<metadata>
  <idinfo>
    <citation>
      <citeinfo>
        <origin>Hope Morgan, NC Emergency Management, GIS Manager - GTM</origin>
        <pubdate>20170510</pubdate>
        <title>2016 LiDAR Acquisition and Associated Products for Phase Four Counties in North Carolina</title>
      </citeinfo>
    </citation>
    <descript>
      <abstract>The data set was collected specific to the 2016 Phase Four project area consisting of 20 North Carolina counties. LiDAR data for the project and the validation site was collected by a single aerial vendor on ESP team between February 27, 2016 and April 17, 2016 and between December 9, 2016 and February 21 of 2017 using Geiger-mode Avalanche Photodiode (GmAPD) sensors. The aerial vendor on the ESP team was Harris Corporation (Harris).Two GmAPD (Geiger-mode) sensors (serial numbers 002 and 003) were used for the data collection. The following counties or portions of counties were collected in the February through April, 2016 mobilization: Alleghany, Stokes, Surry, Cleveland, Gaston, Mecklenburg, Cabarrus, Stanly, Union, and Anson. The following counties or portions of counties we collected in the December, 2016 through February, 2017 mobilization: Cleveland, Gaston, Mecklenburg, Cabarrus, Stanly, Wilkes, Yadkin, Forsyth, Alexander, Catawba, Iredell, Davie, Rowan, and Davidson. All data was collected during leaf-off conditions. Ground survey support for the project included the establishment of GPS base stations and the collection of control points used for calibration. All data was delivered in the North Carolina State Plane Coordinate System, with a horizontal datum of NAD83 (2011), vertical datum of NAVD88 (Geoid 12B), in US Survey Feet. Data was delivered tiled to a 2,500 foot by 2,500 foot tiling scheme unless otherwise specified in this product description. All LiDAR was delivered in LASer (LAS) version 1.4 standard format. Products for this project derived from the source LiDAR included: intensity images in GeoTIFF format, hydro-flattening breaklines in ESRI File Geodatabase format, Digital Elevation Models (DEMs) in ESRI Grid format, ESRI Terrain Datasets (by county) in ESRI File Geodatabase format, product and project-level metadata, and project reports to include the Report of Survey, Post-Acquisition Report, and Project Report. All LiDAR and derivative products for this project met the specifications stipulated in Delivery Order 22, the NC LiDAR Standard, and the USGS minimum standards for QL1 LiDAR data. This project was a joint effort between NC Emergency Management, NC Geodetic Survey, and the NCDOT. The following people served as the main representatives for each stakeholder: NC Emergency Management- Hope Morgan (primary contact) and John Dorman; NC Geodetic Survey- Gary Thompson and Watson Ross; NCDOT- Keith Johnston and Marc Swartz, and the United States Geological Survey (USGS).</abstract>
      <purpose>The purpose of this project was to update existing LiDAR data, originally collected between 2000 and 2005, with more accurate and clearly defined LiDAR data utilizing the latest in sensor technology. Although created for the North Carolina Floodplain Mapping Program for specific use in the engineering aspects of floodplain delineation, the data were also developed to address the elevation data requirements of the broader geospatial community. The North Carolina Floodplain Mapping Program was established in response to the extensive damage caused by Hurrican Floyd in 1999.</purpose>
    </descript>
    <timeperd>
      <timeinfo>
        <rngdates>
          <begdate>20160227</begdate>
          <enddate>20170221</enddate>
        </rngdates>
      </timeinfo>
      <current>The data covered by this metadata file are encompassed within the bounding box coordinates provided below.</current>
    </timeperd>
    <status>
      <progress>Complete</progress>
      <update>None planned</update>
    </status>
    <spdom>
      <bounding>
        <westbc>-81.796371</westbc>
        <eastbc>-79.846639</eastbc>
        <northbc>36.607426</northbc>
        <southbc>34.819963</southbc>
      </bounding>
    </spdom>
    <keywords>
      <theme>
        <themekt>None</themekt>
        <themekey>Elevation</themekey>
        <themekey>hydraulic modeling</themekey>
        <themekey>remote sensing</themekey>
        <themekey>LiDAR</themekey>
        <themekey>flood</themekey>
        <themekey>breaklines</themekey>
        <themekey>model</themekey>
        <themekey>DEM</themekey>
        <themekey>elevation</themekey>
        <themekey>floodplain</themekey>
