High-resolution lidar data for Kotlik, Western Alaska

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Frequently anticipated questions:


What does this data set describe?

Title: High-resolution lidar data for Kotlik, Western Alaska
Abstract:
The Alaska Division of Geological & Geophysical Surveys (DGGS) used aerial lidar to produce a digital terrain model (DTM), surface model (DSM), and intensity model for the area surrounding the community of Kotlik, Alaska. Detailed bare earth elevation data for the Kotlik area support and inform potential infrastructure development and provide critical information required to assess geomorphic activity. Airborne data were collected on August 17, 2019, and subsequently processed in Terrasolid and ArcGIS. Ground control was collected between August 20-22, 2019, by the Alaska Division of Mining, Land, and Water. This data collection is released as a Raw Data File with an open end-user license. All files can be downloaded free of charge from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/30561).
Supplemental_Information:
classified point cloud data: Classified point cloud data is provided in this collection in compressed .laz format. Data are classified in accordance with ASPRS 2014 guidelines and contain return and intensity information. The average pulse spacing was 24.8 cm and the average density was 16.25 pts/m^2. Elevation surfaces interpolated from areas with a point density of fewer than 4pts/m2 were classified as nodata. 
digital surface model: The DSM represents surface elevations, for example, heights of vegetation, buildings, bridges, etc. The DSM is a single band, 32-bit GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038. 
digital terrain model: The DTM represents surface elevations of ground surfaces, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038. 
lidar intensity image: The lidar intensity image describes the relative amplitude of reflected signals, contributing to the point cloud. Lidar intensity is largely a function of scanned object reflectance in relation to the signal frequency, is dependent on ambient conditions, and is not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit float GeoTIFF file with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038 (32-bit, floating-point minimum). 
hydro-enforced digital terrain model: The hydro-enforced DTM represents bare earth surfaces which have undergone a selective "flattening" process, where elevation values for any hydrologic features, as well as any hydrologic obstacles (bridges, culverts, etc.), are replaced with neighboring pixel values. The hydro-enforced DTM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038.
  1. How might this data set be cited?
    Herbst, A.M., and Daanen, R.D., 2020, High-resolution lidar data for Kotlik, Western Alaska: Raw Data File RDF 2020-15, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Other_Citation_Details: 7 p
  2. What geographic area does the data set cover?
    West_Bounding_Coordinate: -163.659031
    East_Bounding_Coordinate: -163.005119
    North_Bounding_Coordinate: 63.111833
    South_Bounding_Coordinate: 62.986807
  3. What does it look like?
  4. Does the data set describe conditions during a particular time period?
    Beginning_Date: 17-Aug-2019
    Ending_Date: 22-Aug-2019
    Currentness_Reference:
    ground condition
  5. What is the general form of this data set?
    Geospatial_Data_Presentation_Form: imagery
  6. How does the data set represent geographic features?
    1. How are geographic features stored in the data set?
      This is a raster data set.
    2. What coordinate system is used to represent geographic features?
      Grid_Coordinate_System_Name: Universal Transverse Mercator
      Universal_Transverse_Mercator:
      UTM_Zone_Number: 3
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -165
      Latitude_of_Projection_Origin: 0
      False_Easting: 500000.000000
      False_Northing: 0
      Planar coordinates are encoded using coordinate pair
      Abscissae (x-coordinates) are specified to the nearest .00000001
      Ordinates (y-coordinates) are specified to the nearest .00000001
      Planar coordinates are specified in Meters
      The horizontal datum used is North American Datum of 1983 (CORS96).
      The ellipsoid used is GRS 80.
      The semi-major axis of the ellipsoid used is 6378137.
      The flattening of the ellipsoid used is 1/298.257222101000025.
      Vertical_Coordinate_System_Definition:
      Altitude_System_Definition:
      Altitude_Datum_Name: NAVD88, GEOID12B
      Altitude_Resolution: 0.5
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method:
      Explicit elevation coordinate included with horizontal coordinates
  7. How does the data set describe geographic features?
    classified point cloud data
    Classified point cloud data is provided in this collection in compressed .laz format. Data are classified in accordance with ASPRS 2014 guidelines and contain return and intensity information. The average pulse spacing was 24.8 cm and the average density was 16.25 pts/m^2. Elevation surfaces interpolated from areas with a point density of fewer than 4pts/m2 were classified as nodata. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    digital surface model
    The DSM represents surface elevations, for example, heights of vegetation, buildings, bridges, etc. The DSM is a single band, 32-bit GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    digital terrain model
    The DTM represents surface elevations of ground surfaces, excluding vegetation, bridges, buildings, etc. The DTM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    lidar intensity image
    The lidar intensity image describes the relative amplitude of reflected signals, contributing to the point cloud. Lidar intensity is largely a function of scanned object reflectance in relation to the signal frequency, is dependent on ambient conditions, and is not necessarily consistent between separate scans. The intensity image is a single-band, 32-bit float GeoTIFF file with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038 (32-bit, floating-point minimum). (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))
    hydro-enforced digital terrain model
    The hydro-enforced DTM represents bare earth surfaces which have undergone a selective "flattening" process, where elevation values for any hydrologic features, as well as any hydrologic obstacles (bridges, culverts, etc.), are replaced with neighboring pixel values. The hydro-enforced DTM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance of 0.5 meters. No Data value is set to -3.40282306074e+038. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

Who produced the data set?

