Maxwel F. Schwid Mackenzie K. Keith Brandon T. Overstreet 20250826 raster digital data https://doi.org/10.5066/P135FWPP In cooperation with the U.S. Army Corps of Engineers (USACE), the U.S. Geological Survey (USGS) surveyed ground control points and coordinated aerial photograph acquisition of Hills Creek Lake, a multi-purpose reservoir in western Oregon impounded by the 92-meter ([m]; 302-foot [ft]) tall Hills Creek Dam. Aerial photographs were acquired by the Civil Air Patrol (CAP) on December 20, 2023 and December 28, 2023 when water levels were at 443 and 441 m (1453 ft and 1448 ft; National Geodetic Vertical Datum of 1929 [NGVD 29]) elevation, respectively, about 10 m above typical annual “low pool” or minimum pool for flood risk management operations. Photographs were acquired at about the same altitude with a WaldoAir XCAM Ultra 50 camera mounted on a Cessna aircraft and captured the entire reservoir area as defined by full pool (or maximum conservation pool elevation), including major tributaries entering the reservoir such as the Middle Fork Willamette River and Hills Creek, upstream of Hills Creek Dam. Dam operations at the 1,107-hectare (2735-acre) Hills Creek Lake, located about 19 kilometers upstream of the confluence of the Middle Fork Willamette River and the head of Lookout Point Lake, along with other hydrogeomorphic conditions, result in a diverse array of geomorphic processes and landforms within the reservoir. To document reservoir floor geomorphology, the USGS applied structure-from-motion (SfM) techniques to these aerial photographs, following the workflow outlined in Over and others (2021), and generated three-dimensional xyz point clouds, digital surface models (DSMs), and orthomosaics of Hills Creek Lake. This data release includes ground control points, dataset footprints, original aerial photographs, point clouds, DSMs, and orthomosaics of Hills Creek Lake with varying aerial extents and resolutions that were developed from imagery acquired December of 2023: (1) the December 20 model (HillsCreekLake_20231220) covered the entire reservoir area with an average point density of 27.6 points per square meter, DSM resolution of 19 centimeters per pixel, and orthomosaic ground resolution of 9.52 centimeters per pixel; (2) the December 28 model (HillsCreekLake_20231228) covered the entire reservoir area, excluding a portion of the Larison Creek arm, with an average point density of 29.8 points per square meter, DSM resolution of 18.3 centimeters per pixel, and orthomosaic ground resolution of 9.15 centimeters per pixel. All DSMs and orthomosaics are formatted as Cloud Optimized GeoTIFFs (COGs) for enhanced web visualization (GDAL, 2024). This documentation describes a DSM of Hills Creek Lake, Oregon, generated from SfM techniques using aerial photographs acquired on December 28, 2023. References: Agisoft, 2025, Agisoft Metashape User Manual - Professional Edition Version 2.2: Agisoft LLC, 115 p., accessed August 11, 2025, at https://www.agisoft.com/pdf/metashape_2_2_en.pdf. American Society for Photogrammetry and Remote Sensing [ASPRS], 2008, LAS Specification Version 1.2: ASPRS, approved September 2, 2008, 13 p., accessed August 11, 2025, at https://www.asprs.org/wp-content/uploads/2010/12/asprs_las_format_v12.pdf. Geospatial Data Abstraction Library [GDAL], 2024, COG -- Cloud Optimized GeoTIFF generator: GDAL, webpage, accessed August 11, 2025, at https://gdal.org/drivers/raster/cog.html#raster-cog. Over, J.R., Ritchie, A.C., Kranenburg, C.J., Brown, J.A., Buscombe, D., Noble, T., Sherwood, C.R., Warrick, J.A., and Wernette, P.A., 2021, Processing coastal imagery with Agisoft Metashape Professional Edition, version 1.6—Structure from motion workflow documentation: U.S. Geological Survey Open-File Report 2021–1039, 46 p., https://doi.org/10.3133/ofr20211039. Schwid, M.F., Keith, M.K., and Overstreet, B.T., 2025, High-resolution orthoimagery and digital surface models of Fern Ridge Lake, Oregon, during annual low pool, January and February, 2023: U.S. Geological Survey data release, https://doi.org/10.5066/P1Q5K657. The original aerial photographs acquired by CAP, along with the point clouds, DSMs, and orthomosaics covering Hills Creek Lake were created to provide high-resolution datasets depicting the reservoir floor that are exposed during low pool (443 and 441 m/1453 ft and 1448 ft NGVD 29) conditions. These datasets are useful for evaluating geomorphic characteristics of the reservoir floor and assessing other landscape conditions; when compared with future datasets, these datasets will also be useful for tracking changes in reservoir floor conditions. 