Identification_Information: Citation: Citation_Information: Originator: Buzard, R.M. Originator: Christian, J.E. Originator: Overbeck, J.R. Publication_Date: 2022 Title: Photogrammetry-derived orthoimagery and elevation for Saint Paul, Alaska, collected July 22-25, 2021 Geospatial_Data_Presentation_Form: orthoimage Series_Information: Series_Name: Raw Data File Issue_Identification: RDF 2022-1 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 7 p. Online_Linkage: https://doi.org/10.14509/30836 Description: Abstract: The State of Alaska Division of Geological & Geophysical Surveys (DGGS) collected low-altitude aerial images from an unmanned aerial vehicle (UAV) from July 22 to 25, 2021 and used Structure-from-Motion (SfM) photogrammetry to produce digital surface models (DSMs) and orthoimagery of North Beach, Polovina Beach, and the City of Saint Paul, Alaska. The orthoimagery 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. We used Agisoft Metashape Professional to process the 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/10.14509/30836). Purpose: The orthoimagery and elevation data are for assessing coastal hazards and changes on Saint Paul Island. Supplemental_Information: >digital surface model: The DSM represents surface elevations such as the height of vegetation and buildings. Water bodies can introduce noise. For North, Benson, and Polovina beaches, we manually delineated the ocean boundary to restrict the DSM to the land. For the city DSM, we did not remove water areas because the model includes rocky islets and shallow underwater features of interest (most notably the submerged groins at the northwest breakwater). We filtered the dense cloud to remove low confidence points (most often water surfaces) and prioritize seafloor elevation. However, we do not expect absolute seafloor elevation to be as accurate as above-water features. The DSM is a single-band, 32-bit floating point GeoTIFF file with the "No Data" value set to -3.4028231 x 10^38. >orthoimagery: The orthoimagery is a three-band (red, green, blue) 8-bit unsigned GeoTIFF file with the "No Data" value set to 0. GSD varies by location, cee the accompanying report for details. Time_Period_of_Content: Time_Period_Information: Range_of_Dates/Times: Beginning_Date: 20210622 Ending_Date: 20210625 Currentness_Reference: ground condition Status: Progress: complete Maintenance_and_Update_Frequency: None planned Spatial_Domain: Bounding_Coordinates: West_Bounding_Coordinate: -170.215434 East_Bounding_Coordinate: -170.210455 North_Bounding_Coordinate: 57.152016 South_Bounding_Coordinate: 57.148986 Keywords: Theme: Theme_Keyword_Thesaurus: ISO 19115 Topic Category Theme_Keyword: geoscientificInformation Theme: Theme_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Theme_Keyword: Aerial Theme_Keyword: Aerial Geology Theme_Keyword: Aerial Photography Theme_Keyword: Coastal Theme_Keyword: Coastal Erosion Theme_Keyword: Coastal and River Theme_Keyword: DGGS Theme_Keyword: Digital Surface Model (DSM) Theme_Keyword: Elevation Theme_Keyword: Emergency Preparedness Theme_Keyword: Engineering Theme_Keyword: Engineering Geology Theme_Keyword: Environmental Theme_Keyword: Erosion Theme_Keyword: Flood Theme_Keyword: Geologic Theme_Keyword: Geologic Hazards Theme_Keyword: Geological Process Theme_Keyword: Geology Theme_Keyword: Geomorphology Theme_Keyword: Geotechnical Theme_Keyword: Hazards Theme_Keyword: Orthoimagery Theme_Keyword: Photogrammetry Theme_Keyword: Raster Image Theme_Keyword: Remote Sensing Theme_Keyword: Sea Level Changes Theme_Keyword: Shaded Relief Theme_Keyword: Structure From Motion Theme_Keyword: Surface Theme_Keyword: Surficial Theme_Keyword: Surficial Geology Theme_Keyword: Topography Theme_Keyword: Water Theme_Keyword: Web Service Place: Place_Keyword_Thesaurus: Alaska Division of Geological & Geophysical Surveys Place_Keyword: Bering Sea Place_Keyword: Pribilof Islands Quadrangle Place_Keyword: Saint Paul Place_Keyword: Saint Paul Island 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. Point_of_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Position: Metadata Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907)451-5020 Contact_Facsimile_Telephone: (907)451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Contact_Instructions: 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. Data_Set_Credit: We thank the Aleut Community of Saint Paul Island for funding and supporting the creation of these data products. Cross_Reference: Citation_Information: Originator: Suleimani, E.N. Originator: Nicolsky, D.J. Originator: Salisbury, J.B. Publication_Date: 2020 Title: Regional tsunami hazard assessment for communities of Bristol Bay and the Pribilof Islands, Alaska Series_Information: Series_Name: Report of Investigation Issue_Identification: