digital surface model: The DSM is a 1-band, 32-bit floating point integer raster file (file format GeoTIFF) with a GSD of 53 cm. DSM raster cell values represent elevation values at any given point. NoData values have been set to -3.40282346639e+038. The uncompressed file size is 2.16 GB. orthomosaic: The orthomosaic is a 3-band, 8-bit unsigned integer raster file (red/green/blue; file format GeoTIFF) with a GSD of 26 cm (fig. 3A). NoData values for each band have been set to 0. The file employs Lempel-Ziv-Welch (LZW) compression and total uncompressed file size is 3.19 GB. smoothed digital surface model: The smoothed DSM is a 1-band, 32-bit floating-point integer raster file (file format GeoTIFF) with a GSD of 53 cm. This DSM was created from a smoothed 3D mesh, rather than a dense point cloud. 3D mesh creation and subsequent smoothing were done in Agisoft Metashape. Smoothing here removes much of the inherent low-noise in surface features that exist in the normal DSM. DSM raster cell values represent elevation values at any given point. NoData values have been set to -3.40282346639e+038. The uncompressed file size is 1.42 GB. dsm hillshade: The DSM hillshade is a 3-band, 8-bit unsigned integer raster file (red/green/blue; file format GeoTIFF) with a GSD of 53 cm. It represents hillshading of the unsmoothed DSM raster. NoData values have been set to 255. The file employs LZW compression. The hillshade was produced using the Image Analysis tools within ArcGIS Desktop (ArcMap 10.4). The uncompressed file size is 1.62 GB.
Escarzaga, Stephen, Kinsman, N.E.M., and Overbeck, J.R., 2020, Photogrammetric digital surface models and mosaiced orthoimagery for Barter Island, Alaska: Raw Data File RDF 2020-6, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.Online Links:
This is a raster data set.
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 World Geodetic System of 1984.
The ellipsoid used is WGS 84.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257223563000025.
This project is supported and monitored by the National Oceanic and Atmospheric Administration Cooperative Science Center for Earth System Sciences and Remote Sensing Technologies (NOAA-CESSRST) under the Cooperative Agreement Grant #NA16SEC4810008. The authors would like to thank The City College of New York, NOAA-CESSRST (aka CREST) program and NOAA Office of Education, Educational Partnership Program for full fellowship support of Stephen M. Escarzaga. Stephen M. Escarzaga would like to thank his advisor Craig Tweedie, NOAA mentors Nicole Kinsman, Jon Sellars, Jason Woolard with the National Geodetic Survey, and Ann Gibbs with the Pacific Coastal and Marine Science Center of the USGS for their guidance and contributions to this work. Additional acknowledgments for technical guidance go to Jeff Sloan (USGS), John Warrick (USGS), Ben Jones (USGS), Tahzay Jones and Chad Hults (NPS), Tom Noble, Gennady Gienko (UAF), and Mike R. James (Lancaster University). 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 funding agency or the U.S. Government. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Government.
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Alaska's extensive shorelines are incompletely mapped and poorly monitored for the evaluation of coastal dynamics. This publication was generated to support the Alaska Division of Geological & Geophysical Surveys Coastal Hazards Program. The DGGS Coastal Hazards Program is engaged in ongoing investigations that will expand our understanding of how the coastline has evolved and how it will respond to hazardous events and long-term changes and is dedicated to fostering scientific partnerships that will improve the quality and quantity of the critical baseline data that are necessary to fuel informed decision-making throughout the state.
Ground control points (GCPs) were supplied by the USGS Pacific Coastal & Marine Science Center from field reconnaissance on September 4, 2014 and September 18, 2016 with an Ashtech Z-Extreme GNSS system. A subset of 200 GCPs were used to evaluate these photogrammetric products, with 100 used to determine a mean vertical offset (as control) and 100 to determine residual error after vertical transformation (as checkpoints). Of this subset, only two GCPs were photo-identifiable. All products were visually inspected for data errors such as pits, border artifacts, and shifting.
Due to the lack of photo-identifiable GCPs, no horizontal transformation has been applied to the data. However, in the two locations where these GCPs exist, the orthomosaic showed an estimated 20 cm and 25 cm offset respectively in the Easting direction.
Vertical accuracy was determined for both the smoothed and unsmoothed DSMs. Accuracies were determined by calculating the mean vertical offset between DSMs and 100 GCPs, reducing this mean offset to zero by applying a vertical transformation and then determining a vertical Root Mean Square Error (RMSEz) for the transformed surfaces using the 100 checkpoints. The unsmoothed DSM had a mean vertical offset of +5 cm, and the final unsmoothed DSM had an RSMEz of 13.7 cm with +/- one standard deviation of 11.3 cm; 95% of checkpoints fell within 26 cm. The smoothed DSM had a mean vertical offset of +8 cm and the final smoothed DSM had an RMSEz of 13.3 cm with +/- one standard deviation of 8.5 cm; 95 percent of checkpoints fell within 28 cm. A table of checkpoints and errors is provided in the accompanying report.
Due to the orientation and QA/QC of raw images, there is a stript of data missing from both the orthomosaic and DSM on the west side of the island. This data release is complete.
The tests and processing methods used to ensure data consistency are described in the accompanying report.
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RDF 2020-6
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| Data format: | imagery |
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| Network links: |
<http://doi.org/10.14509/30456> |
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