2007 US Army Corps of Engineers (USACE), Jacksonville District US Virgin Islands LiDAR

Metadata also available as - [Outline] - [Parseable text] - [XML]

Frequently anticipated questions:


What does this data set describe?

Title:
2007 US Army Corps of Engineers (USACE), Jacksonville District US Virgin Islands LiDAR
Abstract:
This Light Detection and Ranging (LiDAR) bare-earth classified LAS dataset is a topographic survey conducted for the USACE USVI LiDAR Project. These data were produced for The Corps of Engineers Jacksonville District. The USVI LiDAR Survey consists of the islands of St. Croix, St. Thomas, and St. John. The LiDAR point cloud was flown at a density sufficient to support the Federal Emergency Management Agency (FEMA) guidelines and specifications. The Atlantic Group acquired the USVI LiDAR Survey between November 16, 2007 and November 29, 2007. The USVI LiDAR survey was collected under the guidance of a Professional Mapper/Surveyor.
Supplemental_Information:
A footprint of this data set may be viewed in Google Earth at: <ftp://ftp.csc.noaa.gov/pub/crs/beachmap/qa_docs/vi/2007_USACE_Virgin_Islands_Lidar.kmz>
  1. How should this data set be cited?

    Corps of Engineers, Jacksonville District, and Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC), 2008, 2007 US Army Corps of Engineers (USACE), Jacksonville District US Virgin Islands LiDAR: NOAA's Ocean Service, Coastal Services Center (CSC), Charleston, SC.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -65.091685
    East_Bounding_Coordinate: -64.549985
    North_Bounding_Coordinate: 18.431784
    South_Bounding_Coordinate: 17.673984

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Beginning_Date: 16-Nov-2007
    Ending_Date: 29-Nov-2007
    Currentness_Reference: publication date

  5. What is the general form of this data set?

  6. How does the data set represent geographic features?

    1. How are geographic features stored in the data set?

      Indirect_Spatial_Reference: US Virgin Islands
      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?

      Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0000001. Longitudes are given to the nearest 0.0000001. Latitude and longitude values are specified in Decimal degrees.

      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 1/298.257222.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: Ellipsoid
      Altitude_Resolution: 0.001
      Altitude_Distance_Units: Meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates

  7. How does the data set describe geographic features?


Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)

  2. Who also contributed to the data set?

    Acknowledgement of the Corp of Engineers, Jacksonville District would be appreciated in products derived from these data.

  3. To whom should users address questions about the data?

    3001 Inc
    LiDAR Department
    501 Robert Blvd
    Slidell, Louisiana 70458
    USA

    (985) 661 - 3001 (voice)
    (985) 649 - 5082 (FAX)
    lidar@3001inc.com

    Hours_of_Service: 8:00 - 5:00 CDT


Why was the data set created?

The USVI LiDAR Project Survey data will support the creation of Federal Emergency Management Agency Flood Insurance Rate Maps (FEMA FIRM) and an integrated ground and surface water model.


How was the data set created?

  1. From what previous works were the data drawn?

    Not provided (source 1 of 1)
    Corps of Engineers, Jacksonville District, 2008, The US Virgin Islands LiDAR Survey: Corps of Engineers, Jacksonville District, Jacksonville, FL.

    Type_of_Source_Media: digital tape media
    Source_Scale_Denominator: 24000
    Source_Contribution:
    This Light Detection and Ranging (LiDAR) LAS dataset is a topographic survey conducted for the USACE USVI LiDAR Project. These data were produced for The Corps of Engineers Jacksonville District. The USVI LiDAR Survey consists of the islands of St. Croix, St. Thomas, and St. John. The LiDAR point cloud was flown at a density sufficient to support the Federal Emergency Management Agency (FEMA) guidelines and specifications. 3001 Inc. acquired the USVI LiDAR Survey between November 16, 2007 and November 29, 2007. The USVI LiDAR Survey was collected under the guidance of a Professional Mapper/Surveyor.

  2. How were the data generated, processed, and modified?

    Date: 09-Aug-2007 (process 1 of 8)
    The Airborne Global Position System (ABGPS), inertial measurement unit (IMU), and raw scans are collected during the LiDAR aerial survey. The ABGPS monitors the xyz position of the sensor and the IMU monitors the orientation of the aircraft. During the aerial survey laser pulses reflected from features on the surface and are detected by the receiver optics and collected by the data logger. GPS locations are based on data collected by receivers on the aircraft and base stations on the ground. The ground base stations are placed no more than 35 km radius from the flight survey area.