20231228 ground condition Complete None planned -122.45592 -122.37065 43.72249 43.59760 ISO 19115 Topic Categories biota elevation environment inlandWaters geoscientificInformation imageryBaseMapsEarthCover USGS Thesaurus structure from motion geospatial analysis aerial photography remote sensing geomorphology geospatial datasets digital elevation models image collections GPS measurement None fluvial geomorphology SfM photogrammetry orthoimagery orthophotograph orthomosaic GeoTIFF Cloud Optimized GeoTIFF dam reservoir drawdown river processes Civil Air Patrol Cessna Waldo USGS Metadata Identifier USGS:68193abed4be0208bc3e047c Geographic Names Information System (GNIS) Hills Creek Hills Creek Lake Lane County Larison Cove Larison Creek Middle Fork Willamette River Packard Creek State of Oregon None Willamette Valley none These data are in the public domain in accordance with Creative Commons Zero v1.0 Universal Public Domain Dedication (CC0-1.0) and have no use constraints. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. The U.S. Geological Survey shall not be held liable for improper or incorrect use of the data retrieved from the system. Public domain data from the U.S. Government are freely redistributable with proper metadata and source attribution. The U.S. Geological Survey should be acknowledged as the data source in products derived from these data. Schwid, Maxwel F. U.S. Geological Survey Hydrologist Mailing and Physical

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Portland OR 97204 United States 503-758-5589 gs-w-or_sciencebase@usgs.gov Funding for this study was provided by the U.S. Army Corps of Engineers. None Unclassified None Agisoft Metashape Professional Version 2.2.0; Esri ArcGIS Pro Version 3.2.49743; GDAL Version 3.6.2. An R12i Trimble global navigation satellite system (GNSS) receiver with Trimble’s real-time precise point positioning technology, Real Time eXtended (RTX), was used to collect the ground control points. All data were acquired and handled in a consistent manner. Two crewed flights were contracted through the USACE to the Civil Air Patrol, Eugene, Oregon on December 20 and December 28, 2023. A total of 1,427 aerial photographs were captured at an average flight altitude about 1,700 meters above ground level, collectively covering about 43 square kilometers. Photographs were acquired as three-band (RGB) images in JPEG format using a WaldoAir XCAM Ultra 50 camera, consisting of two oblique-mounted Canon EOS 5DS R cameras that were triggered simultaneously, mounted to a Cessna 182 aircraft. A NovAtel OEMStar GPS recorded camera positions in the image file EXIF data in UTC time zone. All aerial photographs were contemporaneously aligned in Agisoft Metashape software. Agisoft software determined which aerial photographs were used in SfM product (point clouds, DSMs, and orthomosaics) generation based on photograph alignment and the validity of identified tie points, which represent common pixels in photographs as determined by the software. To provide check points for model accuracies, a portion of the ground control points were excluded from SfM product generation and used for model validation. Specifically, 15 checkpoints out of the 56 survey points were excluded for the December 20, 2023, datasets and 12 out of 57 were excluded for the December 28, 2023, datasets. The tie points were visually inspected and filtered to exclude obvious anomalous points from the derivative products (dense point clouds, DSMs, and orthomosaics). Aligned, referenced aerial photographs and their corresponding filtered tie points were separated into the two domains (20231220 and 20231228) for dense point cloud and derivative product generation. The orthomosaics contain compression-derived artifacts occurring as erroneous pixel values that border the outer extent of each rasters’ multiple overviews; these artifacts do not occur in, nor affect the underlying full-resolution images. Photographs from the two flights were processed separately after alignment due to differences in ground conditions during collection, including reservoir pool elevations and sun angle/shadowing. The dataset is considered complete