RI 2020-1 Publication_Information: Publication_Place: Fairbanks, Alaska, United States Publisher: Alaska Division of Geological & Geophysical Surveys Other_Citation_Details: 32 p., 6 sheets Online_Linkage: https://doi.org/10.14509/30422 Data_Quality_Information: Attribute_Accuracy: Attribute_Accuracy_Report: Not applicable Logical_Consistency_Report: 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. Completeness_Report: This data release is complete. Positional_Accuracy: Horizontal_Positional_Accuracy: Horizontal_Positional_Accuracy_Report: We quantify the horizontal accuracy of the DSMs and orthoimagery by comparing the known locations of photo-identifiable check points measured with GNSS against their modeled locations in the photogrammetric products. 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. Horizontal accuracy of the Polovina Beach DSM and orthoimage is not assessed. See the accompanying report for tables of checkpoint comparisons. Vertical_Positional_Accuracy: Vertical_Positional_Accuracy_Report: We assess vertical accuracy of the City and North and Benson beaches DSM products using the same check points that are used for horizontal accuracy. For North and Benson beaches, the RMS error of Z offsets is 0.020 m, and the total error of the DSM (X, Y, and Z) is 0.036 m. For the city survey, the RMS error of Z offsets is 0.028 m, and the total error of the DSM is 0.050 m (table 3). Vertical accuracy is not evaluated for offshore and underwater features. We assess vertical accuracy of the Polovina Beach DSM using the RMS error of the fit to eleven GCPs at bare-earth locations. The vertical RMS error of the GCPs is 0.017 m. The RMS error of the vertical correction is 0.054 m (n = 11). The total error is 0.056 m (root-sum-square error of the control and fit RMS errors. See the accompanying report for tables of checkpoint comparisons.). Lineage: Process_Step: Process_Description: 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 surveys with 70 percent sidelap, 80 percent frontlap, and nadir camera orientation stabilized by a 3-axis gimbal. The survey was flown between 100 and 120 m above the ground at 5.5 to 7.9 m/s, respectively. The resulting images cover 1.21 km2 with ground sampling distance (GSD) of approximately 0.03 m. DGGS surveyed North and Benson beaches on July 22, 2021, from 4:00 PM to 4:30 PM AKDT. The operator returned the UAV once to change batteries. We flew the Black Bluffs in the east area of the City of Saint Paul on July 23, 2021, from 12:55 PM to 1:05 PM, with the camera oriented 10 degrees off-nadir towards the bluff face. This orientation improved mapping of the vertical bluff face. We flew Polovina Beach on July 23, 2021, from 1:50 PM to 2:00 PM AKDT using one battery. We flew the City of St. Paul on July 25, 2021, from 6:40 PM to 7:40 PM AKDT. The operator returned the UAV twice to change batteries. This survey overlapped with the Black Bluffs survey so we combined the final products. The weather throughout all surveys was overcast with no rain and light to moderate wind. No abnormalities were observed during the flights. Process_Date: 20210625 Process_Step: Process_Description: Ground survey - DGGS set up a GNSS base station using a Trimble R10 receiver sampling at 5 Hz. The base was installed over a benchmark with a published solution (found at www.ngs.noaa.gov/OPUS/get Datasheet.jsp?PID=BBCN02). This provided real-time kinematic (RTK) corrections to the Trimble R8s GNSS receiver. DGGS measured 22 photo-identifiable points with the R8s. DGGS installed temporary benchmarks using the R8s and subsequently occupied these benchmarks with the base station. We derived the corrected base positions using the Online Positioning User Service (found at www.ngs.noaa.gov/OPUS/) and post-processed the R8s positions in Trimble Business Center. Process_Date: 20210625 Process_Step: Process_Description: Photogrammetric dataset processing - For the surveys at North Beach, Polovina Beach, and the community of Saint Paul the UAV did not maintain RTK connection with the Trimble R10 base station. We apply a post-processing kinematic correction using RTKLIB (an open-source GNSS processing software found at www.rtklib.com). The UAV GNSS receiver samples at 5 Hz, rather than at image acquisition times. We interpolate the corrected positions at image timestamps to derive coordinates. The image timestamp metadata also contains orientation to support the lever arm correction that adjusts coordinates from the GNSS receiver to the camera. We compute the interpolation and lever arm correction using the worksheet found at www.aerotas.com/phantom-4-rtk-ppk-processing-workflow. For the city survey, the UAV maintained RTK connection. 