Topographic Lidar Survey of Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana, July 12-14, 2013 -- Bare Earth Digital Elevation Models (DEMs)

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Frequently anticipated questions:

What does this data set describe?

Title:
Topographic Lidar Survey of Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana, July 12-14, 2013 -- Bare Earth Digital Elevation Models (DEMs)
Abstract:
A topographic lidar survey was conducted on July 12-14, 2013 over Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana. The data were collected at a nominal pulse space of 1 meter (m) and processed to identify bare earth elevations. Bare earth Digital Elevation Models (DEMs) were generated based on these data. Photo Science, Inc., was contracted by the U.S. Geological Survey (USGS) to collect and process the lidar data. The bare earth DEMs are 32-bit floating point ERDAS Imagine (IMG) files with a horizontal spatial resolution of 1-m by 1-m. They are projected to Universal Transverse Mercator (UTM), Zone 16, North American Datum (NAD) 1983, meters (m) coordinates. Their vertical datum is NAVD88 (GEOID12A) meters. Eighty-five DEMs, based on a 2-kilometer (km) by 2-km tiling scheme, cover the entire survey area. These lidar data are available to Federal, State and local governments, emergency-response officials, resource managers, and the general public.
Supplemental_Information:
Lidar data acquisition, calibration, and follow-on processing were completed by Photo Science, Inc. Photo Science was contracted by the U.S. Geological Survey to conduct the work. The geographic extent of each tile falls on even 2000 x and y UTM Zone 16N NAD83 meters. The tile names are assigned according to the U.S. National Grid (USNG) spatial address (http://www.fgdc.gov/usng/how-to-read-usng/index_html). The last 6 digits of the file name are based on the lower-left (LL) xy coordinate of the tile. For example, tile name 16RCU324308 uses 324 to represent an LL x-coordinate of 324,000, and uses 308 to represent an LL y-coordinate of 3,308,000 (ignoring the first digit).
  1. How might this data set be cited?
    U.S. Geological Survey, 2013, Topographic Lidar Survey of Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana, July 12-14, 2013 -- Bare Earth Digital Elevation Models (DEMs): U.S. Geological Survey Data Series 838, U.S. Geological Survey, St. Petersburg, Fla..

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -89.207247
    East_Bounding_Coordinate: -88.030572
    North_Bounding_Coordinate: 30.289239
    South_Bounding_Coordinate: 29.465167
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 12-Jul-2013
    Ending_Date: 14-Jul-2013
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference: Tile Index
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 16
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.9996
      Longitude_of_Central_Meridian: -87.000000
      Latitude_of_Projection_Origin: 0.0
      False_Easting: 500000
      False_Northing: 0.0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest 0.01
      Ordinates (y-coordinates) are specified to the nearest 0.01
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.01
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    Entity_and_Attribute_Overview:
    The bare earth DEMs are composed of single band, 1-m by 1-m resolution, 32-bit floating point continuous rasters in ERDAS Imagine format derived from bare earth classified lidar data. The vertical units are in meters, NAVD88, GEOID12a.
    Entity_and_Attribute_Detail_Citation:
    USGS. 2013. Topographic Lidar Survey of Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana, July 12-14, 2013.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
    Acknowledgment of the U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgment as is standard for citation and legal practices. Sharing of new data layers developed directly from these data would also be appreciated by the U.S. Geological Survey staff. Users should be aware that comparisons with other datasets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in photointerpretation, mapping conventions, and digital processes over time. These data are not legal documents and are not to be used as such.
  3. To whom should users address questions about the data?
    U.S. Geological Survey
    Attn: Nathaniel Plant
    600 4th St. S.
    St. Petersburg, FL
    USA

    727-803-8747 (voice)
    727-803-2031 (FAX)
    nplant@usgs.gov
    Hours_of_Service: Monday through Friday 9:00 AM to 5:00 PM (Eastern Time)

Why was the data set created?

This lidar survey was acquired to document the short- and long-term changes of several barrier island systems. Specifically, this survey supports detailed studies of Chandeleur and Dauphin Islands that resolve annual changes in beaches, berms and dunes associated with processes driven by storms, sea-level rise, and even human restoration activities.

How was the data set created?

  1. From what previous works were the data drawn?
    Raw Lidar Data (source 1 of 2)
    Photo Science, Inc., 20130904, Lidar Raw Data for Gulf of Mexico Barrier Islands: Photo Science, Inc. Aerial LiDAR Department, Photo Science, Inc..

    Type_of_Source_Media: digital hard drive
    Source_Contribution:
    This data source was used to populate the lidar point cloud data.
    Ground Control Points (source 2 of 2)
    U.S. Geological Survey, 2013, Ground Control Points.