    Person who carried out this activity:

    3001 Inc.
    LiDAR Department
    501 Robert Blvd
    Slidell, Louisiana 70458
    USA

    (985) 661 - 3001 (voice)
    (985) 649 - 5082 (FAX)
    lidar@3001inc.com

    Hours_of_Service: 8:00 - 5:00 CDT
    Date: 2008 (process 2 of 8)
    The ABGPS, IMU, and raw scans are integrated using proprietary software developed by the Leica Geosystems and delivered with the Leica ALS50 System. The resultant file is in a LAS binary file format. The LAS file version 1.1 format can be easily transferred from one file format to another. It is a binary file format that maintains information specific to the LiDAR data (return #, intensity value, xyz, etc.). The resultant points are produced in the Florida State Plane West Zone coordinate system, with units in feet and referenced to the NAD83 horizontal datum and GRS80/Geoid03 vertical datum.

    Person who carried out this activity:

    3001 Inc.
    LiDAR Department
    501 Robert Blvd
    Slidell, Louisiana 70458
    USA

    (985) 661 - 3001 (voice)
    (985) 649 - 5082 (FAX)
    lidar@3001inc.com

    Hours_of_Service: 8:00 - 5:00 CDT
    Date: 31-Aug-2007 (process 3 of 8)
    The unedited data are classified to facilitate the application of the appropriate feature extraction filters. A combination of proprietary filters is applied as appropriate for the production of bare-earth digital terrain models (DTMs). Interactive editing methods are applied to those areas where it is inappropriate or impossible to use the feature extraction filters, based upon the design criteria and/or limitations of the relevant filters. These same feature extraction filters are used to produce elevation height surfaces.

    Person who carried out this activity:

    3001 Inc.
    LiDAR Department
    501 Robert Blvd
    Slidell, Louisiana 70458
    USA

    (985) 661 - 3001 (voice)
    (985) 649 - 5082 (FAX)
    lidar@3001inc.com

    Hours_of_Service: 8:00 - 5:00 CDT
    Date: 31-Aug-2007 (process 4 of 8)
    Filtered and edited data are subjected to rigorous QA/QC according to the 3001 Inc. Quality Control Plan and procedures. Very briefly, a series of quantitative and visual procedures are employed to validate the accuracy and consistency of the filtered and edited data. Ground control is established by 3001, Inc. and GPS-derived ground control points (GCPs) points in various areas of dominant and prescribed land cover. These points are coded according to landcover, surface material, and ground control suitability. A suitable number of points are selected for calculation of a statistically significant accuracy assessment as per the requirements of the National Standard for Spatial Data Accuracy. A spatial proximity analysis is used to select edited LiDAR data points within a specified distance of the relevant GCPs. A search radius decision rule is applied with consideration of terrain complexity, cumulative error, and adequate sample size. Accuracy validation and evaluation is accomplished using proprietary software to apply relevant statistical routines for calculation of Root Mean Square Error (RMSE) and the National Standard for Spatial Data Accuracy (NSSDA) according to Federal Geographic Data Committee (FGDC) specifications.

    Person who carried out this activity:

    3001 Inc.
    LiDAR Department
    501 Robert Blvd.
    Slidell, Louisiana 70458
    USA

    (985) 661 - 3001 (voice)
    (985) 649 - 5082 (FAX)
    lidar@3001inc.com

    Hours_of_Service: 8:00 - 5:00 CDT
    Date: 31-Aug-2007 (process 5 of 8)
    The LiDAR mass points were delivered in American Society for Photogrammetry and Remote Sensing LAS 1.1 format. The header file for each dataset is complete as define by the LAS 1.1 specification. In addition the following fields are included: Flight Date Julian, Year, and Class. The data were classified as follows: Class 1 = Unclassified- this class includes vegetation, buildings, noise etc.; Class 2 = Ground Class 7 = Noise Class 9 = Water Class 12 = Overlap

    Person who carried out this activity:

