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2011 Delaware Department of Natural Resources and Environmental Control (DNREC) Lidar: Bombay Hook National Wildlife Refuge

browse graphicThis kmz file shows the extent of coverage for the 2011 DNREC Bombay Hook NWR lidar data set.
Terrapoint collected LiDAR for over 177 square kilometers of the Bombay Hook National Wildlife Refuge in Kent County, Delaware. The nominal pulse spacing for this project was no greater than 0.75 meters. This project was collected with a sensor which collects waveform data and provides an intensity value for each discrete pulse extracted from the waveform. GPS Week Time, Intensity, Flightline and echo number attributes were provided for each LiDAR point. Dewberry used proprietary procedures to classify the LAS according to project specifications: 1-Unclassified, 2-Ground, 7-Noise, 9-Water, 12-Overlap. Once the data was received by NOAA CSC, all of the class 7 (noise) points were removed from the data set. Dewberry produced classified LAS and DEMs for the 99 tiles (1700 m x 1700 m) that cover the project area.

Cite this dataset when used as a source.

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    Distribution Formats
    • LAZ
    Distributor DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Point of Contact NOAA Coastal Services Center
    Documentation links not available.
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    • Delaware Department of Natural Resources and Environmental Control
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    • publication: 2012-04-01
    Data Presentation Form: Digital image
    Dataset Progress Status Complete
    Data Update Frequency: As needed
    Purpose: The purpose of this LiDAR data was to produce high accuracy 3D elevation products, including tiled LiDAR in LAS 1.2 format and 1 m cell size Digital Elevation Models (DEMs) for use in coastal management. The LiDAR are processed to the specifications outlined by NOAA CSC in partnership with the Delaware Department of Natural Resources and Environmental Control (DNREC).
    Use Limitations
    • These data depict the elevations at the time of the survey and are only accurate for that time. 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. Any conclusions drawn from analysis of this information are not the responsibility of NOAA or any of its partners. These data are NOT to be used for navigational purposes.
    Time Period: 2011-04-18  to  2011-04-20
    Spatial Reference System: urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters
    Spatial Bounding Box Coordinates:
    N: 39.309361
    S: 39.046286
    E: -75.389419
    W: -75.530873
    Spatial Coverage Map:
    • Bathymetry/Topography
    • DTM
    • Elevation
    • Lidar
    • LAS
    • DEM
    • United States
    • Delaware
    • Bombay Hook National Wildlife Refuge
    • Kent County
    Use Constraints No constraint information available
    Fees Fee information not available.
    Lineage Statement Lineage statement not available.
    • Terrapoint USA
    • Dewberry - Geospatial Services Group
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    • DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
    Processing Steps
    • Terrapoint used their Optech ALTM 3100EA LiDAR sensor to collect the data for the Bombay Hook project. Three flight missions were required to obtain data over the entire project area. Flightlines were flown in a North-South orientation to optimize flying time in regards to the project layout. A combination of Sokkia GSR 2600 and NovAtel DL-4+ dual-frequency GPS receivers were used to support the airborne operations of this survey and to establish the GPS control network. Terrapoint used three existing published survey monuments and one newly established control station to control all flight missions and kinematic and static ground surveys. Airborne GPS kinematic data was processed on-site using GrafNav kinematic On-The-Fly (OTF) software. Flights were flown with a minimum of 6 satellites in view (13 degrees above the horizon) and with a PDOP of better than 4. Distances from base station to aircraft were kept to a maximum of 40 km. For all flights, the GPS data can be classified as excellent, with GPS residuals of 3 cm average or better but no larger than 10 cm being recorded. The initial step of calibration is to verify availability and status of all needed GPS and Laser data against field notes and compile any data if not complete. Subsequently the mission points are output using Optech's Dashmap, initially with default values from Optech or the last mission calibrated for system. The initial point generation for each mission calibration is verified within Microstation/Terrascan for calibration errors. If a calibration error greater than specification is observed within the mission, the roll pitch and scanner scale corrections that need to be applied are calculated. The missions with the new calibration values are regenerated and validated internally once again to ensure quality. All missions are validated against the adjoining missions for relative vertical biases and collected GPS kinematic validation points for absolute vertical accuracy purposes. On a project level, a supplementary coverage check is carried out, to ensure no data voids unreported by Field Operations are present.
