2004 Connecticut Lidar
LIDAR data is remotely sensed high-resolution elevation data collected by an airborne
collection platform. Using a combination of laser rangefinding, GPS positioning and
inertial measurement technologies; LIDAR instruments are able to make highly detailed
Digital Elevation Models (DEMs) of the earth's terrain, man-made structures and vegetation.
This data was collected at submeter resolution to provide nominal 1m spacing of collected
points. Two returns were recorded for each pulse in addition to an intensity value.
This data set is a raster file of z values with 153 columns and 61 rows. The data
set was generated from a larger data set and includes all valid points within the
requested geographic bounds.
Cite this dataset when used as a source.
|Search and Download
|| Distributor information not available
| Point of Contact
|Data Presentation Form:
|| Digital image
|Dataset Progress Status
|Data Update Frequency:
|| Not planned
||Reflective surface data represents the DEM created by laser energy reflected from
the first surface encountered by the laser pulse. Some energy may continue beyond
this initial surface to be reflected by a subsequent surface as represented by the
Last Return data. Intensity information is captured from the Reflective Surface pulse
and indicates the relative energy returned to the sensor as compared to the energy
transmitted. The Intensity image is not calibrated or normalized but indicates differences
in energy absorption due to the the interaction of the surface materials with laser
energy at the wavelength transmitted by the sensor. Points are classified as on ground
surface or not on ground surface to support creation of a bare earth model from the
data. Open water is classified as not bare ground.
||LIDAR data is used for 3D visualization, elevation based analysis and for feature
|| Unknown to Unknown
|Spatial Reference System:
|Spatial Bounding Box Coordinates:
|Spatial Coverage Map:
- digital elevation model
- United States
- New Haven
- Old Saybrook
- Qunnipiac River
- New Haven Harbor
- Connecticut Coastline
- Connecticut River
| Use Constraints
|| No constraint information available
|| Fee information not available.
Collection System Calibration
- Description of Source: Source Contribution: System Calibration. Minimizes horizontal error caused by IMU
mis-alignment by checking over known range and by comparing positional results from
adjacent flight lines to compute error adjustment function. Source Type: Validation
- Temporal extent used:
|| Lineage statement not available.
- DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
| Processing Steps
- Data Collection: Using a LH Systems ALS50 Light Detection And Ranging (LiDAR) system,
41 flight lines of high density (submeter ground sample distance) data were collected
over areas in coastal Connecticut (approximately 300 square kilometers). Two returns
were recorded for each laser pulse along with an intensity value for each return.
The data acquisition occurred in one (1) mission on October 8, 2004. Three (3) airborne
global positioning system (GPS) base stations were used to support the LiDAR data
acquisition: Moriches 1 continuously operating reference station (CORS) ARP, NGS point
P36, and one station Woolpert located using static GPS positioning methods, Madison
CP. In addition, twenty-two control points were surveyed through fast-static GPS methods
to support the final accuracy analysis and tied into the National Geodetic Survey
(NGS) points Moriches CORS and P36.
- Airborne GPS Processing: 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 overlap between flight lines was removed to provide
a homogeneous coverage, and the coverage was classified to extract a bare earth digital
elevation model (DEM). Airborne GPS is differentially processed using the GrafNAV
V4.10 software by Waypoint Consulting of Calgary, Alberta, Canada. The PDOP and distance
separation is as follows: P36: Maximum PDOP = 3.58 (maximum) Average Distance Separation:
17 km Madison CP: Maximum PDOP = 3.58 (maximum) Average Distance Separation: 19 km
IMU data is processed using the PosPac V4.2 software by Applanix Corporation of Richmond
Hill, Ontario, Canada. The reflective surface is derived using the ALS Post Processor
software by Leica Geosystems GIS & Mapping Division of Atlanta, Georgia. The classification
and quality control (QC) of LiDAR data is carried out using a combination of proprietary
software and TerraScan software by Terrasolid Limited of Helinski, Finland. Two (2)
coverages were delivered in the LAS file format: bare-earth and above ground features.
- IMU data Processing: IMU data provides information concerning roll, pitch and yaw
of collection platform during collection event. IMU information allows the pulse vector
to be properly placed in 3D space allowing the distance from the aircraft reference
point to be properly positioned on the elevation model surface. IMU data is processed
using the PosPac V4.2 software by Applanix Corporation of Richmond Hill, Ontario,
- Reflective Surface Generation: The reflective surface is derived using the ALS Post
Processor software by Leica Geosystems GIS & Mapping Division of Atlanta, Georgia.
- LIDAR Point Classification The classification and quality control (QC) of LiDAR data
is carried out using a combination of proprietary software and TerraScan software
by Terrasolid Limited of Helinski, Finland.
- Output LAS Files Random LIDAR points maintained in UTM coordinate system converted
to Geographic projection with units of Decimal Degrees
- The NOAA Coastal Services Center (CSC) received files in LAS format. The files contained
LiDAR intensity and elevation measurements. CSC performed the following processing
on the data to make it available within the LiDAR Data Retrieval Tool (LDART): 1.
The las files were converted from State Plane coordinates to Geographic coordinates.
2. The las header fields were sorted by latitude and updated. 3. The data were converted
from orthometric to ellipsoidal heights using Geoid03.
- 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
Metadata Last Modified: 2013-05-07
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