2003 Oahu Coastline Lidar Mapping Project

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Frequently anticipated questions:


What does this data set describe?

Title: 2003 Oahu Coastline Lidar Mapping Project
Abstract:
LIDAR data is remotely sensed high-resolution elevation data collected by an airborne collection platform. Using a combination of laser rangefinding, GPS positioning and inertial measurement technologies; LIDAR instruments are able to make highly detailed Digital Elevation Models (DEMs) of the earth's terrain, man-made structures and vegetation. This data was collected over a 100 meter swath of the Oahu, Hawaii coastline with a Leica ALS-40 Aerial Lidar Sensor. Multiple returns were recorded for each pulse in addition to an intensity value.
Supplemental_Information:
The 2003-2005 Hawaii Lidar Data Validation Report may be viewed at: <ftp://ftp.csc.noaa.gov/pub/crs/beachmap/qa_docs/hi>
  1. How should this data set be cited?

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC), 20061018, 2003 Oahu Coastline Lidar Mapping Project: NOAA's Ocean Service, Coastal Services Center (CSC), Charleston, SC.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -158.28200
    East_Bounding_Coordinate: -157.64879
    North_Bounding_Coordinate: 21.728400
    South_Bounding_Coordinate: 21.250250

  3. What does it look like?

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

    Beginning_Date: 21-Oct-2003
    Ending_Date: 07-Dec-2003
    Currentness_Reference: Ground condition

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

    Geospatial_Data_Presentation_Form: Model

  6. How does the data set represent geographic features?

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

      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 0.000000000419255512697643. Longitudes are given to the nearest 0.000000000390594694490901. 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.
      The flattening of the ellipsoid used is 1/298.257.

      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: Ellipsoid
      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?


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?

    n/a

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

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC)
    CEM Project Scientist
    2234 South Hobson Avenue
    Charleston, South Carolina 29405
    United States

    (843) 740-1200 (voice)
    tcm@csc.noaa.gov


Why was the data set created?

The purpose of this mapping project is to create and deliver digital terrain models (DTM), to support the environmental, social, and economic well being of the coast by linking people, information, and technology. The data will support the local Coastal Zone Managers in their decision-making processes.


How was the data set created?

  1. From what previous works were the data drawn?

    Ground Control (source 1 of 2)
    Chappell, Kevin J. , 20031105, Report of Survey - Oahu, Hawaii.

    Type_of_Source_Media: Electronic mail system
    Source_Contribution:
    Kevin Chappell, of Terrasurv and under contract to EarthData International established 30 ground control points along the coastline of the island of Oahu and within a blocked area around Honolulu where the 2005 flight was flown. The points were surveyed using GPS for both vertical and horizontal coordinate values. The horizontal datum used was the North American Datum of 1983 (Pacific Plate Fixed Realization, epoch 2002.0). The vertical datum used was a Local Tidal Datum.

    Aerial Lidar Acquisition (source 2 of 2)
    EarthData Aviation, LLC, 20031207, Aerial Lidar Acquisition over Coastal Oahu, HI.

    Type_of_Source_Media: Firewire Drive
    Source_Contribution:
    Horizons Inc. was contracted by EarthData International to collect ALS-40 Lidar data over the coastal area of Oahu, Hawaii. The project site was flown on October 21 and November 1, 8, 24, 27, and December 7, 2003, using aircraft 2636P. Lidar data was captured using an ALS-40 Lidar system, including an inertial measuring unit (IMU) and a dual frequency GPS receiver. Lidar was obtained at an altitude of 1,524 meters (5,000 feet) above mean terrain, at an average airspeed of 110 knots. Sensor pulse rate was set at 20,000 Hz with a field of view of 20 degrees and a scan rate of 19 Hz. Average swath width of the collected raw lines is 537 meters. Point spacing was 2 meters. Lidar data was recorded in conjunction with airborne GPS and IMU; the stationary GPS receiver was positioned over a control point located at the airport. Recorded digital data was shipped via external hard drive to the production facility for processing. During airborne data collection, an additional GPS receiver was in constant operation over a published National Geodetic Survey (NGS) control point at Honolulu Airport. The coordinate value for temporary control point "PHNL" was determined by a network adjustment to CORS stations EHN1 and HNLC, both of which were tied to the project control network. During the data acquisition, the receivers collected phase data at an epoch rate of 1 Hz. All GPS phase data was post processed with continuous kinematic survey techniques using "On the Fly" (OTF) integer ambiguity resolution. The GPS data was processed with forward and reverse processing algorithms. An adjustment was made to the ellipsoid height of the published point by Terrasurv to reflect Local Tidal Elevation. The results from each process, using the data collected at the airport, were combined to yield a single fixed integer phase differential solution of the aircraft trajectory.

