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2006 FEMA New Jersey Flood Mitigation Lidar: Hunterdon County

browse graphicThis kmz file shows the extent of coverage for the 2006 FEMA Hunterdon County, NJ lidar data set.
This metadata record describes the lidar topographic elevation mapping of Hunterdon County, NJ that occurred in July 2006. Products generated include lidar point clouds in LAS 1.0 collected with a Leica ALS-50 Aerial Lidar Sensor.

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    Distribution Formats
    • LAZ
    Distributor DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Point of Contact Federal Emergency Management Agency, Region II
    Documentation links not available.
    Originator
    • DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Originator
    • DHS/FEMA > Federal Emergency Management Agency, U.S. Department of Homeland Security
    Publisher
    • DOC/NOAA/NOS/OCM > Office for Coastal Management, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Date(s)
    • publication: 2007-02-26
    Edition: One
    Data Presentation Form: Digital image
    Dataset Progress Status Complete
    Data Update Frequency: Unknown
    Supplemental Information: Watershed Concepts requested the collection of lidar data over Hunterdon County, NJ. In response, EarthData acquired the data on July 17, 2006 using its aircraft with tail number N806CP. Lidar data was acquired using an ALS-50 Lidar Sensor, including an inertial measuring unit (IMU) and a dual frequency GPS receiver. An additional GPS receiver was in constant operation over a published control point set by EarthData at the base of the operations airport which is a secondary airport control station. Terrasurv was tasked to perform a geodetic control survey in support of lidar mapping in Hunterdon County, NJ. The Global Positioning System (GPS) was used in static differential mode to measure the intersection vectors of the network. In addition to six locations chosen for control, a survey point located at the Lehigh valley International Airport was included in the network. This latter station was used a base station by the flight crew during data acquisition. The horizontal datum was the North American Datum of 1983-CORS (NAD83 CORS) and the vertical datum was the North American Vertical Datum of 1988. During the data acquisition, the receivers collected phase data at an epoch rate of 1 Hz. The use of the airport base station ensured that all data capture was within 50 miles of a base station. The solutions from Hunterdon County, NJ were found to be of high integrity and met the accuracy requirements for the project. These accuracy check also verified that the data meets the guidelines outlined in FEMA's Guidelines and Specifications for Flood Hazard Mapping Partners and Appendix 4B, Airborne Light detection and Ranging Systems. The areas of interest were flown at an altitude of 8500 feet above mean terrain. Airspeed - 145 knots Laser Pulse Rate - 38000 Hz Field of View - 40 degrees Scan Rate - 20 Hz Swath Width - 1996 meters
    Purpose: The purpose of this data is to support floodplain mapping efforts as part of FEMA's Map Modernization Program.
    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: Unknown  to  Unknown
    Spatial Reference System: urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters
    Spatial Bounding Box Coordinates:
    N: 40.787876
    S: 40.339414
    E: -74.703495
    W: -75.195215
    Spatial Coverage Map:
    Themes
    • Bathymetry/Topography
    • bare earth
    • DEM
    • digital elevation model
    • elevation
    • floodplain
    • lidar
    • surface model
    Places
    • US
    • New Jersey
    • Hunterdon County
    Use Constraints No constraint information available
    Fees Fee information not available.
    Lineage Statement Lineage statement not available.
    Processor
    • EarthData International
    • DOC/NOAA/NOS/OCM > Office for Coastal Management, 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
    • EarthData has developed a unique method for processing lidar data to identify and remove elevation points falling on vegetation, buildings, and other non-ground structures. The algorithms for filtering data were utilized within EarthData's proprietary software and commercially available 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 workflows. The following process was employed: - Using the lidar data provided by EarthData, the technician performed calibrations of the data. - Using the lidar data provided by EarthData, the technician performed a visual inspection of the data 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 ArcGIS 3D 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. - Identified systematic distortions were removed and the data were 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. - The lidar data for each flightline was trimmed for the removal of the overlap areas between flightlines. 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 flightline datasets were then tiled for batch processing and data management. - The initial batch processing removed 95% of points falling on vegetation. The algorithm also removed the points that fell on the edges of hard features such as buildings, elevated roadways and bridges. - The technician interactively processed the data using lidar editing tools. During this final phase, the data was TINed based on desired thematic layers to evaluate the automated classification previously performed. This allowed the technician to quickly reclassify points from one layer to another and recreate the TIN surface to see the effect of edits. Georeferenced images were toggled on and off to aid in identification of problem areas. The data were also examined with an automated profiling tool to aid in reclassification. - The final DEM was written to las 1.0. - The point cloud data delivered in las 1.0
    • The NOAA Coastal Services Center (CSC) received the files in las format. The files contained Lidar elevation and intensity measurements. The data were projected in New Jersey State Plane coordinates, and referenced to NAVD88 using Geoid 03. CSC performed the following processing steps to the data to make it available within the Digital Coast: 1. The data were converted from New Jersey State Plane (NAD83) coordinates to geographic coordinates (NAD83). 2. The data were converted from NAVD88 (orthometric) heights to GRS80 (ellipsoid) heights using Geoid 03. 3. The LAS data were sorted by latitude and the headers were updated.
    • 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 http://www.csc.noaa.gov/digitalcoast/. 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 (http://www.laszip.org/). 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: 2013-06-11

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