Photogrammetric digital surface models and orthoimagery of Eklutna Lake, December 5, 2018

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Frequently anticipated questions:

What does this data set describe?

Title:
Photogrammetric digital surface models and orthoimagery of Eklutna Lake, December 5, 2018
Abstract:
The State of Alaska Division of Geological & Geophysical Surveys (DGGS) produced digital surface models (DSMs) and orthorectified aerial imagery (orthoimagery) over selected locations in the greater Anchorage area following the Mw 7.1 November 30, 2018, Anchorage earthquake. We selected areas of interest (AOIs) based on initial damage reports from the Alaska Department of Transportation & Public Facilities (DOT&PF) and the United States Geological Survey (USGS) in order to document earthquake effects. Aerial photographs collected December 5-6, 2018, were processed using Structure-from-Motion (SfM) photogrammetric techniques to create sub-meter DSMs and orthoimagery. This digital data set covers Eklutna Lake and was collected on December 5, 2018. These data document ground conditions immediately following the 2018 Mw 7.1 Anchorage earthquake. For the purposes of open access to elevation and orthoimagery data sets throughout Alaska, this collection is being released as a Raw Data File with an open end-user license. The data and the data acquisition report are available from the DGGS website: https://elevation.alaska.gov/, <http://doi.org/10.14509/30274>.
Supplemental_Information: 
digital surface model: Digital surface models (DSMs) represent all observable elevations within the project extent, capturing vegetation heights, building roofs, and other opaque objects. The raster DSM products in this collection are delivered in 32-bit float format. >orthoimage: Orthoimages are aerial photographs that have been geometrically corrected (orthorectified) for spatial accuracy, coordinating surface elevation with the sensor's location throughout the survey to create a geospatial product of uniform map scale. Collected imagery is assembled into composite mosaics for delivery.
  1. How should this data set be cited?

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Eklutna Lake, December 5, 2018: Raw Data File RDF 2019-10D, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

  2. What geographic area does the data set cover?

    West_Bounding_Coordinate: -149.189645
    East_Bounding_Coordinate: -148.949915
    North_Bounding_Coordinate: 61.41473
    South_Bounding_Coordinate: 61.313337

  3. What does it look like?

  4. Does the data set describe conditions during a particular time period?

    Calendar_Date: 2018
    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: 6
      Transverse_Mercator:
      Scale_Factor_at_Central_Meridian: 0.999600
      Longitude_of_Central_Meridian: -147
      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.
      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; Geoid12A; EPOCH 2010.00
      Altitude_Resolution: 20
      Altitude_Distance_Units: meters
      Altitude_Encoding_Method: Implicit coordinate

  7. How does the data set describe geographic features?

    digital surface model
    Digital surface models (DSMs) represent all observable elevations within the project extent, capturing vegetation heights, building roofs, and other opaque objects. The raster DSM products in this collection are delivered in 32-bit float format. (Source: Alaska Division of Geological & Geophysical Surveys (DGGS))

    orthoimage
    Orthoimages are aerial photographs that have been geometrically corrected (orthorectified) for spatial accuracy, coordinating surface elevation with the sensor's location throughout the survey to create a geospatial product of uniform map scale. Collected imagery is assembled into composite mosaics for delivery. (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?

    This project was funded by State of Alaska general funds. It coincides with and augments a United States Geological Survey QL2 lidar project flown by Kodiak Mapping and available through the DGGS Elevation Portal, https://elevation.alaska.gov/#61.17636:-149.62555:9 (DGGS Staff, 2013). We thank Seth K. Kiester for assistance with equipment and logistics.

  3. To whom should users address questions about the data?

    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK 99709-3707
    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

Why was the data set created?

The data release is one of a series of Alaska Division of Geological & Geophysical Surveys (DGGS) publications that provide digital surface models (DSMs) and orthorectified aerial imagery (orthoimagery) collected over selected locations in the greater Anchorage area following the Mw 7.1 November 30, 2018, Anchorage earthquake. We selected areas of interest (AOIs) based on initial damage reports from the Alaska Department of Transportation & Public Facilities (DOT&PF) and the United States Geological Survey (USGS) in order to document ground conditions immediately following the 2018 Mw 7.1 Anchorage earthquake.

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: 2018 (process 1 of 2)
    Aircraft and instrument - Alaska DGGS and the U.S. Bureau of Land Management (BLM) collected digital aerial photographs on December 5-6, 2018, from a fixed-wing (Cessna 180) airborne platform. Photographic survey plans included 60 percent side-lap and 80 percent end-lap coverage at variable above ground-level (AGL) heights, dependent upon the size/shapes of the AOIs and atmospheric conditions. We collected 7,238 photographs, covering 130 square kilometers with ground sample distances (GSDs) ranging from 3.6-22.8 cm. We used a Nikon D850 with an AF-Nikkor 24 mm lens to collect 45.4 Megapixel (8,256 x 5,504 pixels per image), 14-bit NEF.RAW (processed in Adobe Lightroom to 48-bit uncompressed TIFF photographs) and fine JPEGS. The aerial survey was controlled with an automatic flight control system and Aviatrix software, linking the camera shutter release with Global Navigation Satellite System (GNSS), Trimble R7 receiver, and a dual-band Novatel antenna mounted 0.96 m above the camera sensor.

