2012 USACE Post-Hurricane Sandy Topographic LiDAR: Eastern Long Island, New York
This kmz file shows the extent of coverage for the 2012 USACE Post-Hurricane Sandy
Long Island lidar data set.
TASK ORDER NAME: EASTERN LONG ISLAND, NEW YORK LIDAR ACQUISITION FOR HURRICANE SANDY
RESPONSE CONTRACT NUMBER: W912P9-10-D-0533 TASK ORDER NUMBER: W81C8X23208588 Woolpert
Project Number: 72903 Q. USACE required high-resolution digital elevation data developed
from airborne LiDAR technology for the Eastern Long Island, New York. The Area of
Interest (AOI) consisted of one hundred sixteen (116) square miles in the North Atlantic
Division. The final LiDAR data was delivered in a UTM projection tiling format, based
on a modular layout. The tiles were clipped to eliminate overlap between adjacent
tiles. The 1000 meter x 1000 meter tile file name was derived from the National Grid
naming convention. The data originally was collected with the following specifications:
LAS v1.2 classified point cloud NAD83 UTM Zone 18N Meters, NAVD88 GEOID12A Meters.
Cite this dataset when used as a source.
|Search and Download
|| Distributor information not available
| Point of Contact
||US Army Corps of Engineers St. Louis District
Documentation links not available.
- US Army Corps of Engineers (USACE) St. Louis District
|Data Presentation Form:
|| Digital image
|Dataset Progress Status
|Data Update Frequency:
|| As needed
||The data will be used by the USACE to generate digital elevation models and contours
for use in, damage assessment to USACE projects, engineering design and design reviews,
conservation planning, research, delivery, floodplain mapping, and hydrologic modeling
utilizing LiDAR technology. The task order required that the LiDAR data was to be
acquired within six (6) days of receiving Notice to Proceed (NTP). The project data
will consist of high accuracy classified bare-earth LiDAR data in LAS format well
as raster digital elevation models per task order requirements. The specifications
are based upon the U.S. Geological Survey National Geospatial Program Lidar Base Specifications
1.0, which may be viewed at http://pub.usgs.gov/tm/11b4/.
||2012-11-14 to 2012-11-15
|Spatial Reference System:
|Spatial Bounding Box Coordinates:
|Spatial Coverage Map:
- United States
- New York
- Long Island
| Use Constraints
|| No constraint information available
|| Fee information not available.
|| Lineage statement not available.
| Processing Steps
- Using an Optech Gemini LiDAR Sensor, 21 flight lines of high density data, at a nominal
pulse spacing (NPS) of 1 meter, were collected along the Eastern Long Island, New
York (approximately one hundred sixteen (116) square miles). Data Acquisition Height
= 5,500 feet AGL - Aircraft Speed = 125 Knots. Multiple returns were recorded for
each laser pulse along with an intensity value for each return. A total of two (2)
missions were flown during a period from November 14, 2012 through November 15, 2012.
One airborne global positioning system (GPS) base station was used in support of the
LiDAR data acquisition. Eighteen (18) ground control points were surveyed through
static methods. The geoid used to reduce satellite derived elevations to orthometric
heights was Geoid12A. Data for the task order is referenced to the UTM Zone 18N, North
American Datum of 1983 (NAD83), and NAVD88, in Meters. Airborne GPS data was differentially
processed and integrated with the post processed IMU data to derive a smoothed best
estimate of trajectory (SBET). The SBET was used to reduce the LiDAR slant range measurements
to a raw reflective surface for each flight line. The coverage was classified to extract
a bare earth digital elevation model (DEM) and separate last returns. In addition
to the LAS deliverables, one layer of coverage was delivered in the ArcGrid Format:
- The LiDAR system calibration and system performance is verified on a periodic basis
using Woolpert's calibration range. The calibration range consists of a large building
and runway. The edges of the building and control points along the runway have been
located using conventional survey methods. Inertial measurement unit (IMU) misalignment
angles and horizontal accuracy are calculated by comparing the position of the building
edges between opposing flight lines. The scanner scale factor and vertical accuracy
is calculated through comparison of LiDAR data against control points along the runway.
Field calibration is performed on all flight lines to refine the IMU misalignment
angles. IMU misalignment angles are calculated from the relative displacement of features
within the overlap region of adjacent (and opposing) flight lines. The raw LiDAR data
is reduced using the refined misalignment angles.
- Once the data acquisition and GPS processing phases are complete, the LiDAR data was
processed immediately to verify the coverage had no voids. The GPS and IMU data was
post processed using differential and Kalman filter algorithms to derive a best estimate
of trajectory. The quality of the solution was verified to be consistent with the
accuracy requirements of the project.
- The individual flight lines were inspected to ensure the systematic and residual errors
have been identified and removed. Then, the flight lines were compared to adjacent
flight lines for any mismatches to obtain a homogenous coverage throughout the project
area. The point cloud underwent a classification process to determine bare-earth points
and non-ground points utilizing "first and only" as well as "last of many" LiDAR returns.
This process determined Default (Class 1), Ground (Class 2),Noise (Class 7), Model
Key Points (Class 8), and Overlap (Class 12) classifications. The bare-earth (Class
2 - Ground) LiDAR points underwent a manual QA/QC step to verify that artifacts have
been removed from the bare-earth surface. The surveyed ground control points are used
to perform the accuracy checks and statistical analysis of the LiDAR dataset.
- The NOAA Coastal Services Center (CSC) received topographic files in LAS format. The
files contained lidar elevation and intensity measurements. The data were received
in NAD83 UTM18N, meters Projected Coordinates and were vertically referenced to NAVD88
using the Geoid12a model. The vertical units of the data were meters. CSC performed
the following processing for data storage and Digital Coast provisioning purposes:
1. The topographic las files were converted from orthometric (NAVD88) heights to ellipsoidal
heights using Geoid12a. 2. The topographic las files were converted from Projected
Coordinates (Nad83 UTM18N, meters) to Geographic Coordinates (NAD83, decimal degrees).
3. 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.
Metadata Last Modified: 2013-02-20
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