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2006 MDEQ-FEMA Hinds County Lidar Survey

browse graphicThis kmz file shows the extent of coverage for the 2006 MDEQ Hinds County, MS lidar data set.
This metadata record describes the acquisition and processing of bare earth lidar data, raw point cloud lidar data, lidar intensity data, and floodmap breaklines consisting of a total of 203 sheets for Hinds County, MS. The post-spacing for this project is 4-meter. This project was tasked by Mississippi Geographic Information, LLC (MGI); Work Order No. ED-6. EarthData International, Inc. is a member of MGI and was authorized to undertake this project in accordance with the terms and conditions of the Professional Services Agreement between MGI and the Mississippi Department of Environmental Quality (MDEQ), dated February 17, 2004, and in accordance with MGI Task Order No. 18a.

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 Mississippi Department of Environmental Quality
    601-961-5506
    Stephen_Champlin@deq.state.ms.us
    Associated Resources
    • Lidar Final Report
    Originator
    • DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic and Atmospheric Administration, U.S. Department of Commerce
    Originator
    • Mississippi Department of Environmental Quality (MDEQ)
    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: 2013-09-19
    Data Presentation Form: Digital image
    Dataset Progress Status Complete
    Data Update Frequency: Unknown
    Purpose: The acquisition, processing, and delivery of bare earth lidar data, raw point cloud lidar data, lidar intensity data, and floodmap breaklines covering Hinds County, MS was a coordinated effort between EarthData International, Inc. and MGI, LLC to support MDEM and FEMA flood mapping requirements. Floodmap breaklines are intended to support DFIRM modeling and update only, and will be delivered to MDEQ for use on the DFIRM 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: 2006-04-11  to  2006-04-12
    Spatial Reference System: urn:ogc:def:crs:EPSG::4269 Ellipsoid in Meters
    Spatial Bounding Box Coordinates:
    N: 32.564414
    S: 32.048026
    E: -90.066405
    W: -90.728886
    Spatial Coverage Map:
    Themes
    • Bathymetry/Topography
    • LiDAR
    • Light Detection and Ranging
    • DEM
    • Digital Terrain Model
    • DOGAMI
    • Elevation data
    • Bare earth
    • High-resolution
    • Bare ground
    • DTM
    Places
    • Hinds County
    • Mississippi
    • USA
    Use Constraints No constraint information available
    Fees Fee information not available.
    Source Datasets
    • Aerial Acquisition of Lidar Data for Hinds County, MS
      • Description of Source: Source Contribution: MGI requested the collection of lidar data over Hinds County, MS. In response EarthData International, Inc. acquired the data on April 11 and 12, 2006 using its aircraft with tail number N62912. Lidar data was captured using an ALS50 lidar system, including an inertial measuring unit (IMU) and a dual frequency GPS receiver. An additional GPS receiver was in constant operation over a temporary control point set by EarthData International, Inc. at Hawkins Airport which was later tied into a local network by Waggoner Engineering, Inc. During the data acquisition, the receivers collected phase data at an epoch rate of 1 Hz. The solution from Hinds County, MS was found to be of high integrity and met the accuracy requirements for the project. These accuracy checks also verified that the data meets the guidelines outlined in FEMA's Guidelines and Specifications for Flood Hazard Mapping Partners and Appendix A, section 8, Airborne Light Detection and Ranging (LIDAR) Surveys. Airspeed - 160 knots Laser Pulse Rate - 32900 kHz Field of View - 45 degrees Scan Rate - 18 HzSource Type: firewire
      • Temporal extent used:  unknown  to 
    • Hinds County, Mississippi - Lidar Control
      • Description of Source: Source Contribution: Waggoner Engineering, Inc., under contract to EarthData International, Inc. successfully established ground control for Hinds County, MS. A total of 16 ground control points in Hinds County, MS were acquired. GPS was used to establish the control network. The horizontal datum was the North American Datum of 1983 (NAD83). The vertical datum was the North American Vertical Datum of 1988 (NAVD88).Source Type: electronic mail system
      • Temporal extent used:  unknown  to 
    Lineage Statement Lineage statement not available.
    Processor
    • EarthData International, Inc.
    • EarthData International, Inc.
    • 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
    • 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 1. The technician performs calibrations on the data set. 2. 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 layers 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. 7. The final bare earth was written to an LAS 1.0 format and also converted to ASCII. 8. The point cloud data were delivered in LAS 1.0 format.