and consists of ground control points, coverage footprints, raw aerial photographs, dense point clouds, DSMs, and orthomosaics for the two separate acquisition efforts. All 64 surveyed ground control points are listed in the CSV text file and all 1,427 aerial photographs are included in each associated zipped flight file. All aerial photographs were used to create SfM products (point clouds, DSMs and orthomosaics). Dense point clouds were generated for each domain from tie points identified in the Agisoft Metashape software after a standardized filtering process that excludes low-certainty or anomalous points. Filtered dense point clouds were used to create DSMs and orthomosaics. The dense point clouds and DSMs generated may contain false topography and high error propagated from the software’s identification of false tie points below the translucent, shallow water surface of the pool or in areas influenced by lake waves (Over and others, 2021). The DSMs and orthomosaics were clipped during export from Agisoft software to exclude areas of high uncertainty or distortion, particularly in densely vegetated or forested areas or near edges where minimal photograph overlap inhibited photogrammetric processing. Differences in spatial extent of the datasets resulted from variations in photograph coverage between the two flights. No formal horizontal accuracy tests were performed. Sources of potential error that affect the horizontal accuracy include ground control point accuracy and error incurred during alignment, optimization, and ground control processing procedures within the Agisoft Metashape software. Although the aerial photograph locations (recorded by a NovAtel OEMStar GPS located on the aircraft) are used by the photogrammetric software during initial alignment, these location data are not included in the generation of any derivative products and therefore the positional accuracy and potential errors do not contribute to the overall horizontal accuracy of the products (point clouds, DSMs, and orthomosaics). Horizontal accuracy likely decreases with distance from ground control. Ground control points surveyed with an RTX-enabled GNSS receiver had a reported horizontal precision ranging from 0.01 to 0.30 meters. Though not an assessment of horizontal or vertical accuracy, horizontal positions of ground control points were used to calculate a root mean square (RMS) estimate of positional error at discrete locations by the photogrammetric software and are described here. Additionally, residuals between withheld ground control points (check points) and the model can serve as an indication of accuracy. Ground control and check point error is reported by the software with precision that is higher than provided by model inputs (RTX-GNSS precision) and thus has been rounded. For the December 20 model, 41 ground control points were used to construct SfM datasets, and the model had a horizontal error of 21 centimeters, vertical error of 10 centimeters, and overall error of 24 centimeters. The 15 ground control points withheld as check points were compared to the model and had a horizontal error of 44 centimeters, vertical error of 23 centimeters, and overall error of 49 centimeters. For the December 28 model, 45 ground control points were used to construct SfM datasets, and the model had a horizontal error of 14 centimeters, vertical error of 5 centimeters, and total error of 15 centimeters. The 12 ground control points withheld as check points were compared to the model and had a horizontal error of 30 centimeters, vertical error of 32 centimeters, and overall error of 44 centimeters. Visual comparison of generated orthomosaics to publicly available aerial imagery indicated horizontal displacement was minimal for all datasets, although some obvious distortion (for example, holes, blurry areas, and discontinuity or irregularity of linear features) is noticeable where vegetation is present or there was very little photograph overlap. Increasing noise at surface water locations occurs within each model; these areas were not edited. No formal vertical accuracy tests were performed. However, vertical accuracy likely decreases with distance from ground control. Ground control points surveyed with an RTX-enabled GNSS receiver had a reported vertical precision ranging from 0.03 to 0.93 meters. Though not an assessment of horizontal or vertical accuracy, horizontal