    Date: 2018 (process 2 of 2)
    SFM data processing - An equipment malfunction during collection compromised sensor location data for each image. Because the camera shutter maintained synchronicity with GNSS input, surveyed data remained suitable for further processing with additional steps required. We processed and calibrated data from each of the 14 AOIs separately in Agisoft Metashape (Version 1.5.2 build 7838), beginning with photograph alignment and calibration of camera positions. We integrated ground control points (GCPs) in these initial procedures to achieve accurate georeferencing for all subsequent data products. Structure-from-Motion (SfM) processing continued with the construction of point clouds and surface models. Photographs were orthorectified using relative camera positions in conjunction with GCP-controlled surface models. The results were analyzed for quality control using additional checkpoints.

  3. What similar or related data should the user be aware of?

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, November 30, 2018, Mw 7.1 Anchorage earthquake photogrammetry: Raw Data File RDF 2019-10, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Ted Stevens Anchorage International Airport, December 6, 2018: Raw Data File RDF 2019-10A, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Campbell Lake Dam, December 5, 2018: Raw Data File RDF 2019-10B, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of EauClaire Place, December 5, 2018: Raw Data File RDF 2019-10C, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Glenn Highway, December 5, 2018: Raw Data File RDF 2019-10E, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Lake O the Hills neighborhood, December 5, 2018: Raw Data File RDF 2019-10F, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Mackenzie Road, December 5, 2018: Raw Data File RDF 2019-10G, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Minnesota Drive, December 5, 2018: Raw Data File RDF 2019-10H, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Pittman Road, December 5, 2018: Raw Data File RDF 2019-10I, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Potter Creek, December 6, 2018: Raw Data File RDF 2019-10J, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Seward Highway, December 6, 2018: Raw Data File RDF 2019-10K, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Ship Creek Dam, December 5, 2018: Raw Data File RDF 2019-10L, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Vine Road, December 5, 2018: Raw Data File RDF 2019-10M, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

    Salisbury, J.B., Herbst, A.M., and Wikstrom Jones, Katreen, 2019, Photogrammetric digital surface models and orthoimagery of Westchester Lagoon, December 5, 2018: Raw Data File RDF 2019-10N, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.

    Online Links:

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

  1. How well have the observations been checked?

    We evaluated data quality based on vertical and horizontal accuracy compared to control data. See accompanying data acquisition report for a comprehensive listing of control points, checkpoints, accuracy statistics, and known anomalies.

  2. How accurate are the geographic locations?

    Due to the size and scale of the study area, conventional ground control methods were unobtainable within the timeframe of the survey. Instead, we extracted photo-identifiable horizontal ground control from Earth Systems Research Institute's (ESRI) orthoimagery map service (World Imagery [Clarity], https://www.arcgis.com/home/item.html?id=ab399b847323487dba26809bf11ea91a). The ESRI image service provided accuracies of 0.45 m-1 m.

  3. How accurate are the heights or depths?

    We used a 2015 lidar survey for the Municipality of Anchorage, Alaska for vertical control on those same points. The 2015 Anchorage lidar data provide a vertical accuracy of 7.2 cm and are available through the DGGS Elevation Portal, https://elevation.alaska.gov/#61.17636:-149.62555:9

  4. Where are the gaps in the data? What is missing?

    Data voids may be observed in the orthophotos. These gaps are a result from the orthorectification process, where pixels where spatially adjusted and the formerly occupied area was not interpolated. Because vertical elevation control is based on a 2015 lidar survey, these data are not suitable for calculating regional-scale vertical ground surface deformation.

  5. How consistent are the relationships among the observations, including topology?

    We evaluated data quality based on vertical and horizontal accuracy compared to control data. Root mean square errors (RMSE) are reported in the accompanying acquisition report.

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)

    Alaska Division of Geological & Geophysical Surveys
    Metadata Manager
    3354 College Road
    Fairbanks, AK 99709-3707
    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
  2. What's the catalog number I need to order this data set?

    RDF 2019-10D

  3. What legal disclaimers am I supposed to read?

    The State of Alaska makes no expressed 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.

  4. How can I download or order the data?

Who wrote the metadata?

Dates:
Last modified: 30-Dec-2019
Metadata author:
Alaska Division of Geological & Geophysical Surveys
Attn: Simone Montayne
Metadata Manager
3354 College Road
Fairbanks, AK 99709-3707
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
Metadata standard:
FGDC Content Standard for Digital Geospatial Metadata (FGDC-STD-001-1998)
Metadata extensions used:

Generated by mp version 2.9.21 on Thu Jan 16 12:00:16 2020