Photogrammetry-derived orthoimagery and elevation data for Kivalina, Alaska, collected June 7, 2922

Horen, K.C. Siemsen, Z.J. 2022 Photogrammetry-derived orthoimagery and elevation data for Kivalina, Alaska, collected June 7, 2922 data Raw Data File RDF 2022-12 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 5 p. https://doi.org/10.14509/30902 Photogrammetry-derived orthoimagery and elevation data for Kivalina, Alaska, collected June 7, 2922, Raw Data File 2022-12, uses low-altitude aerial images, collected from an unmanned aerial vehicle (UAV) on June 7, 2022, and Structure-from-Motion (SfM) photogrammetry to produce a digital surface model (DSM) and orthoimagery for the community of Kivalina, Alaska. The orthoimage and elevation data are for assessing coastal hazards and changes. We used Trimble Business Center to process the Global Navigation Satellite System (GNSS) data used for positional control and NOAA VDatum to adjust elevation data. We used Agisoft Metashape to process photogrammetry data. These products are released as a Raw Data File with an open end-user license. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/30902). The orthoimage and elevation data were collected for assessing coastal hazards and changes. >digital surface model: The DSM represents surface elevations such as the height of vegetation and buildings. We filtered the dense cloud to remove low confidence points with less than three contributing image renderings containing distance information. Since water bodies can introduce noise, we manually delineated the beach boundaries to restrict the DSM to land only. Boundaries were identified using both visual selection from collected aerial images and point confidence. The DSM is a single-band, 32-bit floating point GeoTIFF file with a GSD of 0.031 m. The No Data value is set to -3.4028231 x 10^38. >orthoimagery: The orthoimage is a three-band (red, green, blue), 8-bit unsigned GeoTIFF file with a GSD of 0.016 m per pixel; the No Data value is set to 256. 20220722 ground condition complete None planned -164.550548 -164.524463 67.731827 67.722733 ISO 19115 Topic Category geoscientificInformation Alaska Division of Geological & Geophysical Surveys Aerial Aerial Geology Aerial Photography Coastal Coastal Erosion Coastal Plain Coastal and River Coastal and River Hazards DGGS Digital Surface Model (DSM) Elevation Emergency Preparedness Environmental Erosion Flood Floodplain Geologic Geologic Hazards Geology Geomorphology Geotechnical Hazards Photogrammetry Raster Image Remote Sensing Sea Level Changes Shoreface Surface Surface Water Surficial Surficial Geology Alaska Division of Geological & Geophysical Surveys Eagle Creek Echo Creek First Lake Justice Creek Kivalina Portage Creek Steelhead Creek Topsy Creek 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). 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. Alaska Division of Geological & Geophysical Surveys Metadata Manager mailing and physical