positions of ground control points were used to calculate an RMS estimate of positional error at discrete locations by the photogrammetric software and are described here. Additionally, residuals between withheld ground control points and the model can serve as an indication of accuracy. Ground control and check point error is reported by the software with precision that is higher than provided by model inputs (RTX-GNSS precision) and thus has been rounded. For the December 20 model, 41 ground control points were used to construct SfM datasets, and the model had a horizontal error of 21 centimeters, vertical error of 10 centimeters, and overall error of 24 centimeters. The 15 ground control points withheld as check points were compared to the model and had a horizontal error of 44 centimeters, vertical error of 23 centimeters, and overall error of 49 centimeters. For the December 28 model, 45 ground control points were used to construct SfM datasets, and the model had a horizontal error of 14 centimeters, vertical error of 5 centimeters, and total error of 15 centimeters. The 12 ground control points withheld as check points were compared to the model and had a horizontal error of 30 centimeters, vertical error of 32 centimeters, and overall error of 44 centimeters. Digital surface models, particularly in edge areas where photograph overlap was limited, may contain false topography as a result of the photogrammetric reconstruction process and/or model interpolation within sparse dense point cloud areas. American Society for Photogrammetry and Remote Sensing 20080902 publication online American Society for Photogrammetry and Remote Sensing https://www.asprs.org/wp-content/uploads/2010/12/asprs_las_format_v12.pdf Digital and/or Hardcopy 20080902 publication date ASPRS (2008) Laser file format specifications for point clouds. Jin-Si R. Over Andrew C. Ritchie Christine J. Kranenburg Jenna A. Brown Daniel D. Buscombe Tom Noble Christopher R. Sherwood Jonathan A. Warrick Phillipe A. Wernette 2021 publication online U.S. Geological Survey https://doi.org/10.3133/ofr20211039 Digital and/or Hardcopy 20210614 publication date Over and others (2021) Software settings and processing procedures. Maxwel F. Schwid Mackenzie Keith Brandon T. Overstreet 2025 dataset https://www.sciencebase.gov U.S. Geological Survey https://doi.org/10.5066/p1q5k657 Digital and/or Hardcopy 20250311 publication date Schwid and others (2025) Software settings and processing procedures. Agisoft 2025 publication online Agisoft https://www.agisoft.com/pdf/metashape_2_2_en.pdf Digital and/or Hardcopy 20250211 publication date Agisoft (2025) Software settings and processing procedures. Geospatial Data Abstraction Library (GDAL) 2024 3.6.2 application/service online Geospatial Data Abstraction Library (GDAL) https://gdal.org/drivers/raster/cog.html#raster-cog https://gdal.org/api/python_bindings.html Digital and/or Hardcopy 20240218 publication date GDAL (2024) Raster conversion program for Cloud Optimized GeoTIFF creation. Aerial photographs were acquired by the Civil Air Patrol on December 20, 2023, between 14:04 to 14:47 Pacific Standard Time (PST) covering approximately 43 square kilometers of the reservoir area. Photographs were acquired as high-resolution JPG images using a WaldoAir XCAM Ultra 50 camera, consisting of two oblique-mounted Canon EOS 5DS R cameras that are triggered simultaneously, mounted to a Cessna 182 aircraft. A NovAtel OEMStar GPS recorded camera positions in the image file EXIF data in UTC time zone. The pilot flew in longitudinal passes at about 1,700 meters above ground level over Hills Creek Lake. A total of 918 photos were taken from takeoff to landing of flight. 20231220 Aerial photographs were acquired by the Civil Air Patrol on December 28, 2023, between 13:49 to 14:12 Pacific Standard Time (PST) covering approximately 40 square kilometers of the reservoir area. Photographs were acquired as high-resolution JPG images using a WaldoAir XCAM Ultra 50 camera, consisting of two oblique-mounted Canon EOS 5DS R cameras that are triggered simultaneously, mounted to a Cessna 182 aircraft. A NovAtel OEMStar GPS recorded camera positions in the image file EXIF data in UTC time zone. The pilot flew in longitudinal passes at about 1,700 meters above ground level over Hills Creek Lake. A total of 509 photos were taken from takeoff to landing of flight. 