snow: Polygons representing areas of snow
Hubbard, T.D., Braun, M.L., Westbrook, R.E., and Gallagher, P.E., 2011, High-resolution lidar data for infrastructure corridors, Mount Hayes Quadrangle, Alaska: Raw Data File RDF 2011-3A, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, Alaska USA.This is part of the following larger work.
Hubbard, T.D., Koehler, R.D., and Combellick, R.A., 2011, High-resolution lidar data for Alaska infrastructure corridors: Raw Data File RDF 2011-3, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, AK USA.
This is a vector data set.
Planar coordinates are encoded using coordinate pair
Abscissae (x-coordinates) are specified to the nearest 0.000001
Ordinates (y-coordinates) are specified to the nearest 0.000001
Planar coordinates are specified in meters
The horizontal datum used is North American Datum of 1983.
The ellipsoid used is Geodetic Reference System 80.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257222.
|classed||Areas of snow with valid ground points below|
|suspected||Areas indicative of snow without valid ground points below. Snow was identified based on the patterns of the intensity returns|
Data collection was supported by funding from the Department of Natural Resources (DNR), Division of Geological & Geophysical Surveys (DGGS), the Alaska Gas Pipeline Project Office, the Office of the Federal Coordinator, and the Alaska Gasline Development Corporation (AGDC). Lidar data were collected and processed by Watershed Sciences, Inc. of Corvallis, OR. Survey data were collected by McClintock Land Associates of Eagle River, AK. Lidar data and derivative products were checked for quality, completeness, and accuracy by State of Oregon Department of Geology & Mineral Industries based in Portland, OR.
Shapefile meant to identify areas within the lidar dataset that may contain snow. Ground elevations may be less accurate in areas of snow.
The accuracy of the snow polygons is dependent on the accuracy of the collected lidar data and inspection of the bare-earth DEM's and intensity images. This shapefile is only to be used as a reference and was not evaluated for accuracy.
Horizontal accuracy is dependant on the accuracy of the collected lidar data and the interpretations made from bare-earth DEM's and intensity imagery. Therefore the accuracy can be no greater than the accuracy of the lidar. True horizontal accuracy is regarded as a product of the lidar ground footprint. Lidar is referenced to co-acquired GPS base station data that have accuracies far greater than the value of the lidar footprint. The ground footprint is equal to 1/3333rd of the above-ground flying height. The ground footprint for data collected for this project exceeds typical accuracy of ground control used to reference the lidar data (less than 0.01 meters). Project specifications require the lidar footprint to be between 0.15 and 0.40 meters. Refer to the lidar QC report and lidar delivery report for additional information on horizontal accuracy for individual delivery areas.
Snow polygons were not checked for completeness. Polygons are only meant to be used as a reference in areas where there was detectable snow cover.
Lidar DEM's and intensity images were inspected to be consistent when identifying areas of snow. See process steps for more detail.
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|Data format:||vector digital data|