3354 College Road

Fairbanks AK 99709-3707 USA (907)451-5020 (907)451-5050 dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays Please view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible. These data products were funded by the National Coastal Resilience Fund. We thank the City and Native Village of Kivalina for supporting the creation of these data products. Buzard, R.M. Overbeck, J.R. Maio, C.V. 2019 Community-based methods for monitoring coastal erosion Information Circular IC 84 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 35 p https://doi.org/10.14509/30182 Overbeck, J.R. 2018 Coastal flooding & erosion in Alaska Information Circular IC 68 Fairbanks, Alaska, United States Alaska Division of Geological & Geophysical Surveys 2 p https://doi.org/10.14509/30057 Not applicable DGGS visually inspected the orthoimage for data errors such as shifts, seamline mismatches, and water noise overlapping land. There were no significantly erroneous areas that required repair. Visual errors common to these SfM photogrammetry products include discontinuous powerlines, blurriness near high-angle features like buildings, and distortion at water boundaries. Bright objects like metal roofs and white paint can cause overexposure, leading to spurious elevation points. This data relaease is complete. We quantify the horizontal accuracy of the DSM and orthoimage by comparing the known locations of eight photo-identifiable check points measured with GNSS against their modeled locations in the photogrammetric products. These are independent checkpoints not used in processing. X and Y errors are calculated as the root-mean-square (RMS) error of offsets. The total horizontal error is the root-sum-square error of X and Y RMS errors, 0.042 m. See accompanying report for a table of checkpoints and further discussion of factors impacting the certainty of data locations. We assess the vertical accuracy of the DSM using the same check points. The RMS error of Z offsets is 0.066 m. The total error of the DSM (X, Y, and Z) is 0.078 m. See the accompanying report for check points and additional detail. Aerial photogrammetric survey - DGGS used a DJI Phantom 4 RTK UAV with a FC6310R camera model (8.8 mm lens) to collect 20-megapixel JPEG photographs (5472 x 3648 pixels per image). We flew the aerial survey with 70 percent sidelap and 80 percent frontlap, 91 m above ground-level at 6.5 m/s, with nadir orientation stabilized using a 3-axis gimbal. This resulted in images covering 0.56 km2 with ground sampling distance (GSD) of 0.016 m. DGGS conducted flights on June 7, 2022, from approximately 7:45 PM to 8:30 PM AKDT. The operator returned the UAV two times to change batteries. The weather throughout the survey was clear with light wind. No abnormalities were observed during the flights. 20220722 Ground survey - DGGS set up a GNSS base station using the Trimble R10 receiver sampling at 5 Hz. The base was installed over known benchmark KVL A with a published solution (found at https://www.ngs.noaa.gov/cgi-bin/ds_mark.prl?PidBox=DN5562). This provided real-time kinematic (RTK) corrections to the Trimble R8s GNSS receiver (ground rover). The corrected base position was derived using the Canadian Spatial Reference System Precision Point Positioning (CSRS-PPP) service (found at https://webapp.csrs-scrs.nrcan-rncan.gc.ca/geod/tools-outils/ppp.php). The R8s' positions were updated using post-processed kinematic (PPK) corrections in Trimble Business Center. DGGS measured 19 photo-identifiable ground control points (GCPs) with the ground rover, 11 of which were utilized for georeferencing during processing. The remaining eight were reserved for quality control checks. 2022 Photogrammetric dataset processing - During the survey, the UAV maintained RTK connection. Within the UAV GNSS receiver settings, the lever arm correction is automatically applied and camera GNSS coordinates are written to the image metadata in WGS84 ellipsoid. Yaw, pitch, and roll information are not written to the image metadata. During processing we update UAV positions using an X, Y, and Z shift from the initial to corrected base position. DGGS processed using Agisoft Metashape Professional software (Version 1.6.3 build 10732). We masked image corners where shadows and image warping were disruptive. Processing steps included aligning images, identifying GCPs, manually cleaning sparse point cloud, optimizing the bundle block adjustment (refining camera position and lens distortion parameters), constructing the dense point cloud, building the DSM, and creating the orthomosaic image. During processing, we used 11 GCPs to create the model, leaving eight GCPs as horizontal and vertical check points. 2022 raster Universal Transverse Mercator 3 0.999600 -165 0 500000.000000 0 coordinate pair .00000001 .00000001 Meters NAD83 (2011) GRS 80 6378137 298.257222101 NAVD88, GEOID12B 0.001 meters Explicit elevation coordinate included with horizontal coordinates digital surface model The DSM represents surface elevations such as the height of vegetation and buildings. We filtered the dense cloud to remove low confidence points with less than three contributing image renderings containing distance information. Since water bodies can introduce noise, we manually delineated the beach boundaries to restrict the DSM to land only. Boundaries were identified using both visual selection from collected aerial images and point confidence. The DSM is a single-band, 32-bit floating point GeoTIFF file with a GSD of 0.031 m. The No Data value is set to -3.4028231 x 10^38. DGGS digital surface model orthoimagery The orthoimage is a three-band (red, green, blue), 8-bit unsigned GeoTIFF file with a GSD of 0.016 m per pixel; the No Data value is set to 256. DGGS orthoimagery Alaska Division of Geological & Geophysical Surveys Metadata Manager mailing and physical

3354 College Road

Fairbanks AK 99709-3707 USA (907)451-5020 (907)451-5050 dggspubs@alaska.gov 8 am to 4:30 pm, Monday through Friday, except State holidays FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the Alaska Department of Natural Resources or Division of Geological & Geophysical Surveys. https://dggs.alaska.gov/metadata/dggs.ext dggs metadata extensions