    3001 Inc.
    LiDAR Department
    501 Robert Blvd
    Slidell, Louisiana 70458
    USA

    (985) 661 - 3001 (voice)
    (985) 649 - 5082 (FAX)
    lidar@3001inc.com

    Hours_of_Service: 8:00 - 5:00 CDT
    Date: 2007 (process 6 of 8)
    A triangulated irregular network (TIN) is a set of irregularly spaced points that contain an explicit topographic value. Each point is a vertice and is connected to any three points to represent an area of uniform topography. TINs retain precise topological location and are excellent sources for statistical calculations. The TINs were created in Terrasolid's "Terrascan" software. The first step of the process included the separation of the bare-earth points from the artifacts. The breaklines (vectors) are then concerted to x, y, z (ASCII) files and imported into the bare-earth mass points. The final step is to create the TIN using an ESRI Arc macro language (aml) script. To ensure the quality of the TIN each TIN is viewed independently to ensure that the hydro-breaklines are enforced and that the vegetation has been removed.

    Date: 2007 (process 7 of 8)
    The breaklines were constructed under the model representation that water courses vary linearly in elevation or are constant in elevation between critical points established in the breakline model. These breaklines were determined from LiDAR and orthophoto data of specific dates and that model the land/water contributions and extents on those dates. The 3-D vector line work was created using stereo-compilation, digitizing, and manual editing. A thorough QC procedure was implemented to verify the elevation of the breaklines and to ensure no zero elevations were found except in coastal areas where it is possible to find z values equal to mean sea level. The breaklines are hydrologically correct 3-D product that represents a continuous dendritic network. This dataset is topologically correct. Stream and river features that are 0.5 miles or greater in length will be captured. Features that are 8 feet are less in width shall be captured as a single breaklines. Features greater than 8 feet in width shall be captured as double breakline features. All features will be captured as three-dimensional breaklines. Coastal shorelines shall be captured as three-dimensional linear features. Coastal breaklines will merge seamlessly with linear hydrographic features at the approximate maximum extent of tidal influence. The shoreline of islands within water bodies shall be captured as three-dimensional breaklines. Terramodel software was used to display the edited LiDAR points and associated GEOTIFF orthophotos to construct breaklines for the water's edge of wide channel rivers and canals, the shoreline of lakes and the shoreline of islands within water bodies. Breakline elevations were linearly ramped between identified critical elevation points along flowing water courses or were set at a fixed level for lakes based on the lowest observed shoreline elevation or water return elevation. The breakline files are edge-matched and a shapefile for the project was created. Three-dimensional breaklines were derived through on screen digitizing based on the LiDAR data and orthophotography. The line work was captured as two dimensional lines with x/y coordinates only. Principal breaklines that support hydrologic and hydraulic models were captured which includes stream shorelines and hydraulic features such as dams, bridges, and culverts that constrict or impede the flow of water.

    Date: Nov-2010 (process 8 of 8)
    The NOAA Coastal Services Center (CSC) received files in LAS format. The files contained LiDAR intensity and elevation measurements. CSC performed the following processing on the data to make it available within Digital Coast: 1. The data were converted from State Plane Puerto Rico coordinates to UTM Zone 20 coordinates. 2. The data were converted from NAVD88 feet to NAVD88 meters. 3. The data were re-tiled in MARS and all point classifications were set to 0 (class 0). 4. The data were filtered to Bare Earth (class 2) and Unclassified (class 1) using an automated process in LASEdit. 5. The data were converted from UTM coordinates to geographic coordinates. 6. The data were converted from NAVD88 heights to ellipsoid heights using Geoid03. 7. The LAS header fields were sorted by latitude and updated.

    Person who carried out this activity:

    NOAA Coastal Services Center
    Clearinghouse Manager
    2234 South Hobson Ave.
    Charleston, SC 29405
    US

    843-740-1210 (voice)
    clearinghouse@noaa.gov

  3. What similar or related data should the user be aware of?

    Corps of Engineers, Jacksonville District, 2008, US Virgin Islands LiDAR Survey: Corps of Engineers, Jacksonville District, Jacksonville, FL.


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

  1. How well have the observations been checked?

    The USVI LiDAR Project Survey data will support the creation of Federal Emergency Management Agency Flood Insurance Rate Maps (FEMA FIRM) and an integrated ground and surface water model.

  2. How accurate are the geographic locations?

    All ground control processing and adjustment is performed using published coordinate horizontal and vertical datums (e.g. NGS CORS). For deliverables, Corpscon for Windows Version 5.11.08 (geoid 03) was used for horizontal and vertical datum conversion as well as for coordinate system conversion purposes (e.g. UTM to State Plane).