    Type_of_Source_Media: online
    Source_Contribution:
    This data source was used in lidar processing and accuracy assessment. This dataset is not included in this Data Series Report.
  2. How were the data generated, processed, and modified?
    Date: 2013 (process 1 of 7)
    Lidar Pre-Processing: Airborne global positioning system (GPS) and inertial measurement units (IMU) data were merged to develop a Single Best Estimate (SBET) of the lidar system trajectory for each lift. Lidar ranging data were initially calibrated using previous best parameters for this instrument and aircraft. Relative calibration was evaluated using advanced plane-matching analysis and parameter corrections were derived. This was repeated iteratively until residual errors between overlapping swaths, across all project lifts, were reduced to acceptable levels. Data were then block adjusted to match surveyed calibration control. Raw data FVA was checked using independently surveyed checkpoints. Swath overage points were identified and tagged within each swath file. The raw lidar data and the ground control points are intermediary datasets and are not included in this Data Series Report. Person who carried out this activity:
    Photo Science, Inc.
    523 Wellington Way
    Lexington, KY
    USA

    859-277-8700 (voice)
    859-277-8901 (FAX)
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Contact_Instructions:
    If unable to reach the contact by telephone, please send an email. You should receive a response within 24 hours.
    Data sources used in this process:
    • Raw Lidar Data
    • Ground Control Points
    Data sources produced in this process:
    • Calibrated Lidar Datasets
    Date: 2013 (process 2 of 7)
    Lidar Post-Processing: The calibrated and controlled lidar swaths were processed using automatic point classification routines in proprietary software. These routines operate against the entire collection—all swaths, all lifts—eliminating character differences between files. Data were then distributed as virtual tiles to experienced lidar analysts for localized automatic classification, manual editing, and peer-based quality control (QC) checks. 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. All classification tags are stored in the original swath files. Person who carried out this activity:
    Photo Science, Inc.
    523 Wellington Way
    Lexington, KY
    USA

    859-277-8700 (voice)
    859-277-8901 (FAX)
    bishop@photoscience.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Contact_Instructions:
    If unable to reach the contact by telephone, please send an email. You should receive a response within 24 hours.
    Data sources used in this process:
    • Calibrated Lidar Datasets
    Data sources produced in this process:
    • Classified Lidar Datasets
    Date: 2013 (process 3 of 7)
    The bare earth surface is then manually reviewed to ensure correct classification on the Class 2 (Ground) points. After the bareearth surface is finalized, it is then used to generate all hydro-breaklines through heads-up digitization. All ground (ASPRS Class 2) lidar data inside of the Lake Pond and Double Line Drain hydro flattening breaklines were then classified to water (ASPRS Class 9) using TerraScan macro functionality. A buffer of 1 m was also used around each hydro flattened feature to classify these ground (ASPRS Class 2) points to Ignored ground (ASPRS Class 10). All Lake Pond Island and Double Line Drain Island features were checked to ensure that the ground (ASPRS Class 2) points were reclassified to the correct classification after the automated classification was completed. All overlap data was processed through automated functionality provided by TerraScan to classify the overlapping flight line data to classes approved by USGS. The overlap data was classified to Class 17 (Overlap Default) and Class 18 (Overlap Ground). These classes were created through automated processes only and were not verified for classification accuracy. Due to software limitations within TerraScan, these classes were used to trip the withheld bit within various software packages. These processes were reviewed and accepted by USGS. All data was manually reviewed and remaining artifacts removed using functionality provided by TerraScan and TerraModeler. Global Mapper was used as a final check of the bare earth dataset. GeoCue was then used to create the deliverable industry-standard LAS files for both the All Point Cloud Data and the Bare Earth datasets. Photo Science proprietary software was used to perform final statistical analysis of the classes in the LAS files, on a per tile level to verify final classification metrics and full LAS header information. Person who carried out this activity:
    Photo Science, Inc.
    523 Wellington Way
    Lexington, KY
    USA