20231228 The USGS surveyed 64 control point features throughout Hills Creek Lake on December 17, 2024, using an RTX-enabled GNSS receiver. The control points consisted of static infrastructure features (for example, parking lot pavement arrows, retaining-wall corners, stumps) that were visible in the photographs. 20241217 All 1,427 photographs from the December 20 and December 28 flights were added to Agisoft Metashape software (v. 2.2.0) for alignment to identify tie points (common pixels the software identifies between photos). All subsequent steps conducted in Agisoft Metashape software follow the workflow outlined in Over and others (2021). Camera groups were created based on the two oblique cameras, but all photos remained in a single chunk. The coordinate system of the aerial photographs was converted from WGS84 (EPSG:4326) to NAD83(2011) UTM Zone 10 North (EPSG:6339) for the horizontal datum and projection and NAVD88 meters, GEOID 18 (EPSG:5703) for the vertical datum. The following reference settings were updated: measurement camera accuracy of 150 meters and marker accuracy of 0.1 meters; image coordinates marker accuracy of 1 pixel and tie point accuracy of 1 pixel 2025 All aerial photographs were aligned together with an accuracy setting of "High", the generic preselection box checked, the reference preselection box checked and set to "Source," key point limit set to 60,000, and tie point limit set to 0 (meaning no tie point limit). The "Exclude stationary tie points," "Guided image matching," and "Adaptive camera model fitting" boxes were all left unchecked. 2025 The camera calibration model was optimized with the following coefficients: f, cx, cy, k1, k2, k3, p1, p2, and where f is focal length; cx and cy are the optimal point; k is radial distortion; and p translational distortion. 2025 Aligned aerial photographs and their tie points were separated into two chunks by selecting the associated aerial photographs and separating them into individual chunks. 2025 A ground control point file (CSV) containing XYZ coordinates (NAD83(2011) UTM Zone 10 North (EPSG:6339) and NAVD88 meters, GEOID 18 (EPSG:5703)) was imported to both chunks. The Agisoft software identified photos that contained each marker. Photographs were filtered by each marker and were inspected for marker placement relative to the ground control point visible in each photo. Markers were either left in their position and verified, moved to the correct position and verified, or removed. An even spatial distribution of ground control points were converted to check points in each chunk for use in later model accuracy assessment (see CSV). Camera GPS locations were excluded from further processing by unchecking (not disabling) all cameras in the reference-camera pane. 2025 The camera calibration models for each chunk were optimized with the following coefficients: f, cx, cy, k1, k2, k3, p1, p2, where f is focal length; cx and cy are the optimal point; k is radial distortion; and p translational distortion. 2025 The sparse clouds of photogrammetric tie points generated during alignment for each chunk (3.4 million for December 20; 1.8 million for December 28) were gradually filtered based on several criteria of model fit to identify and remove points with high reprojection error, with camera calibration model optimization in between each filtering step. First, the point clouds were visually inspected for anomalous points which were selected then deleted. Second, points with a “Reconstruction uncertainty” greater than 12.3 for December 20 and 12.6 for December 28 were selected then deleted; this removed approximately 2.6 million and 1.4 million points, respectively, that were generated due to poor camera geometries. The camera calibration models were then optimized with the following coefficients: f, cx, cy, k1, k2, k3, p1, p2. Third, points with a “Projection accuracy” greater than 4.1 for December 20 and 5.0 for December 28 were selected then deleted; this removed approximately 0.7 million and 0.3 million points, respectively, that were generated due to pixel matching errors derived from variations in image scaling. The camera calibration models were then optimized with the following coefficients: f, cx, cy, k1, k2, k3, p1, p2. Last, points with a “Reprojection error” greater than 0.3 for both models were iteratively selected and deleted, without exceeding 10% of all points with each selection; this removed approximately 0.01 million points for the December 20 model and 0.01 million points for the December 28 model that were incorrectly reprojected after alignment. The camera calibration models were then optimized with the following coefficients: f, cx, cy, k1, k2, k3, k4, p1, p2, b1, b2, with “Fit additional corrections” checked. The final unweighted RMS reprojection error for the tie point clouds was 0.35 pixels for the December 20 model and 0.47 pixels for the December 28 model. 