Topographic Lidar Survey of Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana, July 12-14, 2013 -- Classified Point Data

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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 -- Classified Point Data
Abstract:
A topographic lidar survey was conducted July 12-14, 2013 over Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana. Lidar data exchange format (LAS) 1.2 formatted classified point data files 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 lidar data were collected at a nominal pulse spacing (NPS) of 1.0 meter (m). The horizontal projection and datum of the data are Universe Transverse Mercator, zone 16N, North American Datum 1983 (UTM Zone 16N NAD83), meters. The vertical datum is North American Vertical Datum 1988, Geoid 2012a (NAVD88, GEOID12A), meters. Eighty-five LAS files, based on a 2-kilometer by 2-kilometer 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. Lidar_Information Lidar_Collection_Information Lidar_Specification USGS-NGP Base Lidar Specification v1.0 Lidar_Sensor Leica ALS 70 Lidar_Maximum_Returns 4 Lidar_Pulse_Spacing 0.64 Lidar_Density 1.57 Lidar_Flight_Height 1524 Lidar_Flight_Speed 130 Lidar_Scan_Angle 20.0 Lidar_Scan_Frequency 29.6 Lidar_Pulse_Rate 178.4 Lidar_Pulse_Duration 4 Lidar_Pulse_Width 0.35 Lidar_Central_Wavelength 1064 Lidar_Multiple_Pulses_In_Air 0 Lidar_Beam_Divergence 0.22 Lidar_Swath_Width 1109.38 Lidar_Swath_Overlap 11.46% Lidar_Coordinate_Reference_System_Name NAD_1983_UTM_Zone_16N_Meters Lidar_Geoid National Geodetic Survey (NGS) Geoid03 Lidar_Accuracy_Information Lidar_Calculated_Horizontal_Accuracy 0.012 Lidar_Raw_Fundamental_Vertical_Accuracy 0.01 Lidar_LAS_Information Lidar_LAS_Version 1.2 Lidar_LAS_Point_Record_Format 1 Lidar_LAS_Witheld_Point_Identifier Withheld (ignore) points were identified in these files using the standard LAS Withheld bit. Lidar_LAS_Overage_Point_Identifier Swath "overage" points were identified in these files by adding 16 to the standard classification values. Lidar_LAS_Radiometric_Resolution 8 Lidar_LAS_Classification Lidar_LAS_Class_Code 1 Lidar_LAS_Class_Description Processed, but unclassified Lidar_LAS_Classification Lidar_LAS_Class_Code 2 Lidar_LAS_Class_Description Bare earth ground Lidar_LAS_Classification Lidar_LAS_Class_Code 7 Lidar_LAS_Class_Description Noise Lidar_LAS_Classification Lidar_LAS_Class_Code 9 Lidar_LAS_Class_Description Water Lidar_LAS_Classification Lidar_LAS_Class_Code 10 Lidar_LAS_Class_Description Ignored ground Lidar_LAS_Classification Lidar_LAS_Class_Code 17 Lidar_LAS_Class_Description Overlap default (unclassified) Lidar_LAS_Classification Lidar_LAS_Class_Code 18 Lidar_LAS_Class_Description Overlap bare-earth ground
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, 20130904, Topographic Lidar Survey of Dauphin Island, Alabama and Chandeleur, Stake, Grand Gosier and Breton Islands, Louisiana, July 12-14, 2013 -- Classified Point Data: 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: -89.2054218436926
    East_Bounding_Coordinate: -88.0228864379435
    North_Bounding_Coordinate: 30.3016091270762
    South_Bounding_Coordinate: 29.4515909261428
  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: binary point cloud
  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 Point data set. It contains the following vector data types (SDTS terminology):
      • Point
    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?
    *.las
    LAS 1.2 files. The asterisk represents the unique file identifier (See Supplemental Information section). (Source: Photo Science, Inc.)
