2005 Hancock and Jackson Counties, MS Lidar
This metadata record describes the topographic mapping of Hancock and Jackson Counties,
Mississippi during 2005. 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 5m spacing of collected
points. Multiple returns were recorded for each pulse in addition to an intensity
value using a Leica ALS-50 Aerial Lidar Sensor.
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
||These data were originally collected to support flood plain mapping and other coastal
||2005-02-25 to 2005-03-01
|Spatial Reference System:
|Spatial Bounding Box Coordinates:
|Spatial Coverage Map:
- digital elevation model
- Hancock County
- Jackson County
| Use Constraints
|| No constraint information available
|| Fee information not available.
Report of Survey - Hancock & Jackson Counties Mississippt
- Description of Source: Source Contribution: Ground Control. Kevin Chappell, of Terrasurv and under contract
to EarthData International established at total of 40 survey points within Jackson
and Hancock Counties, MS. The survey was completed in two phases; the first phase
consisted of 8 lidar control points in southern Jackson County. The second phase consisted
of 12 additional lidar control points in Jackson County and 20 new lidar control points
in Hancock County. Source Type: electronic mail system
- Temporal extent used:
2005-03-01 to 2005-06-22
Aerial Lidar Acquisition over Jackson County, MS
- Description of Source: Source Contribution: Aerial Lidar Acquisition. EarthData Aviation., was contracted
by EarthData International to collect ALS-50 Lidar data over Hancock and Jackson Counties,
Mississippi. The project site was flown on February 25 and March 1, 10, 11, and 12
using its aircraft with tail number N2636P. Lidar data was captured using an ALS-50
Lidarsystem, including an inertial measuring unit (IMU) and a dual frequency GPS receiver.
Lidar was obtained at an altitude of 3,658 meters (12,000 feet) above mean terrain,
at an average airspeed of 145 knots. Sensor pulse rate was set at 29,900 Hz with a
field of view of 45 degrees and a scan rate of 17 Hz. Average swath width of the collected
raw lines is 3,100 meters. Point spaing was 5 meters. Lidar data was recorded in conjunction
with airborne GPS and IMU; the stationary GPS receiver was positioned over a control
point located at the airport. Recorded digital data was shipped via external hard
drive to the production facility for processing. During airborne data collection,
an additional GPS receiver was in constant operation over a published National Geodetic
Survey (NGS) control point at at KHSA (Stennis International) Airport. The coordinate
value for temporary control point STENNIS (BH2999) was determined by a network adjustment
to CORS stations MOB1 and NDBC , both of which were tied to the project control network.
During the data acquisition, the receivers collected phase data at an epoch rate of
1 Hz. All GPS phase data was post processed with continuous kinematic survey techniques
using "On the Fly" (OTF) integer ambiguity resolution. The GPS data was processed
with forward and reverse processing algorithms. The results from each process, using
the data collected at the airport, were combined to yield a single fixed integer phase
differential solution of the aircraft trajectory. Source Type: Firewire Drive
- Temporal extent used:
2005-02-25 to 2005-03-01
|| Lineage statement not available.
- EarthData International
- DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
| Processing Steps
- EarthData has developed a unique method for processing lidar data to identify and
remove elevation points falling on vegetation, buildings, and other above ground structures.
The algorithms for filtering data were utilized within EarthData's proprietary software
and commercial software written by TerraSolid. This software suite of tools provides
efficient processing for small to large-scale, projects and has been incorporated
into ISO 9001 compliant production work flows. The following is a step-by-step breakdown
of the process. 1. Using the lidar data set provided by EarthData, the technician
performs calibrations on the data set. 2. Using the lidar data set provided by EarthData,
the technician performed a visual inspection of the data to verify that the flight
lines overlap correctly. The technician also verified that there were no voids, and
that the data covered the project limits. The technician then selected a series of
areas from the data set and inspected them where adjacent flight lines overlapped.
These overlapping areas were merged and a process which utilizes 3-D Analyst and EarthData's
proprietary software was run to detect and color code the differences in elevation
values and profiles. The technician reviewed these plots and located the areas that
contained systematic errors or distortions that were introduced by the lidar sensor.
3. Systematic distortions highlighted in step 2 were removed and the data was re-inspected.
Corrections and adjustments can involve the application of angular deflection or compensation
for curvature of the ground surface that can be introduced by crossing from one type
of land cover to another. 4. The lidar data for each flight line was trimmed in batch
for the removal of the overlap areas between flight lines. The data was checked against
a control network to ensure that vertical requirements were maintained. Conversion
to the client-specified datum and projections were then completed. The lidar flight
line data sets were then segmented into adjoining tiles for batch processing and data
management. 5. The initial batch-processing run removed 95% of points falling on vegetation.
The algorithm also removed the points that fell on the edge of hard features such
as structures, elevated roadways and bridges. 6. The operator interactively processed
the data using lidar editing tools. During this final phase the operator generated
a TIN based on a desired thematic layers to evaluate the automated classification
performed in step 5. This allowed the operator to quickly re-classify points from
one layer to another and recreate the TIN surface to see the effects of edits. Geo-referenced
images were toggled on or off to aid the operator in identifying problem areas. The
data was also examined with an automated profiling tool to aid the operator in the
reclassification. 6. The final DEM was written to an ESRI grid format (.flt). 7. The
point cloud data were also delivered in LAS format. 8. Project data was clipped to
a 500-meter buffer outside of the official project boundary.
- 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 UTM coordinates to Geographic coordinates. 2. The las
header fields were sorted by latitude and updated. For data management purposes, the
Coastal Services Center converted the data from NAVD88 elevations to ellipsoid elevations
using Geoid 03.
- 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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