- 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
| Processing Steps
- Applanix software was used in the post processing of the airborne GPS and inertial
data that is critical to the positioning and orientation of the sensor during all
flights. POSPac MMS provides the smoothed best estimate of trajectory (SBET) that
is necessary for Optech'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 manipulated within the Optech software; GeoCue, TerraScan, and
TerraModeler software was 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. All Class 2 LiDAR data inside of the collected breaklines
were then classified to Class 9 using TerraScan macro functionality. A buffer of 1
meter was also used around each hydro flattened feature. The breakline files were
then translated to ESRI Shapefile format using ESRI conversion tools. Data was then
run through additional macros to ensure deliverable classification levels matching
LAS ASPRS Classification structure. GeoCue functionality was then used to ensure correct
LAS Version. In house software was used as a final QA/QC check to provide LAS Analysis
of the delivered tiles.
- The NOAA Coastal Services Center (CSC) received topographic files in LAS V1.2 format.
The files contained lidar elevation and intensity measurements. The data were received
in UTM Zone 19N (NAD83) coordinates and were vertically referenced to NAVD88 using
the Geoid09 model. The vertical units of the data were meters. CSC performed the following
processing for data storage and Digital Coast provisioning purposes: 1. Elevations
less than -1.0 meters were filtered and removed from the data. 2. The following Classes
(Unknown categories) were combined into Class 1 (Unclassified): 0,3,4,5,6,8,11,13,14,15,16,17,18,20,21,22,23,24,25,26,27,28,29,30,31.
3. Class 19 (Open Water) was combined into Class 9 (Water). 4. The topographic las
files were converted from orthometric (NAVD88) heights to ellipsoidal (NAD83) heights
using Geoid09. 5. The topographic las files were converted from a Projected Coordinate
System (UTM Zone 19N) to a Geographic Coordinate system (NAD83). 6. The topographic
las files' horizontal units were converted from meters to decimal degrees. 7. 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
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
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
the ellipsoid (either GRS80 or ITRF94), allowing for the ability to apply the most
up to date geoid model when transforming to orthometric heights.