath Fundamental Vertical Accuracy (FVA) Tested 0.435 feet (0.132 m) fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the TIN using all points.; Quantitative Value: 0.114 meters, Test that produced the value: LAS Swath Fundamental Vertical Accuracy (FVA) Tested 0.376 feet (0.114 m) fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the TIN using ground points.; Quantitative Value: 0.117 meters, Test that produced the value: Bare-Earth DEM Fundamental Vertical Accuracy (FVA) Tested 0.384 feet (0.117 m) fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA, in open terrain using (RMSEz) x 1.96000 as defined by the National Standards for Spatial Data Accuracy (NSSDA); assessed and reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the DEM.; Quantitative Value: 0.120 meters, Test that produced the value: Urban Land Cover Classification Supplemental Vertical Accuracy (SVA) Tested 0.395 feet (0.12 m) supplemental vertical accuracy at the 95th percentile in the Urban supplemental class reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the DEM. Urban Errors larger than 95th percentile include:

Point 3011, Easting 2604211.017, Northing 235783.615, Z-Error 0.406 feet

Point 3019, Easting 2588522.701, Northing 319686.23, Z-Error 0.468 feet

; Quantitative Value: 0.215 meters, Test that produced the value: Tall Weeds and Crops Land Cover Classification Supplemental Vertical Accuracy (SVA) Tested 0.706 feet (0.215 m) supplemental vertical accuracy at the 95th percentile in the Tall Weeds and Crops supplemental class reported using National Digital Elevation Program (NDEP)/ASPRS Guidelines and tested against the DEM. Tall Weeds and Crops Errors larger than 95th percentile include:

Point 4004, Easting 2644432.076, Northing 336352.79, Z-Error 0.720 feet

Point 4

Completeness Report:

The full return mass points contain voids where insufficient energy was reflected from the surface to generate a valid return from

the terrain. Voids in the full return mass points tend to occur in water bodies. Wet sand and certain types of vegetation can also

cause voids or anomalous elevations.

Conceptual Consistency:

Data was vertically adjusted based on RMSE and mean difference from control report.

Lineage

Process Steps

Process Step 1

CC ID: 662038
Description:

Using one Leica Optech Gemini (lidar) system on board a Cessna 310 Titan fixed-wing aircraft, lidar data, at a nominal pulse spacing (NPS) of 0.7 meters, was collected for this task order (approximately 500 square miles). AGL = 6500 feet - Aircraft Speed = 150 Knots, Field of View (Full) = 40 degrees, Pulse Rate = 272.0 kHz, Scan Rate = 41.0 Hz, with an average side lap of 20%. Multiple returns were recorded for each laser pulse along with an intensity value for each return. Five (5) missions were flown between March 16, 2015 and March 27, 2015. One (1) Global Navigation Satellite System (GNSS) Base Station was used in support of the lidar data acquisition. Specific information regarding latitude, longitude, and ellipsoid height to the L1 phase center is included in the lidar processing report. Multiple returns were recorded for each laser pulse along with an intensity value for each return. The lidar data acquisition parameters for this mission are detailed in the lidar processing report for this task order. For all acquired lidar data as part of entire NOAA Lidar for Lowndes County, GA task order, the geoid used to reduce satellite derived elevations to orthometric heights was GEOID12A. Data for the task order is referenced to the StatePlane Zone of Georgia West, North American Datum of 1983 (2011) US Feet, and NAVD88, in US Feet. Once the data acquisition and GPS processing phases are complete, the lidar data was processed immediately to verify the coverage had no voids. The GPS and IMU data was post processed using differential and Kalman filter algorithms to derive a best estimate of trajectory. The quality of the solution was verified to be consistent with the accuracy requirements of the project. The SBET was used to reduce the lidar slant range measurements to a raw reflective surface for each flight line. The coverage was classified to extract a bare earth digital elevation model (DEM) and separate last returns. The Optech Gemini calibration and system performance is verified on a periodic basis using Woolpert's calibration range. The calibration range consists of a large building and runway. The edges of the building and control points along the runway have been located using conventional survey methods. Inertial measurement unit (IMU) misalignment angles and horizontal accuracy are calculated by comparing the position of the building edges between opposing flight lines. The scanner scale factor and vertical accuracy is calculated through comparison of lidar data against control points along the runway. Field calibration is performed on all flight lines to refine the IMU misalignment angles. IMU misalignment angles are calculated from the relative displacement of features within the overlap region of adjacent (and opposing) flight lines. The raw lidar data is reduced using the refined misalignment angles.