    859-277-8700 (voice)
    859-277-8901 (FAX)
    bishop@photoscience.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Contact_Instructions:
    If unable to reach the contact by telephone, please send an email. You should get a response within 24 hours.
    Data sources used in this process:
    • Classified Lidar Datasets
    Data sources produced in this process:
    • Validated LAS Datasets
    Date: 2013 (process 4 of 7)
    Hydro Classification Breakline Processing: Class 2 lidar was used to create a bare earth surface model. The surface model was then used to heads-up digitize 2D breaklines of inland streams and rivers with a 30-m nominal width and inland ponds and lakes of 8,000 square meters or greater surface area. The breaklines were collected for classification purposes only. The provided breaklines are 2D features and do not contain a valid elevation attribute. All ground (ASPRS Class 2) lidar data inside of the collected inland breaklines were then classified as water (ASPRS Class 9) using TerraScan macro functionality. A buffer of 1 m was used around each breakline feature. These points were moved from ground (ASPRS Class 2) to ignored ground (ASPRS Class 10). The breakline files were then translated to ESRI Shapefile format using ESRI conversion tools. Person who carried out this activity:
    Photo Science, Inc.
    523 Wellington Way
    Lexington, KY
    USA

    859-277-8700 (voice)
    859-277-8901 (FAX)
    bishop@photoscience.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Contact_Instructions:
    If unable to reach the contact by telephone, please send an email. You should receive a response within 24 hours.
    Data sources used in this process:
    • Validated LAS Datasets
    Data sources produced in this process:
    • Hydro Classification Breaklines
    Date: 2013 (process 5 of 7)
    Raster DEM Process: Class 2 lidar was used to create a 1.0 m Raster DEM. Using automated scripting routines within ArcMap, an ERDAS Imagine IMG file was created for each tile. Each surface was reviewed using Global Mapper to check for surface anomalies or incorrect elevations found within the surface. Person who carried out this activity:
    Photo Science, Inc.
    523 Wellington Way
    Lexington, KY
    USA

    859-277-8700 (voice)
    859-277-8901 (FAX)
    bishop@photoscience.com
    Hours_of_Service: Monday through Friday 8:00 AM to 5:00 PM (Eastern Time)
    Contact_Instructions:
    If unable to reach the contact by telephone, please send an email. You should receive a response within 24 hours.
    Data sources used in this process:
    • Validated LAS Datasets
    • Hydro Classification Breaklines
    Data sources produced in this process:
    • Hydro Enforced Raster DEMs
    Date: 04-Jan-2017 (process 6 of 7)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    aallwardt@usgs.gov
    Date: 13-Oct-2020 (process 7 of 7)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
    vatnipp@usgs.gov
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
  2. How accurate are the geographic locations?
  3. How accurate are the heights or depths?
    Fundamental vertical accuracy (FVA) was computed for the raw lidar point cloud swath files. The vertical accuracy was tested with 10 independent survey located in open terrain. These check points were used in the calibration and post processing of the lidar point cloud data. Specifications for this project required that the FVA be 18.13 centimeters (cm) or better AccuracyZ at 95 percent confidence level.
  4. Where are the gaps in the data? What is missing?
    A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data.
  5. How consistent are the relationships among the observations, including topology?
    The lidar data were tested by Photo Science for both vertical and horizontal accuracy. The DEMs are seamless from one tile to the next and have no gaps or no-data areas.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: No restrictions apply to these data.
Use_Constraints:
None. However, users should be aware that temporal changes may have occurred since this dataset was collected and some parts of these data may no longer represent surface conditions. Users should not use these data for critical applications without a full awareness of its limitations. Acknowledgement of the U.S. Geological Survey would be appreciated for products derived from these data.
  1. Who distributes the data set? (Distributor 1 of 1)
    Nathaniel Plant
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, Fla.
    Research Oceanographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727-803-8747 (voice)
    Hours_of_Service: Monday-Friday, 9:00-5:00 Eastern Time
  2. What's the catalog number I need to order this data set? DS 838
  3. What legal disclaimers am I supposed to read?
    Although these data were processed successfully on a computer system at the USGS, no warranty expressed or implied is made regarding the display or utility of the data on any other system, or for general or scientific purposes, nor shall the act of distribution constitute any such warranty. The USGS shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: ERDAS Imagine IMG, zipped
      Network links: http://pubs.usgs.gov/ds/0838/
    • Cost to order the data: None if obtained online; otherwise prices vary.

    • Special instructions:
      Publications are available from USGS Information Services, Box 25286, Federal Center, Denver, CO 80225-0046 (telephone: 1-888-ASK-USGS, e-mail: infoservices@usgs.gov).

Who wrote the metadata?

Dates:
Last modified: 13-Oct-2020
Metadata author:
USGS
Attn: K. Guy
600 4th Street South
St. Petersburg, FL
USA

727-803-8747 (voice)
727-803-2031 (FAX)
kguy@usgs.gov
Hours_of_Service: Monday through Friday 9:00 AM to 5:00 PM (Eastern Time)
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
This page is <https://cmgds.marine.usgs.gov/catalog/spcmsc/metadata_DS-838_DEM_Topographic_Lidar_Survey_July_2013.faq.html>
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