2009 USGS-NJDEP Lidar: Salem County (Non-CAFRA Area)

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This graphic shows the lidar coverage for the non-CAFRA area of Salem County, NJ.

Date that the source FGDC record was last modified.

Converted from FGDC Content Standards for Digital Geospatial Metadata (version FGDC-STD-001-1998) using 'fgdc_to_inport_xml.pl' script. Contact Tyler Christensen (NOS) for details.

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LiDAR points were used to produce the deliverables. | Source Geospatial Form: digital data | Type of Source Media: hard drive

Leica software was used in the post-processing of the airborne GPS and inertial data that is critical to the positioning of the sensor during all flights. This software suite includes Applanix's PosPac and Waypoint's GrafNav solutions. PosPac provides the smoothed best estimate of trajectory (SBET) that is necessary for Leica's post processor to develop the point cloud from the Lidar missions. The point cloud is the mathematical three dimensional collection of all returns from all laser pulses as determined from the aerial mission. At this point this data is ready for analysis, classification, and filtering to generate a bare earth surface model in which the above ground features are removed from the data set.

The point cloud was created using Leica's ALS Post Processor software. GeoCue was used in the creation of some of the files needed in downstream processing, as well as in the tiling of the dataset into more manageable file sizes. The TerraScan and TerraModeler software packages are then used for the automated data classification, manual cleanup, and bare earth generation from this data. Project specific macros were used to classify the ground and to remove the side overlap between parallel flight lines. All data was manually reviewed and any remaining artifacts removed using functionality provided by TerraScan and TerraModeler. QT Modeler was used as a final check of the bare earth dataset. GeoCue was then used to create the deliverable LAS 1.1 files for both the All Point Cloud Data and the Bare Earth. In-house software was then used to perform final statistical analysis of the classes in the LAS files as a quality control measure.

Hydro Enforcement

Utilizing the provided 1:2,400-scale digital hydrography, the Photo Science Team developed 3-dimensional breaklines from lidargrammetry and the intensity images. The Team created LiDAR stereo-mates using GeoCue LiDAR Pak software, and then used Socet Set and lidargrammetry to stereo-compile the hydro breaklines. Lidargrammetry, described on pages 227-230 of "Digital Elevation Model Technologies and Applications: The DEM Users Manual," 2nd edition, is a new technology that we have found superior for 3D breakline generation from LiDAR data. The breaklines are topologically correct and maintain monotonicity to ensure the downward flow of water. These breaklines were also used to classify water features in the LAS data.

Hydro Enforced DEM Development

The bare-earth DEM was hydro-enforced utilizing the criteria stated in Task Order Items C.1.b(iii) and C.1.c (i) but was supplemented by the criteria in Appendix F - Data Dictionary and Hydro Breakline Stereo Compilation Rules to better match the final product of the 2-0 meter DEM. Due to the small grid size of 2 meters, criteria such as "Streams are considered Double line streams when the width of the stream measures 1/4 inch or more based on a 1:24,000 scale" would have produce a result whereby a single line stream would be 500 feet or less. Therefore a single line stream could only be represented by the width of one cell which would only be 2 meters, which would not have been a good representation of the stream width. Appendix F defines the criteria for which all hydro lines were collected to ensure that streams flow downhill, that double line streams be flattened, that water course shall be connected through bridges and culverts and that puddling or false depressions be resolved.

The NOAA Office for Coastal Management (OCM) received files in LAS format. The files contained LiDAR intensity and elevation measurements.

OCM performed the following processing on the data to make it available within Digital Coast:

1. The LAS files were corrected based on GPS time-week to adjusted-GPS standard time (week 1524) and outlier elevations were removed. Though this was later recognized to be incorrect, the GPS dates were left as is. To fix this week/date issue, data would have needed to be delivered as swath. Extensive work would be needed, as well as flightlines in a ingestable format. Please notice, some tile dates will be a GPS week off, though the report specifies by date the areas flown on specific dates.

2. The data were converted from New Jersey State Plane (ft) to geographic coordinates.

2. The data were converted from NAVD88 heights (ft) to ellipsoid heights using Geoid03.

3. The LAS header fields were sorted by latitude and updated.