ATM Coastal Topography--Texas, 2001: UTM Zone 15

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Frequently anticipated questions:

What does this data set describe?

Title: ATM Coastal Topography--Texas, 2001: UTM Zone 15
A first-surface elevation map was produced cooperatively from remotely sensed, geographically referenced elevation measurements by the U.S. Geological Survey (USGS) and National Aeronautics and Space Administration (NASA). Elevation measurements were collected over the area using the NASA Airborne Topographic Mapper (ATM), a scanning lidar system that measures high-resolution topography of the land surface. The ATM system is deployed on a Twin Otter or P-3 Orion aircraft and incorporates a green-wavelength laser operating at pulse rates of 2 to 10 kilohertz. Measurements from the laser-ranging device are coupled with data acquired from inertial navigation system (INS) attitude sensors and differentially corrected global positioning system (GPS) receivers to measure topography of the surface at accuracies of +/-15 centimeters.
For more information on Lidar science and the Experimental Advanced Airborne Research Lidar (EAARL) system and surveys, see and .
Raw lidar data are not in a format that is generally usable by resource managers and scientists. Converting dense lidar elevation data into a readily usable format without loss of essential information requires specialized processing. The U.S. Geological Survey's Coastal and Marine Geology Program (CMGP) has developed custom software to convert raw lidar data into a GIS-compatible map product to be provided to GIS specialists, managers, and scientists. The primary tool used in the conversion process is Advanced Lidar Processing System (ALPS), a multi-tiered processing system developed by a USGS-NASA collaborative project. The zero crossing of the second derivative (that is, detection of local maxima) is used to detect "first surface" topography. Statistical filtering, known as the Random Consensus Filter (RCF), is used to remove false bottom returns and other outliers from the ATM topography data. The filter uses a grid of non-overlapping square cells (buffer) of user-defined size overlaid onto the original point cloud. The user also defines the vertical tolerance (vertical width) based on the topographic complexity and point sampling density of the data. The maximum allowable elevation range within a cell is established by this vertical tolerance. An iterative process searches for the maximum concentration of points within the vertical tolerance, and removes those points outside of the tolerance (Nayegandhi and others, 2009). These data are converted to the North American Datum of 1983 and the North American Vertical Datum of 1988 (using the GEOID03 model). The files are in the Quarter-Quad tiling format, and the exact tile location is contained in the filename at ########_fs, where ####### is the Quarter-Quad tile ID.The development of custom software for creating these data products has been supported by the USGS CMG Program's Decision Support for Coastal Parks, Sanctuaries, and Preserves Project. Processed data products are used by the USGS CMG Program's National Assessments of Coastal Change Hazards Project to quantify the vulnerability of shorelines to coastal change hazards such as severe storms, sea-level rise, and shoreline erosion and retreat.
  1. How might this data set be cited?
    U.S. Geological Survey, 2009, ATM Coastal Topography--Texas, 2001: UTM Zone 15: U.S. Geological Survey Data Series 449, U.S. Geological Survey, St. Petersburg, FL.

    Online Links:

  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -96
    East_Bounding_Coordinate: -94.5
    North_Bounding_Coordinate: 29.5
    South_Bounding_Coordinate: 28.5
  3. What does it look like? (JPG)
    ATM Coastal Topography–Texas, 2001: UTM Zone 15
  4. Does the data set describe conditions during a particular time period?
    Calendar_Date: 12-Oct-2001
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: remote-sensing image
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      Indirect_Spatial_Reference: Quater-Quadrangle
      This is a Raster data set. It contains the following raster data types:
      • Dimensions, type Pixel
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      UTM_Zone_Number: 15
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -93.000000
      Latitude_of_Projection_Origin: 0.000000
      False_Easting: 500000.000000
      False_Northing: 0.000000
      Planar coordinates are encoded using row and column
      Abscissae (x-coordinates) are specified to the nearest 4.000000
      Ordinates (y-coordinates) are specified to the nearest 4.000000
      Planar coordinates are specified in meters
      The horizontal datum used is North American Datum of 1983.
      The ellipsoid used is Geodetic Reference System 80.
      The semi-major axis of the ellipsoid used is 6378137.000000.
      The flattening of the ellipsoid used is 1/298.257222.
      Altitude_Datum_Name: North American Vertical Datum of 1988
      Altitude_Resolution: 0.15 meters
      Altitude_Distance_Units: meters
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    This Digital Elevation Model is a GeoTIFF. It is raster data consisting of cells. Each cell has an elevation value associated with it. The input parameters for the Random Consensus Filter (RCF) were grid cell size/buffer (25 meters by 25 meters) and vertical tolerance/vertical width (12 meters).
    The variables measured by ATM are distance between aircraft and GPS satellites (meters), attitude information (roll, pitch, heading in degrees), scan angle (degrees), second of the epoch (seconds), and 1-nanosecond time-resolved return intensity waveform (digital counts). Z value is referenced to orthometric elevations derived from National Geodetic Survey Geoid Model, GEOID03.

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
    • U.S. Geological Survey
  2. Who also contributed to the data set?
    Acknowledgment of the U.S. Geological Survey, Florida Integrated Science Center, as a data source would be appreciated in products developed from these data, and such acknowledgment as is standard for citation and legal practices for data source is expected. Sharing of new data layers developed directly from these data would also be appreciated by the U.S. Geological Survey staff. Users should be aware that comparisons with other datasets for the same area from other time periods may be inaccurate due to inconsistencies resulting from changes in photointerpretation, mapping conventions, and digital processes over time. These data are not legal documents and are not to be used as such.
  3. To whom should users address questions about the data?
    Amar Nayegandhi
    Jacobs Technology, U.S. Geological Survey, FISC
    Computer Scientist
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 (x3026) (voice)
    Hours_of_Service: M-F, 8:00-5:00 EST

Why was the data set created?