    • EarthData utilizes a combination of proprietary and COTS processes to generate intensity images from the lidar data. Intensity images are generated from the full points cloud (minus noise points) and the pixel width is typically matched to the post spacing of the lidar data to achieve the best resolution. The following steps are used to 1. Lidar point cloud is tiled to the deliverable tile layout. 2. All noise points, spikes, and wells are deleted out of the tiles. 3. An EarthData proprietary piece of software, EEBN2TIF is then used to process out the intensity values of the lidar. At this point, the pixel size is selected based on best fit or to match the client specification if noted in the SOW. 4. The software then generates TIF and TFW files for each tile. 5. ArcView is used to review and QC the tiles before delivery. 6. The lidar intensity data were delivered in TIF format.
    • It should be noted that the breaklines developed for use in the H&H modeling should not be confused with traditional stereo-graphic or field survey derived breaklines. The elevation component of the 3D streamlines (breaklines) is derived from the lowest adjacent bare earth lidar point and adjusted to ensure that the streams flow downstream. The best elevation that can be derived for the 3D streamlines will be the water surface elevation on the date that the lidar data was acquired. The elevations in the 3D streamlines will not represent the underwater elevations for streams due to the fact that lidar data cannot collect bathymetry information. Watershed Concepts and EarthData have done considerable research generating breaklines from lidar data. Current H&H modeling practices rely heavily on mass points and breaklines to create a realistic TIN surface for hydrologic and hydraulic modeling. Lidar data consists only of points, which are not suited to defining sharp breaks on terrain. The problem is most pronounced across stream channels, where lidar is not able to define the stream banks clearly. Furthermore lidar does not reflect off water; therefore, no reliable elevation points will exist within the stream channel itself. The TIN surface generated from lidar data alone is unsuitable for H&H modeling. Watershed Concepts engineers have studied the sensitivity of the 100-year flood boundary to the definition of stream channel geometry. The surface created with both lidar points and breaklines improves channel definitions for hydraulic cross section takeoffs and better defines the stream invert. It is not necessary to create breaklines on the top and bottom of stream banks; minor modifications to the cross sections and stream inverts can be made based on field survey data as necessary. In the 100-year flood, most of the flooded cross sectional area occurs in the overbank; therefore, creating a more refined channel definition from the lidar data is not cost effective. The lidar TIN is used simply as the basis for the overbank definition. Our research indicates that breaklines are required at the stream centerline for smaller streams with widths less than 50 feet. For larger streams (widths greater than 50 feet, breaklines are needed on the left and right water edge lines. Collection of photography and stereo compilation of the breaklines is not cost-effective for this purpose. Watershed Concepts and EarthData have developed techniques to synthesize 3D breaklines using digital orthophotos and lidar data. These breaklines can be digitized in 2D from orthophotos, approximating the stream bank in areas of significant tree overhang. A bounding polygon, created from the edge of bank lines, is used to remove all points within the channel. Automatic processes assign elevations to the vertices of the centerline based on surrounding lidar points. The lines are then smoothed to ensure a continuous downhill flow. Edge-of-bank vertices are adjusted vertically to match the stream centerline vertices. A new TIN can then be created from the remaining lidar points and newly created breaklines. The new TIN clearly defines the stream channel. For this project, breaklines were generated in the matter described above for all streams draining greater than approximately one square mile. 2D lines defining the centerline and banks of those streams were manually digitized into ESRI shape file format from 2005 imagery. The streamlines were then processed against the bare earth lidar as described above. The new 3D lines were then viewed in profile to correct any anomalous vertices or remove errant points from the lidar DTM, which cause unrealistic "spikes" or "dips" in the breakline. The 3D breaklines were delivered in ESRI shapefile format.
    • The NOAA Coastal Services Center (CSC) received the files in las format. The files contained LiDAR elevation and intensity measurements. The data were in Mississippi State Plane West (2301, feet) coordinates and NAVD88 (Geoid03) vertical datum (feet). CSC performed the following processing for data storage and Digital Coast provisioning purposes: 1. The data were converted from State Plane (2301) coordinates to geographic coordinates. 2. The data were converted from NAVD88 (orthometric) heights to GRS80 (ellipsoid) heights using Geoid03. 3. 8 laz tiles had coordinates falling outside of the header boundary. These tiles were re-tiled to remove any data points falling outside of the header boundary. 4. All laz tiles were received with all points classed as Class 1 (unclassified); the laz tiles were put through lasground.exe (lastools) which uses an algorithm to define which points fall as class 2 (Ground). 5. The data were sorted by time. 6. 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: 2013-10-17

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