Title:
2002 Upper Texas Coast Lidar Point Data, Gulf of Mexico Shoreline in the Northeast 3.75-Minute Quadrant of the Lake Como 7.5-Minute Quadrangle: Post Fay Survey
Abstract:
This data set contains elevation data derived from a lidar survey approximately 300m wide of the Gulf of Mexico shoreline in the Northeast Lake Como quarter-quadrangle on Galveston Island Texas. The geographic extent of the data set is equivalent to the quarter-quadrangle plus 30 meters of overedge. The data is created by combining data collected using an Optech Inc. Airborne Laser Terrain Mapper (ALTM) 1225 in combination with geodetic quality Global Positioning System (GPS) airborne and ground-based receivers. The Bureau of Economic Geology, the University of Texas at Austin owns and operates an ALTM 1225 system (serial number 99d118). This system is installed in a single engine Cessna 206 (tail number N4589U) owned and operated by the Texas State Aircraft Pooling Board. The lidar data described by this document was collected on 18 September 2002 (26102) between 20:34 and 00:08 UTC (actual data collection). Conditions on that day were low clouds at 335m Above Ground Level (AGL), haze, and occasional showers. 99d118 instrument settings for this flight were; laser pulse rate: 25kHz, scanner rate: 26Hz, scan angle: +/-20deg, beam divergence: wide, altitude: 300-490m AGL, and ground speed: 70-106kts. Three GPS base stations, 2 Ashtech and 1 Trimble 4000SSI receivers (backup), were operating during the survey. The three base stations were at the following locations: one 3.5km south of San Luis Pass, one at the Scholes International Airport Galveston, and one on the seawall at Rollover Pass.
This data set consists of 1687100 records of x,y, and z values. The data set was generated from a larger data set and includes all valid points within the requested geographic bounds.
Supplemental information:
The ALTM 1225 has the following specifications: operating altitude = 410-2,000 m AGL; laser pulse rate = 25 kHz; laser scan angle = variable from 0 to +/-20deg from nadir; scanning frequency = variable, 28 Hz at the 20deg scan angle; and beam divergence = 0.2 milliradian (half angle, 1/e). The ALTM 1225 does not digitize and record the waveform of the laser reflection, but records the range and backscatter intensity of the first and last laser reflection using a constant-fraction discriminator and two Timing Interval Meters (TIM).
ALTM elevation points are computed using three sets of data: laser ranges and their associated scan angles, platform position and orientation information, and calibration data and mounting parameters (Wehr and Lohr, 1999). Global Positioning System (GPS) receivers in the aircraft and on the ground provide platform positioning. The GPS receivers record pseudo-range and phase information for post-processing. Platform orientation information comes from an Inertial Measurement Unit (IMU) containing three orthogonal accelerometers and gyroscopes. An aided-Inertial Navigation System (INS) solution for the aircraft's attitude is estimated from the IMU output and the GPS information.
Wehr, A. and U. Lohr, 1999, Airborne laser scanning - an introduction and overview, ISPRS Journal of Photogrammetry and Remote Sensing, vol. 54, no.2-3, pp.68-82.
1. How should this data set be cited?
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Origin:
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Bureau of Economic Geology, University of Texas at Austin
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Pub Date:
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20061017
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Title:
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2002 Upper Texas Coast Lidar Point Data, Gulf of Mexico Shoreline in the Northeast 3.75-Minute Quadrant of the Lake Como 7.5-Minute Quadrangle: Post Fay Survey
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2. What geographic area does the data set cover?
Bounding coordinates:
West:
-95.568694
East:
-93.831419
North:
29.688483
South:
28.797218
3. What does it look like?
4. What is the temporal coverage of the data set?
5. What is the geospatial form of this data set?
6. How does the data set represent geographic features?
How are geographic features stored in the data set?
As a
Point
data set
What is the coordinate system used to represent geographic features?
7. What are the contents of this dataset?
8. What were the instruments or sensors used to collect the data
9. What satellites, boats or other platforms housed the instruments?
10. What missions supported the platforms?
11. What online links are contained in this metadata record?
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Who produced the data set?
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Why was the data set created?
The data described in this document are being used to create Digital Elevation Models of the Texas Coast. The DEMs are being used to map the position of the shoreline along the Gulf of Mexico coast of Texas for determining rates of shoreline change following Tropical Storm Fay (September 2002).
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How was the data set created?
2. What changes have been made?
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Event |
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20030211
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Transfer raw ALTM 1225 flight data, airborne GPS data collected at 1 Hz using Ashtech receiver, and ground-based GPS data collected at 1 Hz using Ashtech and Trimble 4000SSI receivers to NT workstation. Generate decimated lidar point file from above three data sets using Optech's Realm 2.27 software. This is a 9-column ASCII data set with the following format: time tag; first pulse Easting, Northing, HAE; last pulse Easting, Northing, HAE; first pulse intensity; and last pulse intensity. View decimated lidar point file to check data coverage (i.e. sufficient overlap of flight lines and point spacing).
