Coastal Topography--Northeast Atlantic Coast, Post-Hurricane Sandy, 2012: Digital elevation model (DEM)

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Frequently anticipated questions:


What does this data set describe?

Title:
Coastal Topography--Northeast Atlantic Coast, Post-Hurricane Sandy, 2012: Digital elevation model (DEM)
Abstract:
A DEM was produced for a portion of the New York, Delaware, Maryland, Virginia, and North Carolina coastlines, post-Hurricane Sandy (Sandy was an October 2012 hurricane that made landfall as an extratropical cyclone on the 29th), from remotely sensed, geographically referenced elevation measurements collected by Photo Science, Inc. (Delaware, Maryland, Virgina, and North Carolina) and Woolpert, Inc. (Fire Island, New York) using airborne lidar sensors.
Supplemental_Information:
Processed data products are used by the USGS Coastal and Marine Geology 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.
  1. How might this data set be cited?
    U.S. Geological Survey, 2013, Coastal Topography--Northeast Atlantic Coast, Post-Hurricane Sandy, 2012: Digital elevation model (DEM): U.S. Geological Survey Data Series 765, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -78.82552783
    East_Bounding_Coordinate: -72.69471375
    North_Bounding_Coordinate: 40.81276256
    South_Bounding_Coordinate: 34.55736585
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 05-Nov-2012
    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: 18
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -75.000000
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 1.00000
      Ordinates (y-coordinates) are specified to the nearest 1.00000
      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 6378137.000000.
      The flattening of the ellipsoid used is 1/298.25722210100002.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.15
      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 digital elevation model is composed of a single band, 32-BIT floating point continuous raster (ERDAS Imagine format) representing a gridded form of bare-earth elevation as derived from lidar. Each raster entity contains the bare-earth elevation in meters, relative to NAVD88 (GEOID96). Data ranges from -1.42 to 27.85 meters.
    Entity_and_Attribute_Detail_Citation: Deliverable met specifications in contract.

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?
    Hilary Stockdon
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Research Oceanographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727 803-8747 (x3074) (voice)
    727 803-2031 (FAX)
    hstockdon@usgs.gov
    Hours_of_Service: M-F, 9:00-5:00 ET

Why was the data set created?

The purpose of this project was to derive mean-high-water shoreline, dune crest (DHIGH) and dune toe (DLOW) elevation for a portion of the Eastern United States coastline following Hurricane Sandy, for use as a management tool and to make these data available to natural-resource managers and research scientists.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 05-Nov-2012 (process 1 of 6)
    Using an Optech Gemini lidar sensor, 11 flight lines of high-density data, at a nominal pulse spacing (NPS) of 1 meter, were collected by Woolpert along the southern shore of Long Island, New York (approximately 15 square miles). Data Acquisition Height = 3,500 feet Above Ground Level (AGL) - Aircraft Speed = 125 Knots. Multiple returns were recorded for each laser pulse along with an intensity value for each return. A total of one mission was flown on November 5th. Two airborne global positioning system (GPS) base stations were used in support of the lidar data acquisition. Eight ground control points were surveyed through static methods. The GEOID used to reduce satellite-derived elevations to orthometric heights was GEOID96. Data for the task order is referenced to the UTM Zone 18N, North American Datum of 1983 (NAD83), and North American Vertical Datum of 1988 (NAVD88), in meters. Airborne GPS data was differentially processed and integrated with the post-processed inertial measurement unit (IMU) data to derive a smoothed best estimate of trajectory (SBET). 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. In addition to the LAS deliverables, one layer of coverage was delivered in the ERDAS Imagine (IMG) Format: bare earth. Person who carried out this activity:
    Woolpert, Inc.
    Geospatial Services
    4454 Idea Center Blvd.
    Dayton, OH
    USA

    937 461-5660 (voice)
    937 461-0743 (FAX)
    Hours_of_Service: M-F, 8:00-5:00 ET
    Date: 2012 (process 2 of 6)
    The lidar 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. Person who carried out this activity:
    Woolpert, Inc.
    Geospatial Services
    4454 Idea Center Blvd.
    Dayton, OH
    USA

    937 461-5660 (voice)
    937 461-0743 (FAX)
    Hours_of_Service: M-F, 8:00-5:00 ET
    Date: 07-Nov-2012 (process 3 of 6)
    Once the data acquisition and GPS processing phases are complete, the lidar data were processed immediately by Woolpert to verify the coverage had no voids. The GPS and IMU data were 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. Person who carried out this activity:
    Woolpert, Inc.
    Geospatial Services
    4454 Idea Center Blvd.
    Dayton, OH
    USA

    937 461-5660 (voice)
    937 461-0743 (FAX)
    Hours_of_Service: M-F, 8:00-5:00 ET
    Date: 07-Nov-2012 (process 4 of 6)
    The individual flight lines were inspected by Woolpert 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) classifications. The bare-earth (Class 2 - Ground) lidar points underwent a manual QA/QC step to verify that artifacts have been removed from the bare-earth surface. The surveyed ground control points are used to perform the accuracy checks and statistical analysis of the lidar dataset. Person who carried out this activity:
    Woolpert, Inc.
    Geospatial Services
    4454 Idea Center Blvd.
    Dayton, OH
    USA