  1. Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
  2. Who also contributed to the data set?
    These data were paid for by the State of Alaska and collected and processed by DGGS. A ground survey was conducted for quality control by the Alaska Division of Mining, Land and Water, and supported by the Native Village of Bill Moore's Slough and the Native Village of Kotlik.
  3. To whom should users address questions about the data?
    Alaska Division of Geological & Geophysical Surveys
    GIS Manager
    3354 College Rd
    Fairbanks, AK
    USA

    907-451-5020 (voice)
    dggsgis@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays

Why was the data set created?

Detailed bare earth elevation data for the Kotlik area support and inform potential infrastructure development and provide critical information required to assess geomorphic activity. This data release is one of a series of DGGS publications to present elevation data.

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: 17-Aug-2019 (process 1 of 3)
    Airborne survey - DGGS operates a Riegl VUX1-LR lidar integrated with a GNSS and Northrop Grumman IMU system. The integration was designed by Phoenix LiDAR systems. The sensor is capable of collecting up to 820,000 points per second over a distance of 150 m. This survey was flown at a scan rate between 200,000 and 400,000 points per second at a scan rate between 80 and 150 lines per second. This survey was flown with an average elevation of 400 m above ground level and a ground speed of approximately 40 m/s with a fixed-wing aircraft configuration, using a Cessna 185 aircraft. The scan angle was set from 55 to 305 degrees. The total area surveyed was approximately 15 km2. The accompanying report provides additional detail regarding flight conditions.
    Date: 22-Aug-2019 (process 2 of 3)
    Ground survey - Licensed surveyors from the Alaska Division of Mining, Land and Water acquired surveyed ground control August 20-22, 2019 in an approximate 2-mile radius around the town of Kotlik. Ninety-four points were collected, including 42 bare earth, 18 forested, 33 low-vegetation, and 1 urban surface points.
    Date: 2020 (process 3 of 3)
    Lidar dataset processing - Point data were processed in SDCimport software for initial filtering and multiple-time-around (MTA) disambiguation. MTA errors, corrected in this process, are the result of imprecise interpretations of received pulse time intervals and occur more frequently with higher pulse refresh rates. IMU and GPS data were used to integrate flightline information with the point cloud in Spatial Explorer software. The point data were calibrated at an incrementally precise scale of sensor movement and behavior, incorporating sensor velocity, roll, pitch, and yaw fluctuations throughout the survey. Points were classified in accordance with ASPRS 2014 guidelines, using macros designed in Terrasolid software. Careful attention was given to the interpolation of the project's ground surface to compensate for inconsistent penetration through low vegetation as a function of the scan angle. Once classified, points underwent a geometric transformation and were converted from ellipsoidal heights to GEOID12B (Alaska) heights. Raster products were derived from the point cloud, using ArcMap. The DTM was interpolated from all ground class returns using a tin-based method. The DTM was also used to produce a separate hydroflattened raster, incorporating hydrography polygons from the AK SDMI IFSAR dataset. The DSM was likewise interpolated from only the first returns for all classes. An intensity image was also produced in ArcMap, using closest-to-mean binning.
  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?
    Not applicable
  2. How accurate are the geographic locations?
    Horizontal accuracy was not measured for this collection.
  3. How accurate are the heights or depths?
    Forty-two bare earth checkpoints were used to determine the non-vegetated vertical accuracy (NVA) of the point cloud ground class, using a tin-based approach. Project NVA was calculated to have a root mean square error (RMSE) of 8.2 cm. Using the same approach, fifty-two vegetated points were used to determine the vegetated vertical accuracy (VVA) of the point cloud ground class. Project VVA was evaluated at 25.2 cm RMSE, with an average elevation difference of +21.2 cm.
  4. Where are the gaps in the data? What is missing?
    This data release is complete, and there is no over collect except for the aircraft turns that were eliminated from the dataset.
  5. How consistent are the relationships among the observations, including topology?
    The data quality is consistent throughout the survey. The accompanying report provides additional detail regarding tests used to determine data fidelity.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?
Access_Constraints:
This report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).
Use_Constraints:
Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.
  1. Who distributes the data set? (Distributor 1 of 1)
    State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys
    Attn: Simone Montayne
    3354 College Road
    Fairbanks, AK
    USA

    907-451-5020 (voice)
    907-451-5050 (FAX)
    dggspubs@alaska.gov
    Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays
    Contact_Instructions:
    Please view our website (http://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.
  2. What's the catalog number I need to order this data set? RDF 2020-15
  3. What legal disclaimers am I supposed to read?
    The State of Alaska makes no express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity, whether from the use of the electronic services or products, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requestor or anyone else exceed the fee paid for the electronic service or product.
  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 13-Nov-2020
Metadata author:
Simone Montayne
3354 College Road
Fairbanks, AK
USA

907-451-5020 (voice)
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.50 on Mon Dec 28 18:32:58 2020