mean_elev: mean vegetation-elevation digital surface model
Hubbard, T.D., Braun, M.L., Westbrook, R.E., and Gallagher, P.E., 2011, High-resolution lidar data for infrastructure corridors, Valdez Quadrangle, Alaska: Raw Data File RDF 2011-3P, 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 Raster data set. It contains the following raster data types:
Planar coordinates are encoded using row and column
Abscissae (x-coordinates) are specified to the nearest 5
Ordinates (y-coordinates) are specified to the nearest 5
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.
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.
Provide high resolution land cover data for use in vegetation classification and analysis.
McGaughey, R.J., 2007, Fusion/LDV: Software for LIDAR data analysis and visualization: USDA Forest Service, Pacific Northwest Research Station.
Data sources used in this process:
Absolute accuracy refers to the mean vertical offset of lidar data relative to measured ground-control points (GCP) obtained throughout the lidar sampling area. Ground control points were collected by McClintock Land Associates, a licensed surveying company, to be used as control comparison with lidar elevations. Refer to the lidar delivery report and lidar QC report for more details on the accuracy of the lidar data for each delivery area, including a comparison of GCP elevations with bare-earth digital elevation model elevations. The accuracy of the mean_DSM is dependent on the accuracy of the collected lidar data. Raster cell values represent an average elevation of vegetation-classified first returns.
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.
Vertical accuracy refers to the elevation difference between measured GPS control data and lidar digital elevation models. Project specifications require the root mean square vertical offset to be less than 0.2 meters. The mean_DSM represents an average vegetation surface elevation where the vertical accuracy is a function of the accuracy of the bare-earth digital elevation model and the accuracy of lidar vegetation elevation returns. For this dataset all buildings and man-made structures were omitted from analysis. Please see the lidar QC report and delivery report for specific information about accuracy and quality of lidar data.
Lidar data have been checked for accuracy and completeness. Please refer to the lidar delivery report and lidar QC report for details about data accuracy completeness for individual delivery sets.
Lidar data have been examined to ensure that overlapping flight lines have consistent elevation values. Project specifications require that lidar consistency, measured as vertical offsets between adjacent flight lines, must average less than 0.15 meters. Refer to the lidar QC report and the lidar delivery report for statistics from consistency analyses for individual delivery sets. Flight lines have been examined to ensure that there was at least 60% sidelap and that there are no data gaps. Shaded relief, lidar slope, and bare-earth digital elevation model (DEM) images have been visually inspected for data errors such as pits, border artifacts, gaps, and shifting. All file naming conventions and formats have been checked for consistency and all grids were loaded and inspected for outlier mean vegetation height values and also inspected to ensure no cell values are less than zero.
Are there legal restrictions on access or use of the data?
- This dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys.
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