Process Date/Time: 2015-03-17 00:00:00

Process Step 2

CC ID: 662039
Description:

Ground control and QAQC control point survey was performed by Woolpert surveyors, to support the NOAA Lidar for Lowndes County, GA project. All surveys were performed in such a way as to achieve ground control that supports lidar data at 9.25 cm RMSE accuracy and satisfy a local network accuracy of 5 cm at a 95% confidence level. All ground control survey field activities took place from 03/16/2015 thru 03/23/2015. Woolpert collected control data for data processing as supplemental QAQC points. The supplemental QAQC points were collected to be used in independent accuracy testing. The field crew utilized Real-Time Kinematic (RTK) GPS surveying throughout most of the ground control data collection process. Using RTK GPS techniques, observations were performed on a total of 30 LiDAR control points and 152 ground control quality check points. 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 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.

Process Date/Time: 2015-03-17 00:00:00

Process Step 3

CC ID: 662040
Description:

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 homogenous coverage throughout the project area. 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), Noise (Class 7), Water (Class 9), Ignored Ground (Class 10), Overlap Default (Class 17) and Overlap Ground (Class 18). 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. Classification of water (class 9) and ignored ground (class 10) was completed via the use of the hydrologic breaklines collected for the hydro-flattening phase. The overlap classes were 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. The returns determined to be overlap are then further classified to produce overlap default (class 17) and overlap ground (class 18). 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. The method used to create the DEM consisted of isolating the ground (class 2) points and introducing 3-d breakline data derived from delineating hydrologic features and applying USGS v1.0 hydro flattening specification z-values. This combined dataset was then processed into a gridded format for additional QAQC to ensure DEM quality. Following QAQC process completion, a gridded raster file was created on a per tile basis. The task order projection information was applied to the final raster dataset. Prior to delivery, all raster files were visually reviewed to ensure coverage and reviewed using automated processes to ensure proper formatting. The resulting deliverables for this task order consist of classified LAS file in LAS 1.2 format, 4 feet pixel size DEM files in ESRI Grid format, and Hydrologic Breakline, Flightline Vector, and Control Point data in ESRI Geodatabase format.

Process Date/Time: 2015-03-17 00:00:00

Process Step 4

CC ID: 662041
Description:

The first delivery of this dataset (August, 2015) to the NOAA Office for Coastal Management arrived via hard-drive device from Woolpert, the contracting the company for this project. An internal review from the CGSC data team at NOAA OCM generated a report with data concerns and alterations required before accepting the data as final. A second delivery arrived in October, 2015 and the dataset was marked as final and accepted for distribution on the Digital Coast. The project files included lidar, breaklines and DEMs. OCM performed the following processing for data storage and Digital Coast provisioning purposes:

1. The delivered DEM rasters were converted from Georgia West State Plane Coordinate System (1002 in feet) to geographic (decimal degrees).

2. The vertical coordiante system was kept the same, NAVD88 in meters.

Process Date/Time: 2016-09-07 00:00:00

Catalog Details

Catalog Item ID: 49425
GUID: gov.noaa.nmfs.inport:49425
Metadata Record Created By: Anne Ball
Metadata Record Created: 2017-11-15 15:13+0000
Metadata Record Last Modified By: SysAdmin InPortAdmin
Metadata Record Last Modified: 2022-08-09 17:11+0000
Metadata Record Published: 2018-02-13
Owner Org: OCMP
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2018-02-13
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2019-02-13