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OCM Partners, 2023: 2008 USGS/NPS/NASA Experimental Advanced Airborne Research Lidar (EAARL): Assateague Island National Seashore,

Item Identification

Title: 2008 USGS/NPS/NASA Experimental Advanced Airborne Research Lidar (EAARL): Assateague Island National Seashore
Short Name: usgs2008_assateague_m531_metadata
Status: Completed
Publication Date: 2009

This is a bare earth data set that was collected 24-25 March 2008 along the shoreline of the Assateague Island National Seashore in

Maryland and Virginia. The data falls in these counties: Worcester (MD) and Accomack (VA). A footprint of the data coverage may be

viewed at:

ASCII xyz point cloud data were produced from remotely sensed, geographically referenced elevation measurements cooperatively

by the U.S. Geological Survey (USGS), the National Park Service (NPS), and National Aeronautics and Space Administration (NASA).

Elevation measurements were collected over the area using the NASA Experimental Advanced Airborne Research Lidar (EAARL); a pulsed

laser ranging system mounted onboard an aircraft to measure ground elevation, vegetation canopy, and coastal topography. The system

uses high-frequency laser beams directed at the Earth's surface through an opening in the bottom of the aircraft's fuselage.

The laser system records the time difference between emission of the laser beam and the reception of the reflected laser signal in

the aircraft. The plane travels over the target area at approximately 50 meters per second at an elevation of approximately 300 meters.

The EAARL, developed by NASA at Wallops Flight Facility in Virginia, measures ground elevation with a vertical resolution of 15 centimeters.

A sampling rate of 3 kilohertz or higher results in an extremely dense spatial elevation dataset. Over 100 kilometers of coastline can be

easily surveyed within a 3- to 4-hour mission. When subsequent elevation maps for an area are analyzed, they provide a useful tool to

make management decisions regarding land development.

Original contact information:

Contact Name: Amar Nayegandhi

Contact Org: Jacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FL

Title: Computer Scientist

Phone: 727-803-8747 (x3026)



The purpose of this project was to produce a highly detailed and accurate bare-earth digital elevation map of the Assateague

Island National Seashore in Virginia and Maryland for use as a management tool and to make these data available to natural resource

managers and research scientists.



Supplemental Information:

Raw lidar data are not in a format that is generally usable by resource managers and scientists for scientific analysis. Converting

dense lidar elevation data into a readily usable format without loss of essential information requires specialized processing.

The U.S. Geological Survey's Coastal and Marine Geology Program (CMGP) has developed custom software to convert raw lidar data

into a GIS-compatible map product to be provided to GIS specialists, managers, and scientists. The primary tool used in the conversion

process is Airborne Lidar Processing System (ALPS), a multi-tiered processing system developed by a USGS-NASA collaborative project.

Specialized processing algorithms are used to convert raw waveform lidar data acquired by the EAARL to georeferenced spot (x, y, z) returns

for "first surface" and "bare earth" topography. the zero crossing of the second derivative (that is, detection of local maxima) is used

to detect "first surface" topography, while the trailing edge algorithm (that is, the algorithm searches for the location prior to the

last return where direction changes along the trailing edge) is used to detect the range to the last return or "bare earth".

Statistical filtering, known as the Random Consensus Filter (RCF), is used to remove false bottom returns and other outliers from the

EAARL topography data. The filter uses a grid of non-overlapping square cells (buffer) of user-defined size overlaid onto the original

point cloud. The user also defines the vertical tolerance (vertical width) based on the topographic complexity and point sampling

density of the data. The maximum allowable elevation range within a cell is established by this vertical tolerance. An iterative

process searches for the maximum concentration of points within the vertical tolerance, and removes those points outside of the

tolerance (Nayegandhi and others, 2009). These data are then converted to the North American Datum of 1983 and the North American

Vertical Datum of 1988 (using the GEOID03 model).

The development of custom software for creating these data products has been supported by the U.S. Geological Survey CMG Program's

Decision Support for Coastal Parks, Sanctuaries, and Preserves project. Processed data products are used by the U.S. Geological

Survey CMG Program's National Assessments of Coastal Change Hazards project to quantify the vulnerability of shorelines to coastal

change hazards such as severe storms, sea-level rise, and shoreline erosion and retreat.


Theme Keywords

Thesaurus Keyword
ISO 19115 Topic Category

Temporal Keywords

Thesaurus Keyword
None 2008

Stratum Keywords

Thesaurus Keyword
None Bare Earth

Physical Location

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

Data Set Information

Data Set Scope Code: Data Set
Maintenance Frequency: None Planned
Entity Attribute Overview:

The LAS grid is encoded with a 1 meter resolution. The input parameters for the Random Consensus Filter were:

grid cell size (buffer) = 6 meters x 6 meters; vertical tolerance (vertical width) = 50 centimeters.

Entity Attribute Detail Citation:

The variables measured by EAARL are distance between aircraft and GPS satellites (meters), attitude information (roll, pitch,

heading in degrees), scan angle (degrees), second of the epoch (seconds), and 1-nanosecond time-resolved return intensity waveform

(digital counts). Z value is referenced to orthometric elevations derived from National Geodetic Survey Geoid Model, GEOID03.

Distribution Liability:

Although these data have been processed successfully on a computer system at the U.S. Geological Survey,

no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of

distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the

data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name,

trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United

States Government or any agency thereof.

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

its partners.