Compute base station coordinates using National Geodetic Survey's PAGES software. Computed aircraft trajectories for both base stations using National Geodetic Survey's KINPOS software. Coordinates for base stations and trajectories are in the International Terrestrial Reference Frame of 2000 (ITRF2000) datum. Trajectories from both base stations were merged into one. Weighting for trajectory merge is based upon baseline length (distance from base station) and solution RMS. Transformed trajectory solution from ITRF2000 to North American Datum of 1983 (NAD83).
Use NAD83 trajectories and aircraft inertial measurement unit data in Applanix's POSProc version 2.1.4 to compute an optimal 50Hz inertial navigation solution.
Substitute the aircraft position and attitude information from the inertial navigation solution into Realm 2.27. Extract calibration area data set from lidar point file for quality control and instrument calibration checks. If necessary, use multiple iterations to adjust calibration parameters (pitch, roll, and scale) and reprocess sample data set. Then generate entire lidar point file (9-column ASCII file).
Transfer point file from NT workstation to UNIX workstation. Parse the 9-column lidar point file into 3.75-minute quarter-quadrangle components and apply elevation bias correction (determined during calibration step). There are some points in the file that only contain 5-columns. These are points that either the first or last pulse was not recorded.
Processing done over 20020918-20030211.
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20030224
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The 9-column post-processed data from University of Texas were provided in UTM projection (Zone 15) referenced to NAD83 with vertical elevations in meters referenced to the Geodetic Reference System 80 (GRS80) ellipsoid. The xyz values for the last return were extracted from the 9-column file. The data were converted to geographic coordinates using General Cartographic Transformation Program software developed by the United States Geological Survey. A vertical datum transformation was performed to convert vertical elevations referenced to GRS80 ellipsoid to NAVD88 using National Geodetic Survey (NGS) GEOID99 grids. The data were then converted to a binary format and loaded into the LIDAR Data Retrieval Tool (LDART) database.
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20060103
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The NOAA National Geophysical Data Center (NGDC) received Lidar data files on external harddrive. The disk contains LiDAR data from the NOAA Coastal Services Center. This data is currently being served via LDART at http://www.csc.noaa.gov/ldart . This data can be used to re-populate the system. The data are provided on this disk in two forms, ascii x,y,z data and also in LAS format. LAS format is an industry standard for serving LiDAR data. The data are exclusively in geographic coordinates, however, the datums used vary. Most is NAD 83, however some is in ITRF. Vertical systems include both ellipsoid (ITRF and NAD 83) and NAVD 88. For NAVD 88 values, Geiod 03 is primarily used; however, data received in NAVD 88 prior to 2003 was processed using Geoid 99.
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3. Who is the person responsible for change?
University Station Box X
Austin
Texas
78713
United States
Roberto: 512-471-0342
John: 512-471-4951
(voice)
512-471-0140
(fax)
Roberto: oskar@mail.utexas.edu
John: john.andrews@beg.utexas.edu
Coastal Remote Sensing Program
2234 South Hobson Avenue
Charleston
South Carolina
29405
United States
(843) 740-1200
(voice)
csc@csc.noaa.gov
Kelly Stroker
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
NOAA/NESDIS/NGDC E/GC1 325 Broadway
Boulder
CO
80305-3328
USA
(303) 497-4603
(voice)
(303) 497-6513
(fax)
kelly.stroker@noaa.gov
University Station Box X
Austin
Texas
78713
United States
Roberto: 512-471-0342
John: 512-471-4951
(voice)
512-471-0140
(fax)
Roberto: oskar@mail.utexas.edu
John: john.andrews@beg.utexas.edu
Coastal Remote Sensing Program
2234 South Hobson Avenue
Charleston
South Carolina
29405
United States
(843) 740-1200
(voice)
csc@csc.noaa.gov
Kelly Stroker
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
NOAA/NESDIS/NGDC E/GC1 325 Broadway
Boulder
CO
80305-3328
USA
(303) 497-4603
(voice)
(303) 497-6513
(fax)
kelly.stroker@noaa.gov
University Station Box X
Austin
Texas
78713
United States
Roberto: 512-471-0342
John: 512-471-4951
(voice)
512-471-0140
(fax)
Roberto: oskar@mail.utexas.edu
John: john.andrews@beg.utexas.edu
Coastal Remote Sensing Program
2234 South Hobson Avenue
Charleston
South Carolina
29405
United States
(843) 740-1200
(voice)
csc@csc.noaa.gov
Kelly Stroker
DOC/NOAA/NESDIS/NGDC > National Geophysical Data Center, NESDIS, NOAA, U.S. Department of Commerce
NOAA/NESDIS/NGDC E/GC1 325 Broadway
Boulder
CO
80305-3328
USA
(303) 497-4603
(voice)
(303) 497-6513
(fax)
kelly.stroker@noaa.gov
Hours of Service:
7:30-5:00 Mountain
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How reliable are the data; what problems remain in the data set?
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How well have the observations been checked?
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How accurate are the geographic locations?
