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2006 Federal Emergency Management Agency (FEMA) Topographic LiDAR: Coastal Connecticut

browse graphicThis kmz file shows the extent of coverage for the 2006 FEMA Coastal Connecticut lidar data set.
LIDAR data is remotely sensed high-resolution elevation data collected by an airborne collection platform. By positioning laser range finding with the use of 1 second GPS with 100hz inertial measurement unit corrections; Terrapoint's LIDAR instruments are able to make highly detailed geospatial elevation products of the ground, man-made structures and vegetation. The LiDAR flightlines for this project was planned for a 50% acquisition overlap. The nominal resolution of this project without overlap is 1.25m. Four returns were recorded for each pulse in addition to an intensity value. GPS Week Time, Intensity, Flightline and number attributes were provided for each LiDAR point. Data is provided as random points, in LAS v1.0 format, classified according to ASPRS Class Code 2=Ground 1=Undefined. Water is included in the bare earth ground model, except where the entire tile is covered by water. The following regions of Connecticut are included in this project: Fairfield County - 130 square kilometers New Haven - 170 square kilometers Middlesex - 29 square kilometers New London - 157 square kilometers Please note that the LiDAR intensity is not calibrated or normalized. The intensity value is meant to provide relative signal return strengths for features imaged by the sensor.

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 National Oceanic and Atmospheric Administration (NOAA)
    (843) 740-1200
    Documentation links not available.
    Originator
    • DOC/NOAA/NOS/CSC > Coastal Services Center, 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/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Date(s)
    • publication: 2013-04-01
    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 based geospatial products for coastal flood mapping.
    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: 2006-12-16  to  2006-12-18
    Spatial Reference System: urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters
    Spatial Bounding Box Coordinates:
    N: 41.540542
    S: 40.979296
    E: -71.829101
    W: -73.659952
    Spatial Coverage Map:
    Themes
    • Topography/Bathymetry
    • ASPRS standards
    • elevation
    • LAS_v1.0
    • laser
    • LiDAR
    • OPTECH_3100EA
    Places
    • Fairfield County
    • New Haven
    • Middlesex
    • New London
    • Connecticut
    • United States
    Use Constraints No constraint information available
    Fees Fee information not available.
    Lineage Statement Lineage statement not available.
    Processor
    • Terrapoint USA
    • Terrapoint USA
    • 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
    • - General Overview The Airborne LiDAR survey was conducted using an OPTECH 3100EA flying at a nominal height of 1550 metres AGL with a total angular coverage of 40 degrees. Flight line spacing was nominally 564 metres providing overlap of 50% on adjacent flight lines. Lines were flown in east/west and north/south orientated blocks to best optimize flying time considering the layout for the project. - Aircraft A Piper Navajo, registration C-FQQB was used for the survey. This aircraft has a flight range of approximately 6.5 hours and was flown at an average altitude of 1550, thereby encountering flying altitudes of approximately 1550 metres above sea level (ASL). The aircraft was staged from the East Haven CT Airport, and ferried daily to the project site for flight operations. - GPS Receivers 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. - Number of Flights and Flight Lines For both Connecticut and Rhode Island Coastline Sites; a total of 6 missions were flown for this project with flight times ranging approximately 31 hours under good meteorological and GPS conditions. 72 flight lines were flown over the Connecticut Coastline site to provide complete coverage.
    • - Airborne GPS Kinematic 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 (13o above the horizon) and with a PDOP of better than 4.5. Distances from base station to aircraft were kept to a maximum of 35 km, to ensure a strong OTF (On-The-Fly) solution. For all flights, the GPS data can be classified as excellent, with GPS residuals of 5cm average but no larger than 12 cm being recorded. - Calculation of 3D laser points (raw data) The post-processing software to derive X, Y, Z values from roll, pitch, yaw, and range is Optech's Realm. - Classification and Editing The data was processed using the software TerraScan, and following the methodology described herein. The initial step is the setup of the TerraScan project, which is done by importing client provided tile boundary index encompassing the entire project areas. The 3D laser point clouds, in binary format, were imported into the TerraScan project and divided in 1407 tiles, as per the contract specifications. tiled, the laser points were classified using a proprietary routine in TerraScan. This routine removes any obvious outliers from the dataset following which the ground layer is extracted from the point cloud. The ground extraction process encompassed in this routine takes place by building an iterative surface model. This surface model is generated using three main parameters: building size, iteration angle and iteration distance. The initial model is based on low points being selected by a "roaming window" with the assumption is that these are the ground points. The size of this roaming window is determined by the building size parameter. The low points are triangulated and the remaining points are evaluated and subsequently added to the model if they meet the iteration angle and distance constraints. This process is repeated until no additional points are added within an iteration. A second critical parameter is the maximum terrain angle constraint, which determines the maximum terrain angle allowed within the classification model. The data is then manually quality controlled with the use of hillshading, cross-sections and profiles. Any points found to be of class vegetation, building or error during the quality control process, are removed from the ground model and placed on the appropriate layer. An integrity check is also performed simultaneously to verify that ground features such as rock cuts, elevated roads and crests are present. Once data has been cleaned and complete, it is then reviewed by a supervisor via manual inspection and through the use of a hillshade mosaic of the entire project area. - Projection Transformation The data was processed in the native UTM zone in meters and then transformed to the Connecticut State Plane final projection system and US survey feet using an in-house transformation software which uses the Coorpscon DLL.
    • The NOAA Coastal Services Center (CSC) received the topographic files in LAZ V1.0 format. The files contained lidar elevation measurements. The data were received in Connecticut State Plane coordinates, NAD83 (Zone 0600) and were vertically referenced to NAVD88 using the Geoid03 model. The vertical units of the data were feet. CSC performed the following processing for data storage and Digital Coast provisioning purposes: 1. The topographic las files were converted from a Projected Coordinate System (Connecticut SP 0600) to a Geographic Coordinate system (NAD83). 2. The topographic las files' horizontal units were converted from US survey feet to decimal degrees. 3. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal heights using Geoid03. 4. The topographic las files' vertical units were converted from survey feet to meters. 5. The data were 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 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: 2013-04-25

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