  3. How accurate are the heights or depths?

    The accuracy assessment was performed using a standard method to compute the root mean square error (RMSE) based on a comparison of ground control points (GCP) and filtered LiDAR data points. Filtered LiDAR data has had vegetation and cultural features removed and by analysis represents bare-earth elevations. The RMSE figure was used to compute the vertical National Standard for Spatial Data Accuracy (NSSDA). Ground control was established by 3001, Inc. A spatial proximity analysis was used to select edited LiDAR data points contiguous to the relevant GCPs. A search radius decision rule is applied with consideration of terrain complexity, cumulative error, and adequate sample size. Cumulative error results from the errors inherent in the various sources of horizontal measurement. These sources include the airborne GPS, GCPs, and the uncertainty of the accuracy of the LiDAR data points. This accuracy is achieved prior to the sub-sampling that occurs through integration with the inertial measurement unit (IMU) positions that are recorded. It is unclear at this time whether the initial accuracy is maintained. The horizontal accuracy of the GCPs is estimated to be in the range of approximately 1 to 1.6 inches. Finally, sample size was considered. The specification for the National Standard for Spatial Data Accuracy is a minimum of 20 points to conduct a statistically significant accuracy evaluation (Minnesota Planning, 1999, Positional Accuracy Handbook, Minnesota Planning Land Management Information Center, St. Paul, Minnesota, p.3). Most statistical texts indicate that a minimum of 30 sample points provide a reasonable approximation of a normal distribution. The intent of the NSSDA is to reflect the geographic area of interest and the distribution of error in the data set (Federal Geographic Data Committee, 1998, Geospatial National Standard for Spatial Data Accuracy, Federal Geographic Data Committee Secretariat, Reston, Virginia, p.3-4). Additional steps were taken to ensure the vertical accuracy of the LiDAR data including: Step 1: Precision Bore sighting (Check Edge-matching) Step 2: Compare the LiDAR data to the Field Survey (Field survey is to FEMA specifications and more stringent internal specifications) Step 3: Automated Filtering Step 4: Manual Editing (Quality Control) Step 5: 3-D digitizing and Photogrammetric Compilation of hydrographic breaklines

  4. Where are the gaps in the data? What is missing?

    The USVI LiDAR Project Survey data will support the creation of Federal Emergency Management Agency Flood Insurance Rate Maps (FEMA FIRM) and an integrated ground and surface water model. The bare-earth surface will contain voids in areas that were densely vegetated, covered by bridges, buildings, water, fresh asphalt, sand etc.

  5. How consistent are the relationships among the observations, including topology?

    This Light Detection and Ranging (LiDAR) LAS dataset is a topographic survey conducted for the USACE USVI LiDAR Project. These data were produced for The Corps of Engineers Jacksonville District. The USVI LiDAR Survey consists of the islands of St. Croix, St. Thomas, and St. John. The LiDAR point cloud was flown at a density sufficient to support the Federal Emergency Management Agency (FEMA) guidelines and specifications. 3001 Inc. acquired the USVI LiDAR Survey between November 16, 2007 and November 29, 2007. The USVI LiDAR Survey was collected under the guidance of a Professional Mapper/Surveyor.


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:
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.

  1. Who distributes the data set? (Distributor 1 of 1)

    NOAA Coastal Services Center
    Clearinghouse Manager
    2234 South Hobson Ave.
    Charleston, SC 29405-2413

    843-740-1210 (voice)
    clearinghouse@noaa.gov

  2. What's the catalog number I need to order this data set?

    Downloadable Data

  3. What legal disclaimers am I supposed to read?

    Any conclusions drawn from the analysis of this information are not the responsibility of Corps of Engineers, Jacksonville District, the Coastal Services Center, or its partners.

  4. How can I download or order the data?

  5. Is there some other way to get the data?

    This data can be obtained on-line at the following URL: <http://www.csc.noaa.gov/lidar>


Who wrote the metadata?

Dates:
Last modified: 17-Jul-2014
Metadata author:
NOAA Coastal Services Center
Clearinghouse Manager
Charleston, SC 29405-2413

843-740-1210 (voice)
clearinghouse@noaa.gov

Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)


Generated by mp version 2.9.13 on Fri Oct 31 10:42:25 2014