    • Dewberry utilizes a variety of software suites for inventory management, classification, and data processing. All LiDAR related processes begin by importing the data into the GeoCue task management software. The swath data is tiled into the client provided tiling schema (1700 m x 1700 m). The tiled data is then opened in Terrascan where Dewberry uses proprietary ground classification routines to remove any non-ground points and generate an accurate ground surface. The first part of the ground routine is to classify all points with a scan angle greater than 20 degrees to class 12, overlap. These points have the highest potential to cause issues in the ground surface. Therefore, they are classified to class 12 immediately where they will not be available for the remaining ground routine. The ground routine consists of three main parameters (building size, iteration angle, and iteration distance); by adjusting these parameters and running several iterations of this routine an initial ground surface is developed. The building size parameter sets a roaming window size. Each tile is loaded with neighboring points from adjacent tiles and the routine classifies the data section by section based on this roaming window size. The second most important parameter is the maximum terrain angle, which sets the highest allowed terrain angle within the model. The ground routine also identifies extremely low or high points that should be excluded from the ground surface and classifies them as class 7, noise. Once the ground routine has been completed a manual quality control routine is done using hillshades, cross-sections, and profiles within the Terrasolid software suite. After this QC step, a peer review and supervisor manual inspection is completed on a percentage of the classified tiles based on the project size and variability of the terrain. After the ground classification corrections were completed, the dataset was processed through a water classification routine that utilizes breaklines compiled by Dewberry to automatically classify hydrographic features. The water classification routine selects ground points within the breakline polygons and automatically classifies them as class 9, water. The fully classified dataset is then processed through Dewberry's comprehensive quality control program. The data was classified as follows: Class 1 = Unclassified. This class includes vegetation, buildings, noise etc. Class 2 = Ground Class 7= Noise (These points were removed from the data set by NOAA CSC during processing for data storage and Digital Coast provisioning). Class 9 = Water Class 12= Overlap Points with a scan angle greater than 20 degrees The LAS header information was verified to contain the following: Class (Integer) GPS Week Time (0.0001 seconds) Easting (0.01 foot) Northing (0.01 foot) Elevation (0.01 foot) Echo Number (Integer 1 to 4) Echo (Integer 1 to 4) Intensity (8 bit integer) Flight Line (Integer) Scan Angle (Integer degree)
    • The NOAA Coastal Services Center (CSC) received the files in las format. The files contained LiDAR elevation as well as intensity values. The data were in Delaware State Plane, NAD83 coordinates and NAVD88 heights. CSC performed the following processing for data storage and Digital Coast provisioning purposes: 1. The data were converted from Delaware State Plane, NAD83 coordinates to geographic coordinates. 2. The data were converted from NAVD88 heights to ellipsoid heights using Geoid09. 3. Data points that were classified as 7 (noise) were removed from the data set. 4. The data were sorted and converted to LAZ format.
    • The NOAA National Geophysical Data Center (NGDC) received lidar data files via ftp transfer from the NOAA Coastal Services Center. The data are currently being served via NOAA CSC Digital Coast at The data can be used to re-populate the system. The data are archived in LAS or LAZ format. The LAS format is an industry standard for LiDAR data developed by the American Society of Photogrammetry and Remote Sensing (ASPRS); LAZ is a loseless compressed version of LAS developed by Martin Isenburg ( The data are exclusively in geographic coordinates (either NAD83 or ITRF94). The data are referenced vertically to the ellipsoid (either GRS80 or ITRF94), allowing for the ability to apply the most up to date geoid model when transforming to orthometric heights.

    Metadata Last Modified: 2013-01-22

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