Selected portions from each lidar data set (last return only) were used to generate a 1m x 1m digital elevation model (DEM). Data estimated to have a horizontal accuracy of 0.01-0.03m from ground surveys using kinematic GPS techniques were superimposed on the lidar DEM and examined for any mismatch between the horizontal position of the ground GPS and the corresponding feature on the lidar DEM. Horizontal agreement between the ground kinematic GPS and the lidar was within the resolution of the 1m x 1m DEM.
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How accurate are the heights or depths?
Ground GPS surveys were conducted within the lidar survey area to acquire ground "truth" information. The ground survey points are estimated to have a vertical accuracy of 0.01-0.05m. Roads, which are open areas with an unambiguous surface, were surveyed using kinematic GPS techniques. A lidar data set was sorted to find data points that fell within 0.5m of a ground GPS survey point. The mean elevation difference between the lidar and the ground GPS was used to estimate and remove an elevation bias from the lidar. The standard deviation of these elevation differences provides estimates of the lidar precision. The 2002 lidar data set was determined to have an elevation bias of 0.06m when compared to ground truth. The 0.06m bias was removed so that mean lidar elevations conform to NAVD88 with an RMSE of 0.103m.
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Where are the gaps in the data? What is missing?
Data were edited to remove outliers with ranges above of 2200m and below 100m.
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How consistent are the relationships among the observations, including topology?
Not applicable
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How can someone get a copy of the data set?
1. Are there legal restrictions on access or use of the data?
Access Constraints:
None
Use Constraints:
These data were collected for the purpose of determining amounts and rates of shoreline change along the Upper Gulf of Mexico coast of Texas following Tropical Storm Fay, September 2002. Any conclusions drawn from analysis of this information are not the responsibility of the Bureau of Economic Geology or the University of Texas at Austin or the NOAA Coastal Services Center.
2. Who distributes the data set?
Coastal Remote Sensing Program Manager
NOAA
2234 South Hobson Avenue
Charleston
SC
29405-2413
none
(voice)
(fax)
csc@csc.noaa.gov
(fax)
Kelly Stroker
DOC/NOAA/NESDIS/NGDC
NOAA/NESDIS/NGDC E/GC1 325 Broadway
Boulder
CO
80305-3328
USA
(303) 497-4603
(voice)
(303) 497-6513
(fax)
kelly.stroker@noaa.gov
(fax)
Coastal Remote Sensing Program Manager
NOAA
2234 South Hobson Avenue
Charleston
SC
29405-2413
none
(voice)
(fax)
csc@csc.noaa.gov
(fax)
Kelly Stroker
DOC/NOAA/NESDIS/NGDC
NOAA/NESDIS/NGDC E/GC1 325 Broadway
Boulder
CO
80305-3328
USA
(303) 497-4603
(voice)
(303) 497-6513
(fax)
kelly.stroker@noaa.gov
(fax)
Hours of Service:
7:30-5:00 Mountain
Contact Instructions:
Contact Data Center
3. What's the resource identifier I need to order this data set?
4. What legal disclaimers am I supposed to read?
This data was collected for the purpose of determining amounts and rates of shoreline change along the Upper Gulf of Mexico coast of Texas following Tropical Storm Fay, September 2002. Any conclusions drawn from analysis of this information are not the responsibility of the Bureau of Economic Geology or the University of Texas at Austin or the NOAA Coastal Services Center.
Disclaimer While every effort has been made to ensure that these data are accurate and reliable within the limits of the current state of the art, NOAA cannot assume liability for any damages caused by any errors or omissions in the data, nor as a result of the failure of the data to function on a particular system. NOAA makes no warranty, expressed or implied, nor does the fact of distribution constitute such a warranty.
5. How can I download or order the data?
Availability in non-digital form:
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Availability in digital form:
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6. Is there some other way to get the data?
This data can be obtained on-line at the following URL:
http://www.csc.noaa.gov/ldart.
The National Geophysical Data Center serves as the archive for this LIDAR data. NGDC should only be contacted for this data if it cannot be obtained from NOAA Coastal Services Center.
7. What hardware or software do I need in order to use the data set?
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Who wrote the metadata?
Metadata author:
Keil Schmid
NOAA Coastal Services Center
2234 South Hobson Avenue
Charleston
SC
29405-2413
none
(voice)
metadata@csc.noaa.gov
Date Last Modified
20070319
Metadata Standard
FGDC Content Standards for Digital
Geospatial Metadata
FGDC-STD-001-1998
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MISSION INFORMATION
PLATFORM INFORMATION
INSTRUMENT INFORMATION (General Overview)
1. What instruments were used to collect the data?
Instrument name not available
2. What are the instrument types? (e.g. imager, sounder, magnetometer, gps reciever, etc)
Instrument type not available
3. What are operational modes of the instruments (crosstrack, initialization, solar calibration, etc.)
Operational mode not available
4. How do the instruments collect data? (e.g. whiskbroom, laser, panoramic, etc)?
Collection type not available
5. What are the position and orientation of the instrument components on the platform?
Sensor orientation not available
INSTRUMENT INFORMATION (Sensor Specific)
