orthoimagery: Orthoimages contain 3-band, 8-bit, unsigned raster data (red/green/blue; the No Data value is set to 0. The file employs Lempel-Ziv-Welch (LZW) compression. Light exposures in the orthoimages are a result of daily weather conditions, which ranged from low cloud cover, rain, and full sun; digital surface model: The single-band, 32-bit float DSMs represent surface elevations of buildings, vegetation, and uncovered ground surfaces. The No Data value is set to -32767. The file employs LZW compression; DSM hillshade: The single-band, 8-bit, unsigned integer rasters represent hillshading of the DSM. The No Data value is set to 255. The file employs LZW compression and has the same spatial resolution as the DSM. The hillshade was produced using Blue Marble Geographic's Global Mapper GIS application; orthoimagery hillshade combination raster: The orthoimagery hillshade combination rasters contain 3-band, 8-bit, unsigned raster data and represents a hillshade-tinted orthoimage. The No Data value is set to 0. The file employs LZW compression. The file was produced with ESRI's ArcGIS using Raster Function templates. This file has the same spatial resolution as its originating DSM; community data extent polygon file: One polygon shapefile is available that shows the data extent and data attributes for all 26 communities; Note: this file is provided in NAD 1983, UTM Zone 3 coordinates.
Overbeck, J.R., Hendricks, M.D., and Kinsman, N.E.M., 2016, Photogrammetric digital surface models and orthoimagery for 26 coastal communities of western Alaska: Raw Data File RDF 2016-1, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.
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 North American Datum of 1983.
The ellipsoid used is GRS 80.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257222101.
Field: Description community: Community name code: 3 digit airport code for community ortho_gsd: Orthoimage ground sample distance (gsd), that is, raster cell size, in meters dsm_gsd: DSM ground sample distance (gsd), that is, raster cell size, in meters vert_shift: Vertical shift, in meters Rmse: Root mean square error (RMSE) in meters Num_pts: Number of points used to calculate RMSE Utm_zone: UTM zone of the delivered data ortho_gb: Size, in gigabytes, of orthoimage raster file dsm_gb: Size, in gigabytes, of DSM raster file dsm_hs_gb: Size, in gigabytes, of DSM hillshade raster file tint_gb: Size, in gigabytes, of orthoimage hillshade tint raster file
This publication is funded with qualified outer continental shelf oil and gas revenues by the Coastal Impact Assistance Program, U.S. Fish and Wildlife Service, U.S. Department of the Interior. 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 U.S. Government. Mention of trade names or commercial products does not constitute their endorsement by the U.S. Government.
The State of Alaska Division of Geological & Geophysical Surveys acquired photogrammetric digital surface models (DSMs) and co-registered orthorectified aerial images (orthoimages) for the west coast of Alaska in support of coastal vulnerability mapping efforts. For the purposes of open access to elevation and orthoimagery datasets in coastal regions of Alaska, this collection is being released as a Raw Data File with an open end-user license.
Community-specific data quality and reference information can be found in table 1 of the accompanying report. Known anomalies within the data exist on the DSMs over water bodies; these anomalies have not been edited in this data release. Because waves in the nearshore marine or lacustrine environment move at a higher speed than photo-collection, the SfM processing technique for producing DSMs defines those points irregularly (for an example, see fig. 2 of the accompanying report).
The aerial survey was planned so flight lines and photograph frequency provided 60 percent side lap and 80 percent end lap photo coverage, with flying heights between 800 and 2,700 ft (244-823 m) resulting in 10-20 cm ground sample distance (GSD; see table 1 of the accompanying report) of the aerial photos.
The vertical accuracies of the DSMs were evaluated by comparing both the GCP elevations and checkpoint elevations with the DSM elevations separately for each non-contiguous community (with the exception of Stebbins/Saint Michael, the data are not contiguous between communities). We reduced the residual difference between GCPs and DSM pixels to zero mean using a vertical shift (see table 1). The remaining residuals were used to determine the Root Mean Square Error (RMSE) at each community, then combined to determine RMSE for the dataset as a whole. The final DSMs had a mean vertical residual of 6.2 cm with +/- one standard deviation of 5.2 cm, with 95 percent of all GCP and checkpoint residuals within 16.7 cm. The RMSE of all GCPs and checkpoints was 8.1 cm, but varied by location (see table 1).
This data release is complete.
Are there legal restrictions on access or use of the data?
- 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.
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.
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|Data format:||Shapefiles, Raster data|