digital surface model: DSMs represent surface elevations of all surfaces, including vegetation, vegetation-free land, bridges, buildings, etc. The Yukon River (not including tributaries and lakes within the study area) was hydro flattened using standardized hydro flattening workflow in ArcMap (McLean, 2018) with a resulting elevation change from 85.1 m in the east to 81.1 m in the west within the DSM boundary (east-west streamflow direction). The DSM is a single-band, 32-bit float GeoTIFF file, with a ground sample distance (GSD) of 0.47 m. No Data value is set to -3.40282306074e+038.
Wolken, G.J., and Wikstroem Jones, Katreen, 2019, Photogrammetry-derived digital surface model and orthoimagery of areas near the Dalton Highway, Yukon River Crossing, Alaska: Raw Data File RDF 2019-4, 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 1/298.257222101000025.
These data products were funded by the Alaska Department of Transportation & Public Facilities, and Alaska Department of Natural Resources, Division of Geological & Geophysical Surveys. We thank Clearwater Air for their aviation expertise and contribution to these data products.
The data release is one of a series of Alaska Division of Geological & Geophysical Surveys (DGGS) publications to present elevation data over Yukon River Crossing in support of landslide hazard mapping.
The DSM and orthoimagery have been visually inspected for data errors such as pits, border artifacts, and shifting. The end-user should be aware that pits and peaks are present in areas of some small water bodies, such as lakes and ponds, and that DSM data have not been hydro-flattened in these areas.
The horizontal accuracy was assessed by comparing the locations of six GNSS-derived control points with their locations in the orthoimagery. The initial mean offset (residual) was +1.35 m in the X-direction and -0.03 m in the Y-direction, with a standard deviation of 0.47 m (0.65 m, Y-direction) and a mean-absolute-error (MAE) of 1.35 m (0.46 m, Y-direction). A horizontal transformation of -1.35 m in X-direction was applied because horizontal offset was identified above the pixel scale of the DEM (i.e., 0.47 m GSD). The final horizontal accuracies were based on the same control points as checkpoints and are described in table 1 of the accompanying report. > Check Point,Horizontal Offset X (m),Horizontal Offset Y (m),Easting (X),Northing (Y),Elevation (m) > YK-01,0.64,-1.16,385213.56,7303075.69,571.24 > YK-03,0.29,0.74,376208.41,7309124.78,95.28 > YK-04,-0.66,0.53,370524.83,7315054.63,160.34 > YK-05,0.69,-0.22,371052.7,7314408.97,152.61 > YK-06,-0.12,-0.11,374073.81,7311526.54,105.19 > YK-07,0.84,0,375527.33,7310228.21,96.83 > Mean,0.28,-0.04 > Std. Dev,0.58,0.67 > Range,1.5,1.9 > MAE,0.54,0.46
The DSM was vertically controlled by comparing the elevation values of 9,794 points collected in transects along the highway on a paved surface in the photogrammetry-derived DSM to the elevation values at the same location in a lidar-derived dataset (bare earth DEM) collected in May 2011 (Hubbard and others, 2011). The initial mean vertical offset was -1.60 m with a standard deviation of 0.38 and Root-Mean-Square-Error of 1.64 m. A vertical transformation of +1.60 m was applied. The final DSM vertical accuracy was evaluated with an additional 10,469 checkpoints and has a mean vertical residual of 0.02 m with a standard deviation of 0.41 m and an RMSE of 0.41 m.
The aerial photographic survey resulted in approximately 60 percent side lap and 80 percent end lap coverage, with an above ground-level flying height of 1,100-2,000 m, which resulted in 4,922 photos with 0.24 m ground sample distance (GSD). The total area surveyed was approximately 360 km2. This data release is complete.
To evaluate data consistency, ground control checkpoints were collected (September 21, 2016) as rapid-static occupations (15 min) with a Trimble R8 GNSS receiver. A Trimble R7 GNSS receiver with Zephyr-2 antenna was deployed near the center of the study area and was used as horizontal and vertical control for checkpoint baseline corrections.
Are there legal restrictions on access or use of the data?
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