        <themekey>raster</themekey>
        <themekey>Geiger</themekey>
      </theme>
      <theme>
        <themekt>ISO 19115 Topic Categories</themekt>
        <themekey>elevation</themekey>
      </theme>
      <place>
        <placekt>None</placekt>
        <placekey>NC</placekey>
        <placekey>Alleghany County</placekey>
        <placekey>Surry County</placekey>
        <placekey>Stokes County</placekey>
        <placekey>Wilkes County</placekey>
        <placekey>Yadkin County</placekey>
        <placekey>Forsyth County</placekey>
        <placekey>Alexander County</placekey>
        <placekey>Iredell County</placekey>
        <placekey>Davie County</placekey>
        <placekey>Davidson County</placekey>
        <placekey>Catawba County</placekey>
        <placekey>Rowan County</placekey>
        <placekey>Lincoln County</placekey>
        <placekey>Cabarrus County</placekey>
        <placekey>Cleveland County</placekey>
        <placekey>Gaston County</placekey>
        <placekey>Mecklenburg County</placekey>
        <placekey>Union County</placekey>
        <placekey>Anson County</placekey>
        <placekey>Stanly County</placekey>
      </place>
    </keywords>
    <accconst>No restrictions apply to these data.</accconst>
    <useconst>None. However, users should be aware that temporal changes may have occurred since this dataset was collected and that some parts of these data may no longer represent actual surface conditions. Users should not use these data for critical applications without a full awareness of its limitations. Acknowledgement of the North Carolina Emergency Management and the U.S. Geological Survey would be appreciated for products derived from these data.</useconst>
    <ptcontac>
      <cntinfo>
        <cntorgp>
          <cntorg>NC Emergency Management</cntorg>
          <cntper>Hope Morgan</cntper>
        </cntorgp>
        <cntpos>GIS Manager - GTM</cntpos>
        <cntaddr>
          <addrtype>mailing</addrtype>
          <address>NCNG Campus- Bowers Building, 4105 Reedy Creek Road</address>
          <city>Raleigh</city>
          <state>NC</state>
          <postal>27607</postal>
        </cntaddr>
        <cntvoice>919-825-2336</cntvoice>
        <cntfax>919-715-0408</cntfax>
        <cntemail>Hope.Morgan@ncdps.gov</cntemail>
      </cntinfo>
    </ptcontac>
    <ptcontac>
      <cntinfo>
        <cntorgp>
          <cntorg>ESP Associates</cntorg>
          <cntper>Harold Rempel</cntper>
        </cntorgp>
        <cntpos>Project Manager</cntpos>
        <cntaddr>
          <addrtype>mailing</addrtype>
          <address>P.O. Box 7030</address>
          <city>Charlotte</city>
          <state>NC</state>
          <postal>28241</postal>
        </cntaddr>
        <cntvoice>803-835-0851</cntvoice>
        <cntemail>hrempel@espassociates.com</cntemail>
      </cntinfo>
    </ptcontac>
    <ptcontac>
      <cntinfo>
        <cntorgp>
          <cntorg>ESP Associates</cntorg>
          <cntper>Jamey Gray</cntper>
        </cntorgp>
        <cntpos>NC PLS: L-4778</cntpos>
        <cntaddr>
          <addrtype>mailing</addrtype>
          <address>P.O. Box 7030</address>
          <city>Charlotte</city>
          <state>NC</state>
          <postal>28241</postal>
        </cntaddr>
        <cntvoice>803-835-0851</cntvoice>
        <cntemail>jgray@espassociates.com</cntemail>
      </cntinfo>
    </ptcontac>
    <datacred>The ESP Team, consisting of ESP Associates, Surdex Corporation, and Harris Corporation, performed all data collection, ground support, and data processing for this project.</datacred>
    <native>MicroStation Version 8; TerraScan Version 14; ESRI ArcGIS 10.4.1, Windows 7 Operating System; ESP Analyst</native>
  </idinfo>
  <dataqual>
    <posacc>
      <vertacc>
        <vertaccr>Vertical Accuracy Check</vertaccr>
        <qvertpa>
          <vertacce>Lidar was post-processed to meet a Fundamental Vertical Accuracy of 9.25 centimeters RMSEz (in bare ground) or better to support a 1' contour interval. LiDAR ground mass points were compared with surveyed elevations provided by independent contractors to the North Carolina Geodetic Survey.</vertacce>
        </qvertpa>
      </vertacc>
    </posacc>
    <lineage>
      <procstep>
