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Metadata Identifier: gov.noaa.csc.maps:2005_baltimore_county_m1382
MD_DataIdentification
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2005 Baltimore County Maryland Lidar |
In the spring of 2005, Sanborn as part of the Dewberry team was contracted
to execute a LiDAR (Light Detection and Ranging) survey campaign to collect the 3-dimensional
positions of a dense set of masspoints for the entire 689 plus square mile project
area of Baltimore County, Maryland. These data are suitable for the development of
a digital elevation model (DEM) to support orthometric photo rectification and contouring.
The lidar first and Last Return value data were obtained from the post processed data
and provided in separate files containing all georeferenced First Return and Last
Return data in an ASCII comma delimited format to the NOAA Coastal Services Center.
For data storage and Digital Coast provisioning purposes, the NOAA Coastal Services
Center converted the ascii data to geographic coordinates, ellipsoid heights in meters,
and las format and created a bare earth data set using an automated algorithm.
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SV_Identification
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2005 Baltimore County Maryland Lidar |
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None |
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North American Datum 1983 |
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resourceProvider |
http://www.epsg-registry.org/export.htm?gml=urn:ogc:def:crs:EPSG::4269 |
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Baltimore County GIS Services |
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pointOfContact |
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Baltimore County, MD GIS Services |
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originator |
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NOAA CSC (originator) |
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DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic
and Atmospheric Administration, U.S. Department of Commerce
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csc.info@noaa.gov |
originator |
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NOAA CSC (publisher) |
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DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic
and Atmospheric Administration, U.S. Department of Commerce
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csc.info@noaa.gov |
publisher |
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NOAA CSC(distributor) |
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DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic
and Atmospheric Administration, U.S. Department of Commerce
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csc.info@noaa.gov |
distributor |
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NOAA CSC (processor) |
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DOC/NOAA/NOS/CSC > Coastal Services Center, National Ocean Service, National Oceanic
and Atmospheric Administration, U.S. Department of Commerce
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csc.info@noaa.gov |
processor |
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EPSG Registry |
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European Petroleum Survey Group |
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publisher |
http://www.epsg-registry.org/ |
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Mike Sutherland(author) |
Mike Sutherland |
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce
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mike.sutherland@noaa.gov |
author |
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Mike Sutherland |
Mike Sutherland |
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce
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mike.sutherland@noaa.gov |
distributor |
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Mike Sutherland (processor) |
Mike Sutherland |
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
of Commerce
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mike.sutherland@noaa.gov |
processor |
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Mr. James Young |
Sanborn Map Company Inc. |
Project Engineer |
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processor |
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http://www.epsg-registry.org/ |
European Petroleum Survey Group Geodetic Parameter Registry |
Registry that accesses the EPSG Geodetic Parameter Dataset, which is a structured
dataset of Coordinate Reference Systems and Coordinate Transformations.
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search |
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http://www.epsg-registry.org/export.htm?gml=urn:ogc:def:crs:EPSG::4269 |
NAD83 |
Link to Geographic Markup Language (GML) description of reference system. |
information |
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Ellipsoid in Meters |
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urn:ogc:def:crs:EPSG::4269 |
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Bounding Box |
Temporal Extent |
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-76.9156 |
-76.3155 |
39.7221 |
39.1934 |
2005-03-18 |
2005-04-15 |
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-76.9156 |
-76.3155 |
39.7221 |
39.1934 |
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Lidar Use Limitation |
These data depict the elevations at the time of the survey and are only
accurate for that time. Users should be aware that temporal changes may
have occurred since this data set was collected and some parts of this data may no
longer represent actual surface conditions. Users should not use this data
for critical applications without a full awareness of its limitations. Any conclusions
drawn from analysis of this information are not the responsibility of NOAA
or any of its partners. These data are NOT to be used for navigational purposes.
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Ellipsoid |
Ellipsoid in Meters |
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NAD83 |
urn:ogc:def:crs:EPSG::4269 |
North American Datum 1983 |
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Step 2- AGPS Processing and Point Cloud- First and Last Return Data
Processing Final post-processing of LiDAR data involves several steps. The airborne
GPS data were post-processed using Waypoint's GravNAVTM software (version 6.03). A
fixed-bias carrier phase solution was computed in both the forward and reverse chronological
directions. All LiDAR acquisition was limited to periods when the PDOP was less than
4.0. The GPS trajectory is combined with the raw IMU data and post-processed using
Applanix Inc.'s POSPROC Kalman Filtering software. This results in a two-fold improvement
in the attitude accuracies over the real-time INS data. The best estimated trajectory
(BET) and refined attitude data are then re-introduced into the Optech REALM software
to compute the laser point-positions - the trajectory is combined with the attitude
data and laser range measurements to produce the 3-dimensional coordinates of the
mass points. The acquired LiDAR data was combined by flight line in a merge process
that eliminated redundant points. The data was clipped into more manageable 1 KM by
1 KM tiles bounds. Noise or anomalous returns were filtered from all data during this
processing step. The data was quality check using commercial software TerraScan.