    X
    UTM zone 16N NAD83 easting in meters. (Source: UTM zone 16N NAD83 coordinate system) varying value range
    Y
    UTM zone 16N NAD83 northing in meters. (Source: UTM zone 16N NAD83 coordinate system) varying value range
    Z
    NAVD88 GEOID12a elevation in meters. (Source: NAVD88 GEOID12a) varying value range
    Intensity
    The intensity value is the integer representation of the pulse return magnitude. This value is optional and system specific. (Source: ASPRS) Integers of varying value range
    Return Number
    The Return Number is the pulse return number for a given output pulse. A given output laser pulse can have many returns, and they must be marked in sequence of return. The first return will have a Return Number of one, the second a Return Number of two, and so on up to five returns. (Source: ASPRS)
    Range of values
    Minimum:1
    Maximum:5
    Number of Returns
    The Number of Returns is the total number of returns for a given pulse. For example, a laser data point may be return two (Return Number) within a total number of five returns. (Source: ASPRS)
    Range of values
    Minimum:1
    Maximum:5
    Scan Direction Flag
    The Scan Direction Flag denotes the direction at which the scanner mirror was traveling at the time of the output pulse. A bit value of 1 is a positive scan direction, and a bit value of 0 is a negative scan direction, where positive scan direction is a scan moving from the left side of the in-track direction to the right side and negative is the opposite. (Source: ASPRS)
    Range of values
    Minimum:0
    Maximum:1
    Edge of Flight Line
    The Edge of Flight Line data bit has a value of 1 only when the point is at the end of a scan. It is the last point on a given scan line before it changes direction. (Source: UTM zone 16N NAD83 coordinate system)
    Range of values
    Minimum:0
    Maximum:1
    Classification
    These data were specifically processed for bare earth (ground). Refer to "Process Steps" for additional information on classification. (Source: ASPRS and Photo Science)
    ValueDefinition
    0Created, never classified
    1Unclassified
    2Ground
    7Low point (noise)
    9Water
    10Ignored ground
    11Reserved
    17Overlap default
    18Overlap ground
    25Reserved
    Scan Angle Rank
    The Scan Angle Rank is a signed one-byte number with a valid range from -90 to 90. The Scan Angle Rank is the angle (rounded to the nearest integer in the absolute value sense)at which the laser point was output from the laser system including the roll of the aircraft. The scan angle is within 1 degree of accuracy from -90 to 90 degrees. Zero degrees is the nadir and -90 degrees is to the left side of the aircraft in the direction of flight. (Source: ASPRS)
    Range of values
    Minimum:-90
    Maximum:90
    User Data
    This field may be used at the user's discretion. (Source: ASPRS) undefined
    Point Source ID
    This value indicates the file from which this point originated. Valid values for this field are 1 to 65,535 inclusive with zero being used for a special case discussed below. The numerical value corresponds to the File Source ID from which this point originated. Zero is reserved as a convenience to system implementers. A Point Source ID of zero implies that this point originated in this file. This also implies that processing software should set the Point Source ID equal to the File Source ID of the file containing this point at some time during processing. (Source: ASPRS)
    Range of values
    Minimum:1
    Maximum:65,535
    GPS Time
    The GPS Time is the double floating point time tag value at which the point was acquired. It is GPS Week Time if the Global Encoding low bit is clear and POSIX Time if the Global Encoding low bit is set (Source: ASPRS) varying value range

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 different 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 6)
    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, was 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 6)
    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 6)
    The bare earth surface is manually reviewed to ensure correct classification on the Class 2 (Ground) points. After the bare-earth surface is finalized, it is 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 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. 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 receive 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 6)
    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 meter 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 to water (ASPRS Class 9) using TerraScan macro functionality. A buffer of 1 meter was also 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: 04-Jan-2017 (process 5 of 6)
    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 6 of 6)
    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?
    FVA was computed for raw lidar point cloud swath files. The vertical accuracy was tested with 10 independent survey checkpoints located in open terrain. These checkpoints were used in the calibration and post processing of the lidar point cloud data. The survey checkpoints were distributed throughout the project area. Specifications for this project require that the FVA be 18.13cm or better AccuracyZ at 95 percent confidence level.
  4. Where are the gaps in the data? What is missing?
    Datasets contain complete coverage of tiles. No points have been removed or excluded. A visual qualitative assessment was performed to ensure data completeness. There are no void areas or missing data. The raw point cloud is of good quality and data passes fundamental vertical accuracy (FVA) specifications.
  5. How consistent are the relationships among the observations, including topology?
    Classified LAS files were tested by Photo Science for both vertical and horizontal accuracy. All data is seamless from one tile to the next; 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: LAS, 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:
U.S. Geological Survey
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_LAS_Topographic_Lidar_Survey_July_2013.faq.html>
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