hh The highest-hit DSMs represent the earth's surface with all vegetation and human-made structures included.
Hubbard, T.D., Braun, M.L., Westbrook, R.E., and Gallagher, P.E., 2011, High-resolution lidar data for infrastructure corridors, Gulkana Quadrangle, Alaska: Raw Data File RDF 2011-3O, State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys, Fairbanks, AK 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 1.000000
Ordinates (y-coordinates) are specified to the nearest 1.000000
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 terrain elevation and land cover elevation data.
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 highest-hit surface model data is partly dependant on the positional accuracy of the lidar data. Development of the highest-hit surface model involved classification of buildings and structures through automated point processing algorithms and subsequent manual inspection and editing during the ground model creation. This process served as an accuracy check of the data.
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 highest-hit DSM represents the earth's surface including vegetation points, and buildings, where the vertical accuracy is a function of the accuracy of the bare-earth digital elevation model and the accuracy of lidar vegetation returns and human-made structures. Please see the lidar QC report and lidar delivery report for specific information about accuracy and quality of lidar data, including a comparison of GCP elevations with bare-earth digital elevation model elevations.
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 grids were loaded and inspected for outlier/erroneous percent cover values. All file naming conventions and formats have been checked for consistency.
Are there legal restrictions on access or use of the data?
- The datasets are 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 express or implied warranties (including warranties of merchantability and fitness) with respect to the character, function, or capabilities of the electronic services 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, any failure thereof, or otherwise, and in no event will the State of Alaska's liability to the requester or anyone else exceed the fee paid for the electronic service or product.
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