        <procdesc>ESP Associates conducted a ground control survey in support of this project to provide horizontal and vertical positions on predominantly hard surfaces. Bare-earth/low grass surfaces were considered as an alternative in areas where a suitable hard surfaces could not be found. Field procedures were consistent with the National Geodetic Survey Guidelines for Real Time GNSS Networks, March 2011, v.2.0. These procedures included making redundant occupations under different satellite configurations and field conditions for each point. The calibration points were spread throughout the collection area in accordance to the project point layout plan. ESP collected 478 well-distributed GPS survey control points to supplement airborne GPS (ABGPS) accuracy. No control panels were placed as part of this effort. The control was used to facilitate calibration of LiDAR blocks, perform mean adjustment, and conduct preliminary testing of the fundamental vertical accuracy of the data (FVA). The calibration control adhered to the following guidelines: (1) Located only in open terrain, where there was high probability that the sensor would detect the ground surface without influence from surrounding vegetation. (2) On flat or uniformly sloping terrain at least five meters away from any breakline where a change in slope occurs. (3) Checkpoint accuracy satisfied a Local Network accuracy of 5 cm at the 95% confidence level. Accuracy was tested using National Standard for Spatial Data Accuracy guidelines. (4) Photos were taken at each control point location. The North Carolina Geodetic Survey Real-Time Network was used for control for the ground control surveys. Static GPS procedures were used in cell coverage gap areas. The horizontal datum referenced NAD83/2011 Epoch 2010.00 and elevations referenced NAVD88 and used the Geoid12B model to determine orthometric heights. A comprehensive Survey Report was provided to the North Carolina Floodplain Mapping Program, containing the NCPLS certification, list of points, methodology, map book, NGS bench mark tie map, and calibration point datasheets.</procdesc>
        <procdate>20170113</procdate>
      </procstep>
      <procstep>
        <procdesc>LiDAR data for the project and the validation site was collected by a single aerial vendor on ESP team between February 27, 2016 and April 17, 2016 and between December 9, 2016 and February 21 of 2017 using Geiger-mode Avalanche Photodiode (GmAPD) sensors. The aerial vendor on the ESP team was Harris Corporation (Harris). The project design was developed to ensure that the acquired LiDAR data met or exceeded the requirements for the current USGS Quality Level 1 (QL1) and State LiDAR Specifications with an aggregate nominal pulse density (ANPD) of &gt;30 points per square meter (PPSM) for the collected density with a deliverable of 8 PPSM at an aggregate nominal post spacing (ANPS) of &lt;0.35 meters. The project design supported an RMSE of 9.25 cm or better for NVA (USGS specifications modified to State-required 9.25cm from USGS-required 10 cm). The data collection plan was broken into a total of 24 sub-blocks shown in Figure 2. The sub-block plan included limiting flight line acquisition to &lt; 20 minutes, or approximately 92 miles (based on the capabilities of the sensor and aircraft). This reduced the potential for inertial drift by improving inertial precision.  In addition, each block contained sufficient overlap with adjoining blocks to be used for the bundle adjustment calibration procedure.</procdesc>
        <procdate>20170221</procdate>
      </procstep>
      <procstep>
        <procdesc>Calibration of Geiger Mode data differs from that of linear mode systems. Data products are built (aggregated) from multiple data frames captured from multiple look angles. As a result of this process there are no associated flight lines in the output data sets. All data are aggregated into the final output tiles as a seamless dataset. Data and ground (calibration) control points are fed into the enterprise and each line is split into its fore/aft segments and projected to ground space (typically Cartesian) coordinates. Since lines are flown at 55% overlap in opposing directions the resulting four (4) look angles are created. Multiple frames of raw sensor data are transformed to ground Cartesian space (coordinates) to internal production tiles and de-noised to create 4 independent looks in preparation for multi-frame aggregation. Tile to tile auto correlated tie point generation is performed, resulting in thousands of correspondences and high horizontal accuracy and precision. Match point residuals are then computed via ground rotation and translation are then used to perform a final photogrammetric bundle adjustment of the Single Best Estimate of Trajectory (SBET). The adjusted SBET is then used to re-project the raw sensor frames from all 4 looks into ground space tiles which are then de-noised again to create aggregate data tiles at the specified output resolution. These tiles are then automatically re-projected to the required datums and cut into final customer specified seamless tiles.