Photogrammetry-derived orthoimagery and elevation data for Saint Michael, Alaska, collected July 8, 2022

Horen, K.C.Brayton, C.E.Christian, J.E.Overbeck, J.R.Poisson, A.C.Siemsen, Z.J.2024Photogrammetry-derived orthoimagery and elevation data for Saint Michael, Alaska, collected July 8, 2022dataRaw Data FileRDF 2024-22Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys6 p.https://doi.org/10.14509/31290Photogrammetry-derived orthoimagery and elevation data for Saint Michael, Alaska, collected July 8, 2022, Raw Data File 2024-22, provides low-altitude aerial images from an unmanned aerial vehicle (UAV) in the community of Saint Michael, Alaska, on July 8, 2022. We used Structure-from-Motion (SfM) photogrammetry to produce a digital surface model (DSM) and orthoimagery. The orthoimage and elevation data are useful for assessing riverine hazards and changes over time. All files can be downloaded from the Alaska Division of Geological & Geophysical Surveys website (http://doi.org/10.14509/31290).The orthoimage and elevation data are useful for assessing riverine hazards and changes over time.>boundaries: A boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data. Also includes footprints for tiled data. >dsm: The DSM represents surface elevations including the height of vegetation, buildings, and other man-made features derived from the dense point cloud. The DSM is a single-band, 32-bit floating point GeoTIFF file with a GSD of 0.071 m; the No Data value is set to -3.4028235e+38. >ortho_rgb: The orthoimage is a three-band (red, green, blue), eight-bit unsigned GeoTIFF file derived from a color-adjusted mosaic of 1,864 aerial photographs with a GSD of 0.024 m per pixel; the No Data value is set to 0.20220708ground conditioncompleteNone planned-162.068852-162.00185663.49465463.468338ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical SurveysCoastalCoastal ErosionCoastal PlainCoastal and RiverDGGSDigital Elevation ModelDigital Surface Model (DSM)ElevationEmergency PreparednessEngineeringEngineering GeologyFloodFloodplainGeologicGeologic HazardsGeological ProcessGeologyGeomorphologyGeophysicsGeotechnicalHazardsRaster ImageRemote SensingSurfaceSurficialSurficial GeologyTopographyAlaska Division of Geological & Geophysical SurveysNorton SoundSaint MichaelThis 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 SurveysMetadata Managermailing and physical