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2005-01-01T00:00:00 |
Step 1- LIDAR Data Acquisition Sanborn flew the entire project area
as a contiguous block of more than 870 square miles using the ALTM 2050 LIDAR sensor
equipped with Airborne GPS and IMU positioning and orientation units. A total of 54
north south flight lines and 90 east-west flight lines were required to cover the
required entire County project area. Prior to data collection, two AGPS ground stations
were established to support the LiDAR campaign. NGS monument BELL (PID AJ7978) was
used as the northern base station, while NGS monument MTN-B (PID AI4374) was used
as the Martin State Airfield base station. The MTN-B point was used in a previous
survey campaign completed by Sanborn in 2001. Since the MTN-B point has only horizontal
coordinates published, the vertical coordinates generated by the 2001 adjustment were
used. Point MTN-B is First Order horizontal, while BELL is Horizontal Order A and
Vertical Order 2. We tied our network and adjusted our mini network vertically to
a First Class I and five second Class II. The network accuracy is a function of the
fully constrained adjustment and follows very closely the NOAA Technical Memorandum
NOS NGS58 " Guidelines for Establishing GPS Derived Ellipsoid Heights (Standards:
2 cm and 5 cm)," November 1997 yielding sound network adjustment. The combination
(Horizontal & Vertical) achieved the height adjustment meeting the 5 cm standard.
Adjustments constraints for the survey to derive the coordinates The Optech ALTM (Airborne
Laser Terrain Mapping) LiDAR system was calibrated regularly by conducting several
passes over a flat surface of known elevation at the job location. Calibration flights
were performed prior to and following every mission. The calibration parameters were
inserted into the post-processing software before final data processing. The observations
used to establish the fiducial and survey point networks were made at various times
during the LiDAR data collection period. The LiDAR aircraft arrived on site March
18th, 2005 and the LiDAR data collection was accomplished between March 18, 2005 and
April 15, 2005. The flight plan for the project includes the following specifications
to fully meet the project requirements. Single pass density of approximately 1.0 square
meters per sample Average area sampling density - 1.4 square meters per sample Swath
width 728 meters Flight altitude 1000 meters Flight line spacing -589 meters with
125 meters overlap The Scan Frequency- 35 Hz *Scan Angle- 20 degrees Aircraft ground
speed -- 140 knots System Calibration pre and post mission Two GPS base stations within
30 KM. The acquired LiDAR data was combined by flight line in a merge process that
eliminated redundant points. The data was clipped into more manageable 1 KM by 1 KM
tiles bounds. Noise, or anomalous returs were filtered from all data during this processing
step. The data was quality check using commercial software TerraScan.
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2005-01-01T00:00:00 |
Step 3-- Elevation and Coordinate Processing All elevation data was
processed on a point by point basis for ellipsoid to orthometric height conversion
using the National Geodetic Survey (NGS) Geoid Model, GEOID99. Datum and coordinate
system conversion from WGS84 to the Maryland State Plane coordinate system was performed
using U.S. Army Corps of Engineers CorpsCon software algorithms. The LIDAR first and
last return data is filtered to remove the vegetation and above ground manmade features.
Computations are produced for both first and last laser return observations. The ground-filtered
delivery and corresponding regular grid DEM are produced from the last return data.
The first return information provides a useful depiction of the "canopy" within the
project area. Laser point filtering was accomplished using TerraScan LiDAR processing
and modeling software. The bare earth surface generated by TerraScan is used to produce
regular grid DEMs.
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2005-01-01T00:00:00 |
Step 4 First and Last return data Formatting The Terrascan final processed
first and last return data is exported in exported in ASCII comma delimited file format
and clipped to the County' standard tile layout. 837 FR files and 837 LR Data tiles
were supplied on DVD media. QC is performed
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2012-08-01T00:00:00 |
The NOAA Coastal Services Center (CSC) received the first and last
return files in ascii format. NOAA CSC performed the following processing for data
storage and Digital Coast provisioning purposes: 1. The data were filtered for elevation
outliers 2. The data were converted from orthometric heights to ellipsoid heights
using Geoid03 3. The data were converted from Maryland State Plane to geographic coordinates
4. The vertical units of the data were converted from feet to meters 5. A bare earth
data set was created using an automated algorithm. 6. The data were converted to LAZ
format.
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2013-01-22T00:00:00 |
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 heights.
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