    937 461-5660 (voice)
    937 461-0743 (FAX)
    Hours_of_Service: M-F, 8:00-5:00 ET
    Date: 2012 (process 5 of 6)
    Photo Science, Inc. located a total of 29 calibration control points used in the post processing of the lidar data. The points were located on relatively flat terrain on surfaces that generally consisted of grass, gravel, or bare earth. Applanix software (PosPAC MMS) was used in the post processing of the airborne GPS and inertial data, which are critical to the positioning and orientation of the sensor during all flights. POSPac MMS provides the smoothed best estimate of trajectory (SBET) that is necessary for the post processor to develop the point cloud from the lidar missions. The point cloud is the mathematical three-dimensional collection of all returns from all laser pulses as determined from the aerial mission. The GEOID used to reduce satellite derived elevations to orthometric heights was GEOID96. Data for the task order is referenced to the UTM Zone 18N, NAD83, and NAVD88, in meters. At this point the data are ready for analysis, classification, and filtering to generate a bare-earth surface model in which the above ground features are removed from the data set. The point cloud was manipulated by the Optech or Leica software; GeoCue, TerraScan, and TerraModeler software were used for the automated data classification, manual cleanup, and bare-earth generation from the data. Project specific macros were used to classify the ground and to remove the side overlap between parallel flight lines. All data were manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. 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. All Lake Pond and Double Line Drain Island features were checked to ensure that the ground (ASPRS Class 2) were reclassified to the correct classification after the automated classification was completed. All overlap data were processed through automated functionality provided by TerraScan to classify the overlapping flight line data to approved classes by USGS. The overlap data were classified to Class 17 (USGS Overlap Default) and Class 18 (USGS Overlap Ground). These classes were created through automated processes only and were not verified for classification accuracy. Data were then run through additional macros to ensure deliverable classification levels matching the ASPRS LAS Version 1.2 Classification structure. GeoCue functionality was then used to ensure correct LAS Versioning. In-house software was used as a final QA/QC check to provide LAS Analysis of the delivered tiles. QA/QC checks were performed on a per tile level to verify final classification metrics and full LAS header information. Person who carried out this activity:
    Photo Science, Inc.
    Geospatial Services
    4454 Idea Center Blvd.
    Lexington, KY
    USA

    859 277-8700 (voice)
    Hours_of_Service: M-F, 9:00-5:00 ET
    Date: 24-Jan-2017 (process 6 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
  3. What similar or related data should the user be aware of?
    U.S. Geological Survey, 2013, Coastal Topography--Northeast Atlantic Coast, Post-Hurricane Sandy, 2012: Lidar and digital elevation model (DEM) tile index: Data Series 765, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

    Other_Citation_Details:
    This data represents the tile index for lidar data collected for the U.S. Geological Survey in November 2012 following Hurricane Sandy, which made landfall in the eastern United States on October 29th, 2012. The lidar file format (LAS) and digital elevation model (DEM) data are divided into these tiles and filenames match the tile number. The index shows the extent of data collection (portions of the coastline of New York, Delaware, Maryland, Virginia, and North Carolina) and provides tile names to aid in identifying files for data download.

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

  1. How well have the observations been checked?
    The project area required lidar to be collected on 1-meter ground sample distance (GSD) or better and processed to meet a bare earth vertical accuracy of 12.5-centimeters root mean square error (RMSEz) or better.
  2. How accurate are the geographic locations?
    Horizontal accuracy is +/- 0.194 meter at the 95% confidence level.
  3. How accurate are the heights or depths?
    Bare-Earth DEM Fundamental Vertical Accuracy (FVA) Tested 0.147m (14.7 cm) fundamental vertical accuracy at a 95 percent confidence level, derived according to NSSDA (National Standard for Spatial Data Accuracy), in open terrain using 0.075m (7.5 cm) (RMSEz x 1.96000). Tested against the DEM.
  4. Where are the gaps in the data? What is missing?
    These data span from Long Island, New York to Cape Hatteras, North Carolina. The State of New Jersey data were collected using the EAARL-B sensor and those data will be published separately.
  5. How consistent are the relationships among the observations, including topology?
    Data for Fire Island was visually inspected by Woolpert, Inc. Data for Delaware, Maryland, Virginia, and North Carolina were tested by Photo Science, Inc. for both vertical and horizontal accuracy. Although collected on a tile-by-tile basis, breaklines are merged together to produce a single dataset deliverable. Checks are done to ensure that the data is seamless from one tile to the next before being combined and that breaklines meeting the project requirements have been collected across the entire project area. Combining the breaklines with lidar data to create other deliverables is another check of the data. All data are 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: None
Use_Constraints:
The U.S. Geological Survey and National Park Service request to be acknowledged as originators of these data in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
    Attn: Hilary Stockdon
    Research Oceanographer
    600 4th Street South
    St. Petersburg, FL
    USA

    727 803-8747 (x3074) (voice)
    Hours_of_Service: M-F, 9:00-5:00 ET
  2. What's the catalog number I need to order this data set? DS 765
  3. What legal disclaimers am I supposed to read?
    Although these data have been 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?

Who wrote the metadata?

Dates:
Last modified: 18-Mar-2019
Metadata author:
Xan Fredericks
Cherokee Nation Technology Solutions, U.S. Geological Survey, St. Petersburg Coastal and Marine Science Center, St. Petersburg, FL
Lidar Validation and Processing Analyst
600 4th Street South
St. Petersburg, FL
USA

727 803-8747 (x3086) (voice)
afredericks@usgs.gov
Hours_of_Service: M-F, 8:00-4:00 ET
Metadata standard:
FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

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