digital surface model: A single-band, 32-bit float DSM represents surface elevations of vegetation and uncovered ground surfaces in meters with a GSD of 3.8 cm per pixel. The "No Data" value is set to -32767. The file employs LZ77 compression. orthoimage: The orthoimage is a three-band, 8-bit unsigned GeoTIFF file. The orthoimagery GSD is 1.9 cm per pixel, and the 'No Data' value is set to 256.
Willingham, A.L., and Herriott, T.M., 2020, Photogrammetry-derived digital surface model and orthoimagery of Slope Mountain, North Slope, Alaska, June 2018: Raw Data File RDF 2020-1, 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 1/298.257222101000025.
The State of Alaska funded this work. We thank helicopter pilot Tom Ratledge (Yukon Aviation) for his adaptability and precise flying during the Slope Mountain photogrammetric survey. Discussions with Katreen Wikstrom Jones and Barrett Salisbury regarding photogrammetry surveys and GNSS data processing are much appreciated. Additional support in data handling and digital products was provided by Andrew Herbst, Mike Hendricks, Kristen Janssen, and Simone Montayne.
The goal of this data release is to provide a visual and quantitative context for the stratigraphy at Slope Mountain in support of geologic and petroleum systems studies. Slope Mountain is a road-accessible, world-class outcrop of the Cretaceous Nanushuk and Torok Formations, which form oil reservoirs in recent major petroleum discoveries on the North Slope. The Slope Mountain stratigraphy records chiefly progradational sedimentation, with depositional systems extending along depositional strike toward the recent discoveries farther north, providing a valuable outcrop analog to subsurface reservoirs. Within this context, DGGS recently renewed investigations at Slope Mountain, including generation of measured sections and collection of a geochronology sample suite. The DSM and othoimagery yield a three-dimensional framework that complements prior detailed outcrop work and renders geologic and geographic constraints for ongoing and future studies.
Harris, E.E., Mull, C.G., Reifenstuhl, R.R., and Montayne, Simone, 2002, Geologic map of the Dalton Highway (Atigun Gorge to Slope Mountain) area, southern Arctic Foothills, Alaska: Preliminary Interpretive Report PIR 2002-2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.
LePain, D.L., McCarthy, P.J., and Kirkham, R.A., 2009, Sedimentology and sequence stratigraphy of the middle Albian-Cenomanian Nanushuk Formation in outcrop, central North Slope, Alaska: Report of Investigation RI 2009-1 v. 2, Alaska Division of Geological & Geophysical Surveys, Fairbanks, Alaska, United States.
The DSM and orthoimagery were 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 are not hydro-flattened in these areas. There are also small artifacts present in some tundra-covered areas. Ragged edges of the survey with many data errors are clipped from both the DSM and orthoimagery.
The three GNSS points designated as checkpoints assess the horizontal accuracy of the data products by comparing their GNSS-derived locations with their position on the orthoimage. The mean offsets (residual) are 0.62 cm in the X-direction and -1.62 cm in the Y-direction, with standard deviations of 32.21 cm (X-direction) and 97.49 cm (Y-direction) and mean absolute errors of 25 cm (X-direction) and 74.36 cm (Y-direction). A horizontal transformation of -1.3685 m in the X-direction and 0.2336 m in the Y-direction is applied. A table of checkpoints and error calculations can be found in the accompanying report.
The vertical accuracy of the DSM is evaluated by comparing the elevation values of the same three checkpoints in the photogrammetry-derived DSM to the GNSS-derived elevation values. The mean vertical offset (Z-direction) is -0.75 cm, with a standard deviation of 73.66 cm and the mean absolute error of 55.11 cm. A vertical transformation of 0.5366 m is applied.
The survey's design ground sample distance (GSD) is 1.8 cm, with a survey area of approximately 2 km2. Forty northeast-southwest-trending, near-nadir-view flight lines were flown with greater than 60% side-lap and 80% end-lap. Two additional cross-cutting near-nadir-view flight lines, as well as six oblique-view flight lines, were also flown. This data release is complete.
Ground control GNSS data were submitted to the National Geodetic Survey Online Positioning User Service (OPUS) for processing. OPUS generates position solutions based on the National Oceanic and Atmospheric Administration Continuously Operating Reference Station (NOAA CORS) Network. Three of the GNSS points were used as GCPs to calibrate the DSM and orthoimagery; the remaining three points were used as checkpoints in the accuracy assessment of the data products.
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).
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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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