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. The UAV positions are updated using a X, Y, and Z shift from the initial to the corrected base position. DGGS processed images in 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 ground control points (GCPs), manually cleaning the sparse point cloud, optimizing the bundle block adjustment (refining camera positions and lens distortion parameters), constructing the dense point cloud, building the DSM, and creating the orthomosaic image. For the city, we used eight GCPs to create the model, leaving four survey check points. For North and Benson beaches, six GCPs and four check points. For Polovina beach, we could only collect elevation points that were not photo-identifiable. We vertically adjust the elevation model using the average offset of eleven vertical points. Process_Date: 2021 Spatial_Data_Organization_Information: Direct_Spatial_Reference_Method: raster Spatial_Reference_Information: Horizontal_Coordinate_System_Definition: Planar: Grid_Coordinate_System: Grid_Coordinate_System_Name: Universal Transverse Mercator Universal_Transverse_Mercator: UTM_Zone_Number: 2 Transverse_Mercator: Scale_Factor_at_Central_Meridian: 0.999600 Longitude_of_Central_Meridian: -171 Latitude_of_Projection_Origin: 0 False_Easting: 500000.000000 False_Northing: 0 Planar_Coordinate_Information: Planar_Coordinate_Encoding_Method: coordinate pair Coordinate_Representation: Abscissa_Resolution: .00000001 Ordinate_Resolution: .00000001 Planar_Distance_Units: Meters Geodetic_Model: Horizontal_Datum_Name: NAD83 (2011) Ellipsoid_Name: GRS 80 Semi-major_Axis: 6378137 Denominator_of_Flattening_Ratio: 298.257222101000025 Entity_and_Attribute_Information: Detailed_Description: Entity_Type: Entity_Type_Label: digital surface model Entity_Type_Definition: The DSM represents surface elevations such as the height of vegetation and buildings. Water bodies can introduce noise. For North, Benson, and Polovina beaches, we manually delineated the ocean boundary to restrict the DSM to the land. For the city DSM, we did not remove water areas because the model includes rocky islets and shallow underwater features of interest (most notably the submerged groins at the northwest breakwater). We filtered the dense cloud to remove low confidence points (most often water surfaces) and prioritize seafloor elevation. However, we do not expect absolute seafloor elevation to be as accurate as above-water features. The DSM is a single-band, 32-bit floating point GeoTIFF file with the "No Data" value set to -3.4028231 x 10^38. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: digital surface model Detailed_Description: Entity_Type: Entity_Type_Label: orthoimagery Entity_Type_Definition: The orthoimagery is a three-band (red, green, blue) 8-bit unsigned GeoTIFF file with the "No Data" value set to 0. GSD varies by location, cee the accompanying report for details. Entity_Type_Definition_Source: DGGS Entity_Attribute_Layer_Name: orthoimagery Distribution_Information: Distributor: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Position: Metadata Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907)451-5020 Contact_Facsimile_Telephone: (907)451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Contact_Instructions: 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. Resource_Description: RDF 2022-1 Distribution_Liability: 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. Standard_Order_Process: Non-digital_Form: DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount. Fees: Contact DGGS for current pricing Standard_Order_Process: Digital_Form: Digital_Transfer_Information: Format_Name: orthoimage Format_Version_Date: 20220209 Format_Information_Content: digital surface model and orthoimagery Digital_Transfer_Option: Online_Option: Computer_Contact_Information: Network_Address: Network_Resource_Name: https://doi.org/10.14509/30836 Fees: Free download Metadata_Reference_Information: Metadata_Date: 20220211 Metadata_Contact: Contact_Information: Contact_Organization_Primary: Contact_Organization: Alaska Division of Geological & Geophysical Surveys Contact_Person: Simone Montayne Contact_Position: Metadata Manager Contact_Address: Address_Type: mailing and physical Address: 3354 College Road City: Fairbanks State_or_Province: AK Postal_Code: 99709-3707 Country: USA Contact_Voice_Telephone: (907)451-5020 Contact_Facsimile_Telephone: (907)451-5050 Contact_Electronic_Mail_Address: dggspubs@alaska.gov Hours_of_Service: 8 am to 4:30 pm, Monday through Friday, except State holidays Metadata_Standard_Name: FGDC Content Standard for Digital Geospatial Metadata Metadata_Standard_Version: FGDC-STD-001-1998 Metadata_Use_Constraints: 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. Metadata_Extensions: Online_Linkage: https://dggs.alaska.gov/metadata/dggs.ext Profile_Name: dggs metadata extensions