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>Automated filtering was conducted on the LiDAR utilizing macros, containing one or more filtering algorithms, to derive LAS files separated into the different classification groups as defined in the ASPRS point classification requirements of the project, with the exception of overlap classes given the lack of associated flight lines as described in the calibration process step. Automated filters were used to derive the following classifications: Class 1 (unclassified), Class 2 (ground), Class 3 (low vegetation), Class 4 (medium height vegetation), Class 5 (high vegetation), Class 6 (building), Class 7 (low noise), and Class 11 (high noise),  The remaining classifications for the project (such as water and road points) were classified during subsequent process steps in the project and are documented in the respective process step desciptions in this metadata file. During this process step,the macros were tested in several portions of the project area to verify the appropriateness of the filters and adapted when needed to accomodate changes in land cover and terrain features. All team members were provided with identical macros to ensure continuity between production groups. Filtering results were reviewed for gross processing errors prior to the data being released to the next process step. The following file creation difference are present in Geiger-mode LAS files as compared to linear LiDAR files: 1) Intensity – Stored normally as a 16 bit unsigned value however, created from multiple aggregated measurements. This is essentially scaled over the 16 bit range via the number of returns observed for a given reflectance. In Geiger Mode systems intensity is referred to as “Reflectance” and exhibits the same grayscale characteristics as linear systems. 2) Number of Returns (given pulse) - Point records do not contain multi-return data records and are all labeled 1 of 1 returns thus no parent/child relationships exist. This is due to the fact that each frame of data are recorded as single records then post processed (aggregated from multiple looks/measurements) to produce the final point cloud hence, there is no ”given pulse” as with linear systems. 3) Scan Direction Flag – Bit set to zero since this is a palmer (circular continuous) scanning system and is not relevant for the technology since there is no “+-signed” direction. 4) Edge of Flight Line - Bit set to zero since this is a palmer (circular continuous) scanning system and is not relevant for the technology since there is no “end of scan”. 5) Scan Angle – Set to 15 degrees since this is a palmer (fixed Field of View) scanning system. 6) Point Source ID - No flight line (Point Source) record labels exist since final data are built from four (4) look fully aggregated point sets from all flight lines. 7) GPS Time – Time is assigned from the closet single look point to the final aggregate point created. This creates a unique timestamp (record) identifier for each point record within the file(s). It will not follow a logical (increasing time value) time sequence as compared to linear systems.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>A road point classification, Class 13, was incorporated into the LAS classified point clouds by generating road polygons in shapefile format for the majority of state and federally-maintained hard-surface roads. The polygons were mapped using a combination of the LiDAR data, the latest available statewide orthophotography, and a state-provided road line file. Polygons were mapped at edge of pavement where visible and used to automatcially re-classify ground points on the road surface to Class 13. Road features such as private drives, commercial roads, parking lots, and some dirt and gravel roads were not collected or re-classified. Dirt and gravel roads not present in the state-provided file were not collected.The polygon shapefiles used to produce the road classification were a deliverable to the GTM and NCDOT as a reference.