Data Set Credit: The U.S. Geological Survey, National Park Service, and National Aeronautics and Space Administration request to be acknowledged as originators of this data in future products or derivative research. Acknowledgment of the U.S. Geological Survey, Florida Integrated Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgement as is standard for citation and legal practices for data source is expected by users of this data. Sharing new data layers developed directly from these data would also be appreciated by the U.S. Geological Survey staff.

Support Roles

Data Steward

CC ID: 690711
Date Effective From: 2009
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


CC ID: 690713
Date Effective From: 2009
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202

Metadata Contact

CC ID: 690714
Date Effective From: 2009
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202

Point of Contact

CC ID: 690712
Date Effective From: 2009
Date Effective To:
Contact (Organization): NOAA Office for Coastal Management (NOAA/OCM)
Address: 2234 South Hobson Ave
Charleston, SC 29405-2413
Email Address:
Phone: (843) 740-1202


Currentness Reference: Ground Condition

Extent Group 1

Extent Group 1 / Geographic Area 1

CC ID: 1138686
W° Bound: -75.402363
E° Bound: -75.091363
N° Bound: 38.326138
S° Bound: 37.851138

Extent Group 1 / Time Frame 1

CC ID: 1138684
Time Frame Type: Discrete
Start: 2008-03-24

Extent Group 1 / Time Frame 2

CC ID: 1138685
Time Frame Type: Discrete
Start: 2008-03-25

Spatial Information

Spatial Representation

Representations Used

Vector: Yes

Access Information

Security Class: Unclassified
Security Classification System:


Security Handling Description:


Data Access Procedure:

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

Data Access Constraints:


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


Distribution Information

Distribution 1

CC ID: 743057
Download URL:
File Name: Customized Download

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

Distribution 2

CC ID: 743058
Download URL:
File Name: Bulk Download

Simple download of data files.



CC ID: 743060
URL Type:
Online Resource


CC ID: 743061
URL Type:
Online Resource


CC ID: 743062
Name: Browse Graphic
URL Type:
Browse Graphic
File Resource Format: kmz

This kmz file shows the lidar footprint for the 2008 USGS/NPS/NASA EAARL for Assateague Island National Seashore.

Activity Log

Activity Log 1

CC ID: 690740
Activity Date/Time: 2016-05-23

Date that the source FGDC record was last modified.

Activity Log 2

CC ID: 690739
Activity Date/Time: 2017-11-14

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

Activity Log 3

CC ID: 718710
Activity Date/Time: 2018-02-08

Partial upload of Positional Accuracy fields only.

Activity Log 4

CC ID: 743059
Activity Date/Time: 2018-03-13

Partial upload to move data access links to Distribution Info.

Technical Environment


Microsoft Windows XP Version 5.1 (Build 2600) Service Pack 2; ESRI ArcCatalog

Data Quality


The expected accuracy of the measured variables is as follows: attitude within 0.07 degree, 3-centimeter nominal ranging accuracy,

and vertical elevation accuracy of +/-15 centimeters for the topographic surface. Quality checks are built into the

data-processing software.

Horizontal Positional Accuracy:

Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.

Vertical Positional Accuracy:

Elevations are vertically consistent with the point elevation data, +/-15 centimeters.

Completeness Report:

Several regions of the dataset are labeled as "No Data". These "No Data" areas are a result of the survey not covering a particular

region, optical water depth of greater than 1.5 Secchi disc depths, or the manual removal of lidar processing artifacts.

Conceptual Consistency:



Process Steps

Process Step 1

CC ID: 1138680

The data are collected using a Cessna 310 aircraft. The NASA Experimental Advanced Airborne Research Lidar (EAARL) laser scanner

collects the data using a green (532-nm) raster scanning laser, while a digital camera acquires a visual record of the flight.

The data are stored on hard drives and archived at the U.S. Geological Survey office in St. Petersburg, Florida and the NASA office

at Wallops Flight Facility in Virginia. The navigational data are processed at Wallops Flight Facility. The navigational and raw

data are then downloaded into the Airborne Lidar Processing System (ALPS). Data are converted from units of time to x, y, z points

for elevation. The derived surface data can then be converted into raster data (GeoTIFFs).

Process Date/Time: 2008-09-15 00:00:00

Process Step 2

CC ID: 1138681

Metadata imported into ArcCatalog from XML file.

Process Date/Time: 2008-09-15 00:00:00

Process Step 3

CC ID: 1138682

The NOAA Office for Coastal Management (OCM) received files in LAS format. The files contained LiDAR intensity and elevation measurements.

OCM performed the following processing on the data to make it available within Digital Coast:

1. The data were converted from UTM, Zone 18 coordinates to geographic coordinates.

2. The data were converted from NAVD88 heights to ellipsoid heights using Geoid03.

3. The LAS header fields were sorted by latitude and updated.

Process Date/Time: 2010-02-01 00:00:00

Catalog Details

Catalog Item ID: 50106
GUID: gov.noaa.nmfs.inport:50106
Metadata Record Created By: Anne Ball
Metadata Record Created: 2017-11-15 15:24+0000
Metadata Record Last Modified By: SysAdmin InPortAdmin
Metadata Record Last Modified: 2022-08-09 17:11+0000
Metadata Record Published: 2022-03-16
Owner Org: OCMP
Metadata Publication Status: Published Externally
Do Not Publish?: N
Metadata Last Review Date: 2022-03-16
Metadata Review Frequency: 1 Year
Metadata Next Review Date: 2023-03-16