2025 Dense point clouds were built for each of the two chunks using the high quality setting and mild depth filtering. Any anomalous or “floating” points were visually inspected and deleted. 2025 DSMs were built for each of the two chunks using the dense point clouds and interpolation enabled. Color for each chunk was homogenized using the "Calibrate Colors" with the "Calibrate white balance" option checked. 2025 Orthomosaics were built for each of the two chunks using the Mosaic blending mode, digital elevation model (DEM) surface, hole filling enabled, and default pixel size. 2025 All SfM products were exported using their default resolutions. Dense point clouds and DSMs were exported for each of the two chunks using the default settings. Orthomosaics were exported without compression and saved as BigTIFF files. DSMs and orthomosaics were clipped using imported polygons to remove distorted areas or areas with missing raster values. 2025 DSMs and orthomosaics for the two chunks were converted from standard GeoTIFFs to Cloud Optimized GeoTIFFs (COGs) using the Python binding of the Geospatial Data Abstraction Library’s (GDAL) COG raster driver (GDAL, 2024). Standard raster driver settings were maintained except for the following: DSMs were created using LZW (lossless) compression, floating point predictor, bilinear overview resampling, and BigTIFF set to “IF_SAFER;” orthomosaics were created using JPEG compression (default quality of 75), bilinear resampling, and BigTIFF set to “IF_SAFER.” This JPEG compression may alter pixel values from the original values output by the Agisoft software. Orthomosaics contain compression-derived artifacts occurring as erroneous pixel values that border the outer extent of each rasters’ multiple overviews; these artifacts do not occur in, nor affect the underlying full resolution images. 2025 Raster Pixel 75540 37039 1 Universal Transverse Mercator 10 0.9996 -123.0 0.0 500000.0 0.0 row and column 0.18299499999999894 0.18299500000000302 meters NAD83_National_Spatial_Reference_System_2011 GRS 1980 6378137.0 298.257222101 North American Vertical Datum of 1988 0.001 meters Explicit elevation coordinate included with horizontal coordinates HillsCreekLake_20231228_dsm.tif Elevation raster Other Value Elevation Agisoft Metashape 0 NoData Producer defined 371.225 881.146 Meters U.S. Geological Survey - ScienceBase Mailing and Physical

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Although these data have been used by the U.S. Geological Survey, U.S. Department of the Interior, no warranty expressed or implied is made by the U.S. Geological Survey as to the accuracy of the data. The act of distribution shall not constitute any such warranty, and no responsibility is assumed by the U.S. Geological Survey in the use of these data, software, or related materials. The use of firm, trade, or brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey. The names mentioned in this document may be trademarks or registered trademarks of their respective trademark owners. GeoTIFF GDAL 3.6.2 32-bit TIFF 32-bit floating point Cloud Optimized GeoTIFF with LZW compression and FGDC CSDGM metadata LZW compression. 3620 https://doi.org/10.5066/P135FWPP https://prod-is-usgs-sb-prod-publish.s3.amazonaws.com/68193abed4be0208bc3e047c/HillsCreekLake_20231228_dsm.tif The first link points to the landing page for the entire data release, which includes links to pages of the various data files. The second link is for accessing this digital surface model raster via cloud-based storage and can be used to download the data or for cloud-based queries. None. This dataset is provided by USGS as a public service. 20260424 Schwid, Maxwel. F U.S. Geological Survey Hydrologist Mailing and Physical

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Portland Oregon 97204 United States 503-758-5589 gs-w-or_sciencebase@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998 local time