The purpose of this project is to produce highly detailed and accurate elevation maps of a portion of the Texas coastline within UTM zone 15 for natural-resource managers and research scientists.

How was the data set created?

  1. From what previous works were the data drawn?
  2. How were the data generated, processed, and modified?
    Date: 04-Feb-2009 (process 1 of 4)
    The data are collected using a Twin Otter aircraft. The NASA Airborne Topographic Mapper (ATM) laser scanner collects the data using a green-wavelength raster scanning laser. The data are stored on hard drives and archived at the U.S. Geological Survey's FISC office in St. Petersburg, FL, and the NASA office at Wallops Flight Facility in Virginia. The navigational data are processed at Wallops Flight Facility. The navigational and raw data are then downloaded into the Advanced Lidar Processing System (ALPS). Data are converted from units of time to x,y,z points for elevation. The derived surface data can then be converted into raster data (GeoTIFFs). Person who carried out this activity:
    Amar Nayegandhi
    Jacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FL
    Computer Scientist
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 (x3026) (voice)
    Hours_of_Service: M-F, 8:00-5:00 EST
    Date: 04-Feb-2009 (process 2 of 4)
    Metadata imported into ArcCatalog from XML file. Person who carried out this activity:
    Xan Yates
    Jacobs Technology, U.S. Geological Survey, FISC, St. Petersburg, FL
    GIS/Image Analyst/Metadata Specialist
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 (x3086) (voice)
    Hours_of_Service: M-F, 9:00-5:30 EST
    Date: 24-Jan-2017 (process 3 of 4)
    Keywords section of metadata optimized for discovery in USGS Coastal and Marine Geology Data Catalog. Person who carried out this activity:
    U.S. Geological Survey
    Attn: Alan O. Allwardt
    Contractor -- Information Specialist
    2885 Mission Street
    Santa Cruz, CA

    831-460-7551 (voice)
    831-427-4748 (FAX)
    Date: 13-Oct-2020 (process 4 of 4)
    Added keywords section with USGS persistent identifier as theme keyword. Person who carried out this activity:
    U.S. Geological Survey
    Attn: VeeAnn A. Cross
    Marine Geologist
    384 Woods Hole Road
    Woods Hole, MA

    508-548-8700 x2251 (voice)
    508-457-2310 (FAX)
  3. What similar or related data should the user be aware of?

How reliable are the data; what problems remain in the data set?

  1. How well have the observations been checked?
    The expected accuracy of the measured variables is as follows: attitude within 0.07 degree, 3-centimeter nominal laser ranging accuracy, and vertical elevation accuracy of +/-15 centimeters for the topographic surface. Quality checks are built into the data-processing software.
  2. How accurate are the geographic locations?
    Raw elevation measurements have been determined to be within 1 meter in horizontal accuracy.
  3. How accurate are the heights or depths?
    Elevations of the DEM are vertically consistent with the point elevation data, +/-15 centimeters.
  4. Where are the gaps in the data? What is missing?
    Several regions of the dataset are labeled as "No Data," which corresponds to a cell value of -32767 meters in the GeoTIFF file. These "No Data" areas are a result of the survey not covering a particular region, optical water depth of greater than 1.5 Secchi disc depths, or the manual removal of lidar processing artifacts. Please note that this metadata file is a sample and therefore does not include valid bounding coordinates.
  5. How consistent are the relationships among the observations, including topology?
    The files are in the Quarter-Quad tiling format, and the exact tile location is contained in the filename at ########_fs, where ####### is the Quarter-Quad tile ID.See the DOQQ naming convention document in the 'extras' directory.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints: None
The U.S. Geological Survey and National Aeronautics and Space Administration request to be acknowledged as originators of the dataset in future products or derivative research.
  1. Who distributes the data set? (Distributor 1 of 1)
    U.S. Geological Survey
    Attn: Project Manager
    Project Manager
    600 4th Street South
    St. Petersburg, FL

    727-803-8747 (x3026) (voice)
    Hours_of_Service: M-F, 8:00-5:00 EST
  2. What's the catalog number I need to order this data set? DS 449
  3. What legal disclaimers am I supposed to read?
    This DVD publication was prepared by an agency of the United States Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey, no warranty expressed or implied is made regarding the display or utility of the data on any other system, nor shall the act of distribution imply any such warranty. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data described and (or) contained herein. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof.
  4. How can I download or order the data?
    • Availability in digital form:
      Data format: TIFF (version 2) GeoTIFF
      Network links:
      Media you can order: DVD (format DVD)
    • Cost to order the data: Vary

    • Special instructions:
      Contact U.S. Geological Survey
    • How long will it take to get the data?
  5. Is there some other way to get the data?
    Contact U.S. Geological Survey for details.

Who wrote the metadata?

Last modified: 09-Nov-2021
Metadata author:
United States Geological Survey, St. Petersburg Coastal and Marine Science Center
Attn: SPCMSC Data Management Group
600 4th Street South
St. Petersburg, Florida

727-502-8000 (voice)
Metadata standard:
Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)

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