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>A bridge point classification, Class 14, was incorporated into the LAS classified point clouds via manual review and classification of bridge features. Analysis and classification of bridges was assisted through the use of ancillary information such as aerial photography, a state-provided bridge point file, and direct interpretation of the LiDAR data. Where possible, large box culverts and other culvert features were not classified as bridge and left in the ground and road classifications. Where possible, technicians identified and classified other types of bridges such as railroad, covered, and pedestrian bridges of substance.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>Breaklines were collected to further define (hydro-flatten) the terrain and enhance the accuracy of the LiDAR DEMs produced at a later process step. Breaklines for this project consisted of two primary categories; water bodies ≥ 2 acres and rivers ≥ 100 feet in width. The hydrographic breaklines were compiled in 3D directly from the LiDAR bare earth data. Color cycles in the TIN model were used to provide a clear indication of where breaklines were to be collected. During this process step, polygon and polyline vertices were created at highly accurate horizontal/vertical coordinates providing for a hydroflattened DEM. Double line drain features (Rivers) were enforced monotonically (have downhill directionality) for linear hydrographic features. The hydro-flattening breaklines were compiled based on the guidelines and principles outlined in the USGS LiDAR Base Specification Version 1.2.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>Water point (Class 9) and breakline proximity point (Class 10) classifications were incorporated into the LAS classified point clouds by using the compiled line work from the previous process step to automatically classify water points and create a buffer of breakline proximity points around the line work. A buffer of 1 foot was used for this classification due to the high resolution of this QL1 data.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>Three densities of hydro-flattened Digital Elevation Models were produced utilizing the Class 2 ground points and collected hydro-breaklines - 3.125 foot (equating to 1 meter), 10 foot, and a 20 foot model. The models were processed using ESP Analyst, in batch, and checked for appearance and flatness of water features.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>Terrain datasets were created by county for each county in the project. The terrains were be stored in individual File Geodatabase format in Arc version 10.4.1. The Terrains were loaded with the processed LiDAR .las file bare earth points, which were converted to multipoint features prior to being loaded. These multipoint features were stored as Surface Feature Type (SFType) “mass points” and were embedded into the Terrain. The most current county boundaries from the State were used as SFType “hard clip”. Any breaklines developed as part of the project were included within the Terrain and contain the appropriate SFType assigned based on the type of input feature. The Pyramid Type was set to the Z Tolerance setting and the Pyramid Properties and Levels were calculated using the Calculate Pyramid Properties dialog within the ESRI Terrain development tool</procdesc>
        <procdate>20170510</procdate>
      </procstep>
      <procstep>
        <procdesc>LiDAR intensity images were generated using the classified LiDAR points and their associated reflectance values with the exception of any noise classes. The intensity images were exported in grayscale, 8-bit, GeoTIFF format using the same tile scheme as the other LiDAR deliverables. The 8-bit format was an Unsigned 8-bit depth with 256 available unique values from 0 to 255.</procdesc>
        <procdate>20170510</procdate>
      </procstep>
    </lineage>
  </dataqual>
  <metainfo>
    <metd>20170510</metd>
    <metc>
      <cntinfo>
        <cntorgp>
          <cntorg>NC Emergency Management</cntorg>
          <cntper>Hope Morgan</cntper>
        </cntorgp>
        <cntpos>GIS Manager - GTM</cntpos>
        <cntaddr>
          <addrtype>mailing</addrtype>
          <address>NCNG Campus- Bowers Building, 4105 Reedy Creek Road</address>
          <city>Raleigh</city>
          <state>NC</state>
          <postal>27607</postal>
        </cntaddr>
        <cntvoice>919-825-2336</cntvoice>
        <cntfax>919-715-0408</cntfax>
        <cntemail>Hope.Morgan@ncdps.gov</cntemail>
      </cntinfo>
    </metc>
    <metstdn>FGDC Content Standard for Digital Geospatial Metadata</metstdn>
    <metstdv>FGDC-STD-001-1998</metstdv>
    <mettc>local time</mettc>
  </metainfo>
</metadata>