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FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysPlease 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.We thank the Native Village and City of Saint Michael for supporting the creation of these data products, made possible with National Fish and Wildlife Foundation's National Coastal Resilience Funding through our partners at the Alaska Native Tribal Health Consortium. The views and conclusions contained in this document are those of the authors and should not be interpreted as representing the opinions or policies of the Alaska Division of Geological & Geophysical Surveys, the U.S. Government, or the National Fish and Wildlife Foundation and its funding sources. Mention of trade names or commercial products does not constitute their endorsement by the Alaska Division of Geological & Geophysical Surveys, the U.S. Government, or the National Fish and Wildlife Foundation and its funding sources.Horen, K.C.Brayton, C.E.Christian, J.E.Overbeck, J.R.Poisson, A.C.Siemsen, Z.J.2023Single-beam bathymetric data near Saint Michael, Alaska, collected July 8-9, 2022Raw Data FileRDF 2023-8Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys8 phttps://doi.org/10.14509/31006Not applicableDGGS visually inspected the orthoimage for data errors such as shifts, seamline mismatches, and water noise overlapping land. Visual errors common to these SfM photogrammetry products include discontinuous powerlines and distortion near high-angle features like buildings, as well as water boundaries. Highly reflective objects such as water bodies, metal roofs, and white paint may cause overexposure, leading to spurious elevation points. There were no significantly erroneous areas that required repair.This is a full-release dataset.DGGS quantified the horizontal accuracy of the GNSS position data using the latitudinal and longitudinal peak-to-peak errors provided by OPUS. Consistent with OPUS shared solution requirements (NOAA, 2022), DGGS considers high-quality GNSS solutions to have latitudinal and longitudinal errors less than or equal to 0.04 m. We quantified the horizontal accuracy of the DSM and orthoimage by comparing the known locations of 12 photo-identifiable check points measured with GNSS against their modeled locations in the photogrammetric products. These are independent checkpoints not used during processing. X and Y errors are calculated as the root-mean-square (RMS) error of offsets, 0.032 m and 0.033 m, respectively. The total horizontal error is the root-sum-square error of X and Y RMS errors, 0.046 m.DGGS quantified the vertical accuracy of the GNSS position data using the combined ellipsoidal height peak-to-peak errors provided by OPUS and orthometric height RMS error provided by NOAA's Vertical Datum Transformation software (NOAA, 2016; table 1). Consistent with OPUS shared solution requirements (NOAA, 2022), DGGS considers high-quality GNSS solutions to have vertical errors less than or equal to 0.08 m. We quantified the vertical accuracy of the DSM using the same 12 check points used to quantify the horizontal accuracy. The RMS error of Z offsets is 0.025 m. The total RMS error of the DSM (X, Y, and Z) is 0.053 m.Ground survey - On July 8, 2022, DGGS set up a Global Navigation Satellite System (GNSS) base station using a Trimble R10 receiver sampling at 5 Hz over a temporary benchmark. This provided real-time kinematic (RTK) corrections to the ground rover, a Trimble R8s GNSS receiver. DGGS measured the location of 25 photo-identifiable ground control points (GCPs) with the ground rover.20220708Aerial survey - DGGS conducted flights on July 8, 2022, from approximately 2:30 PM to 7:15 PM AKDT. DGGS used a DJI Phantom 4 RTK UAV with a FC6310R camera model (8.8 mm lens) to collect 1,935 20-megapixel JPEG photographs (5,472 x 3,648 pixels per image). The operator returned the UAV 10 times to change batteries. DGGS flew the aerial survey with 70 percent sidelap and 70 percent frontlap, 112 m above ground-level at 9.0 m/s, with nadir orientation stabilized using a three-axis gimbal. This resulted in images covering 3.675 km2 with a ground sampling distance (GSD) of 0.024 m. The weather throughout the survey was clear with light wind. No abnormalities were observed during the flights.20220708Dataset processing - Base positions were corrected using Online Positioning User Service (OPUS) solutions, which were used to update the UAV and ground rover positions with post-processed kinematic (PPK) adjustments. UAV positions were updated in RTKLIB (Version 2.4.3) software with the following settings applied: L1+L2 frequencies forward and backward filtered; a 10 degree elevation mask; receiver dynamics disabled; broadcast ionosphere and Saastamoinen troposphere corrections; a minimum fixed-ambiguity ratio of three; and L1/L2 code/carrier-phase error ratios of 100/100. During post-processing, DGGS applied International GNSS Service (IGS) precise orbits and final clock solutions retrieved from the Crustal Dynamics Data Information System (CDDIS) found at urs.earthdata.nasa.gov. Final corrected data were exported as time-stamped position files in WGS84 horizontal coordinate system with ellipsoidal heights and paired to corresponding photographs using an Aerotas P4RTK PPK Adjustments (Version 1) macro-enabled Microsoft Excel file. Ground rover positions were updated using PPK corrections in Trimble Business Center (Version 5.51) software using default settings. Final corrected data were exported as comma-delimited text files in WGS84 horizontal coordinate system with ellipsoidal heights. DGGS used Agisoft Metashape Professional (Version 1.8.3 build 14331) software for photogrammetric processing following the steps and settings outlined in Over and others (2021). During processing, DGGS used 13 GCPs for photograph alignment and lens distortion parameter optimization, leaving 12 GCPs as horizontal and vertical check points. A confidence filter was applied to the resulting dense point cloud, eliminating all points derived from fewer than three discrete camera positions. Additional noise was removed from the dense point cloud through visual inspection.2023rasterUniversal Transverse Mercator30.999600-1650500000.0000000coordinate pair.00000001.00000001MetersNAD83 (2011)GRS 806378137298.257222101NAVD88, GEOID12B0.001metersExplicit elevation coordinate included with horizontal coordinatesboundariesA boundary, also known as an Area of Interest (AOI) or border, that defines the area covered by the data. Also includes footprints for tiled data.DGGSboundariesdsmThe DSM represents surface elevations including the height of vegetation, buildings, and other man-made features derived from the dense point cloud. The DSM is a single-band, 32-bit floating point GeoTIFF file with a GSD of 0.071 m; the No Data value is set to -3.4028235e+38.DGGSdsmortho_rgbThe orthoimage is a three-band (red, green, blue), eight-bit unsigned GeoTIFF file derived from a color-adjusted mosaic of 1,864 aerial photographs with a GSD of 0.024 m per pixel; the No Data value is set to 0.DGGSortho_rgbAlaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical

3354 College Road

FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysFGDC Content Standard for Digital Geospatial MetadataFGDC-STD-001-1998If 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.extdggs metadata extensions