2005 St. Johns River Water Management District (SJRWMD) Lidar: Western Seminole County,
This data set consists of a bare earth data set of 498 files covering a geographic
area of 175 square miles in western Seminole County, Florida and includes small portions
of adjacent Orange and Lake Counties. The lidar data was collected June 5-7, 2005.
This data set seems to contain only model keypoints (points that are a thinned data
set that is intended to remove extraneous data such as trees and points that are deemed
redundant to the final bare earth product) that are classified as ground points. As
a result, there are a lower number of points than in a full mass point lidar data
set; and it is recommended that the data be downloaded as points and used with a TIN
(Triangulated Irregular Network) or similar algorithm to produce a bare earth surface.
Cite this dataset when used as a source.
|Search and Download
|| Distributor information not available
| Point of Contact
||St. Johns River Water Management District (SJRWMD)
Lidar Dataset Supplemental Information
- St. Johns River Water Management District (SJRWMD)
|Data Presentation Form:
|| Digital image
|Dataset Progress Status
|Data Update Frequency:
||This data set depicts information about geographic features within the project area
and is to be used for purposes defined by the SJRWMD.
||2005-06-05 to 2005-06-07
|Spatial Reference System:
|Spatial Bounding Box Coordinates:
|Spatial Coverage Map:
- Lidar Mapping
- Bare earth
- Intensity image
- United States
- Western Seminole County
- Portions of Orange County
- Portions of Lake County
| Use Constraints
|| No constraint information available
|| Fee information not available.
|| Lineage statement not available.
- Aerial Cartographics of America, Inc.
- DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department
| Processing Steps
- LiDAR Data Acquisition -- The Lidar data was collected utilizing an Optech ALTM (Airborne
Laser Terrain Mapper) 2025 in a Cessna 208 Grand Caravan aircraft on June 5, 2005
between 0930 and 1150 hours at an altitude of 3000' AGL. Data was also collected starting
June 6, 2005 at 1830 hours and ending on June 7 at 0900 hours. The configuration used
a scan half-angle of +/-17 degrees, a laser pulse repetition frequency of 25 kilohertz,
and a flying speed of approximately 80 knots. Airborne GPS using a Novatel dual frequency
GPS receiver was accomplished during the flight session to provide positional information
for the Lidar platform. Simultaneous acquisition of ground base station data was performed
using a Novatel and Leica SR9500 dual frequency receivers for the June 5, 2005 session.
Two Leica SR9500 dual frequency GPS receivers were used for the second session on
June 6-7, 2005. Each station remained in operation for the duration of the project
flight. The ground base stations were set up over National Geodetic Survey (NGS) monuments
AK0205 (Designation Number I4 71 A14) and AK7045 (Designation Number GIS 0472 CAS
1). Positional information on these monuments was obtained from Data Sheets retrieved
from the NGS website (http://www.ngs.noaa.gov). The GPS data from the ground base
stations and the airborne platform were processed together using Applanix POSPac 4.2
software module POSGPS. All adjustments were referenced to WGS84. The Inertial Measurement
Unit (IMU) solution was accomplished to provide information regarding the attitude
of the Lidar platform using the Applanix POSPac 4.2 software module POSProc. This
solution was integrated with the Airborne GPS and adjusted using a Kalman filter in
a forward/reverse solution to provide a Smoothed Best Estimate of Trajectory (SBET).
Laser ranging from the airborne platform was accomplished using Realm 3.2 processing
software to provide XYZ ground positions for each point. The final horizontal values
were output in Universal Transverse Mercator (UTM), Zone 17, units are meters. The
horizontal datum conforms to the current Florida High Accuracy Reference Network (HARN)
adjustment for the North American Datum of 1983. The Vertical Datum is the North American
Vertical Datum of 1988 (NAVD88), units are feet.
- Classification of the laser data to extract above ground features such as buildings
and vegetation leaving only bare earth ground points was performed using Terrasolid
Ltd. Terrascan software (Version 003.003). The data was separated into five (5) separate
sets 502 files representing Bald Earth First Pulse, Bald Earth Last Pulse, Extracted
Features First Pulse, Extracted Features Last Pulse, and LAS format. The Bald Earth
Last Pulse best represents the natural ground and is the file upon which all accuracy
statements are based. The Extracted Features First Pulse best represents the canopy
data that includes all features determined to be above the natural ground.
- The NOAA Coastal Services Center (CSC) received the bare earth files in ASCII format.
The data were Universal Transverse Mercator (UTM), Zone 17, units in meters, NAVD88
vertical datum and the vertical units of measure were feet. CSC performed the following
processing to the ASCII data to make it available within Digital Coast: 1. The data
were converted from UTM coordinates to geographic coordinates. 2. The data were converted
from NAVD88 (orthometric) heights to GRS80 (ellipsoid) heights using Geoid 03. 3.
The LAS data were sorted by latitude and the headers were updated.
- 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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