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

    Date: 02-Sep-2005 (process 1 of 3)
    EarthData has developed a unique method for processing lidar data to identify and remove elevation points falling on vegetation, buildings, and other aboveground structures. The algorithms for filtering data were utilized within EarthData's proprietary software and commercial software written by TerraSolid. This software suite of tools provides efficient processing for small to large-scale, projects and has been incorporated into ISO 9001 compliant production work flows. The following is a step-by-step breakdown of the process. 1. Using the lidar data set provided by EarthData, the technician performs calibrations on the data set. 2. Using the lidar data set provided by EarthData, the technician performed a visual inspection of the data to verify that the flight lines overlap correctly. The technician also verified that there were no voids, and that the data covered the project limits. The technician then selected a series of areas from the data set and inspected them where adjacent flight lines overlapped. These overlapping areas were merged and a process which utilizes 3-D Analyst and EarthData's proprietary software was run to detect and color code the differences in elevation values and profiles. The technician reviewed these plots and located the areas that contained systematic errors or distortions that were introduced by the lidar sensor. 3. Systematic distortions highlighted in step 2 were removed and the data was re-inspected. Corrections and adjustments can involve the application of angular deflection or compensation for curvature of the ground surface that can be introduced by crossing from one type of land cover to another. 4. The lidar data for each flight line was trimmed in batch for the removal of the overlap areas between flight lines. The data was checked against a control network to ensure that vertical requirements were maintained. Conversion to the client-specified datum and projections were then completed. The lidar flight line data sets were then segmented into adjoining tiles for batch processing and data management. 5. The initial batch-processing run removed 95% of points falling on vegetation. The algorithm also removed the points that fell on the edge of hard features such as structures, elevated roadways and bridges. 6. The operator interactively processed the data using lidar editing tools. During this final phase the operator generated a TIN based on a desired thematic layer to evaluate the automated classification performed in step 5. This allowed the operator to quickly re-classify points from one layer to another and recreate the TIN surface to see the effects of edits. Geo-referenced images were toggled on or off to aid the operator in identifying problem areas. The data was also examined with an automated profiling tool to aid the operator in the reclassification. 6. The final DEM was written to an ESRI grid format (.flt). 7. The point cloud data were also delivered in LAS format.

    Person who carried out this activity:

    EarthData International
    Attn: Harold Rempel
    Senior Project Manager
    7320 Executive Way
    Frederick, Maryland 21704

    301-948-8550 (voice)
    metadata@earthdata.com

    Data sources used in this process:
    • Lidar

    Data sources produced in this process:

    • Lidar

    Date: 27-Sep-2005 (process 2 of 3)
    The NOAA Coastal Services Center (CSC) received LAS files containing the point cloud elevation data from Earth Data, Inc. CSC performed the following processing on the data to make it available within the Lidar Data Retrieval Tool (LDART): 1. Variable length header records were added to the LAS files to identify projection, datum and sort order. 2. The LAS files were sorted by latitude.

    Person who carried out this activity:

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC)
    CEM Project Scientist
    2234 South Hobson Avenue
    Charleston, South Carolina 29405
    United States

    (843) 740-1200 (voice)
    tcm@csc.noaa.gov

    Date: Feb-2008 (process 3 of 3)
    For data management purposes, the Coastal Services Center converted the data from NAVD88 elevations to ellipsoid elevations using Geoid 99.

    Person who carried out this activity:

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC)
    CEM Project Scientist
    2234 South Hobson Avenue
    Charleston, South Carolina 29405
    United States

    (843) 740-1200 (voice)
    tcm@csc.noaa.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?

    1. Lidar data was collected and processed in accordance with FEMA guidance as published in Appendix A, February, 2002. 2. Lidar data at the interface between the land and ocean was collected (when possible) during periods when tides were predicted to be below mean lower low water based upon NOAA CO-OPS tide predictions for the nearest tidal station. 3. Lidar data accuracy is in accordance with the National Standard for Spatial Accuracy (NSSDA). When compared to 14 GPS static survey points in open non-vegetated areas, at least 95% of the positions have an error less than or equal to 28.8 cm (equivalent to root mean square error of 14.7 cm).

  2. How accurate are the geographic locations?

    The lidar data fully comply with FEMA guidance as published in Appendix A, February, 2002.

  3. How accurate are the heights or depths?

    The lidar data fully comply with FEMA guidance as published in Appendix A, February, 2002 and National Standard for Spatial Accuracy (NSSDA). When compared to 14 GPS static survey points in open non-vegetated areas, at least 95% of the positions have an error less than or equal to 28.8 cm (equivalent to root mean square error of 14.7 cm).

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

    1. EarthData's proprietary software, Checkedb, for verification against ground survey points. 2. Terrascan, for verification of automated and manual editing and final QC of products.

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

    Compliance with the accuracy standard was ensured by the placement of GPS ground control prior to the acquisition of lidar data. The following checks were performed. 1. The ground control and airborne GPS data stream were validated through a fully analytical boresight adjustment. 2. The DTM (Digital Terrain Model) data were checked against the project control. 3. Lidar elevation data was validated through an inspection of edge matching and visual inspection for quality (artifact removal).


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)

    Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC)
    CEM Project Scientist
    2234 South Hobson Avenue
    Charleston, SC 29405-2413

    843-740-1200 (voice)
    tcm@csc.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 analysis of this information are not the responsibility of NOAA or 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/digitalcoast/data/coastallidar>


Who wrote the metadata?

Dates:
Last modified: 05-Jun-2014
Metadata author:
Department of Commerce (DOC), National Oceanic and Atmospheric Administration (NOAA), National Ocean Service (NOS), Coastal Services Center (CSC)
CEM Project Scientist
2234 South Hobson Avenue
Charleston, SC 29405-2413

843-740-1200 (voice)
tcm@csc.noaa.gov

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


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