ground_points: ground-classified laser returns from the lidar survey and their associated geospatial coordinates.
Hubbard, T.D., Braun, M.L., Westbrook, R.E., and Gallagher, P.E., 2012, High-resolution lidar data for infrastructure corridors, Anchorage Quadrangle, Alaska: Raw Data File RDF 2011-3L, 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 2.83
Ordinates (y-coordinates) are specified to the nearest 2.83
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 was supported by funding from the Department of Natural Resources, Division of Geological & Geophysical Surveys (DGGS) and the Alaska Gas Pipeline Project Office and the Office of the Federal Coordinator. Lidar data was collected by Watershed Sciences, Inc., Corvallis, OR, Survey data was collected by McClintock Land Associates, Eagle River, AK, Quality control check for data was done by State of Oregon Department of Geology & Mineral Industries, Portland, OR.
Provide high-resolution terrain elevation and land cover elevation data.
The American Society for Photogrammetry & Remote Sensing (ASPRS), 02092008, LAS Specification Version 1.2.
Data sources used in this process:
Absolute accuracy refers to the mean vertical offset of lidar laser point data relative to measured ground-control points (GCP) obtained throughout the lidar sampling area. The contractor used a surveying system to measure GCP's. GPS survey techniques allow surveyors to collect many precisely located GCP's which can be used as a control comparison with lidar elevations. A licensed surveyor is often able to post process GPS survey data to accuracies less than 1 cm both horizontally and vertically. Lidar 1 m grids were loaded into ArcGIS software for visual analysis. Data were examined through slope and hillshade models of bare earth returns. Both bare earth and highest hit models were examined for calibration offsets, tiling artifacts, seam line offsets, pits and birds. Please see the lidar delivery report and the lidar QC report for specific information about laser point processing and accuracy evaluation.
Horizontal accuracy refers to the ability to place laser points from multiple flight lines in the same location. Horizontal accuracy is measured as the divergence between points from overlapping flight lines. Accuracy is affected by system attitude offsets, scale and GPS/IMU drift. Manual system calibration and automated attitude calibration techniques were used to resolve divergence of data. Please see the lidar QC report and lidar delivery report for specific information about accuracy of lidar data.
Vertical accuracy refers to the elevation difference between measured GPS control data and lidar bare-earth digital elevation models. Project specifications require the root mean square vertical offset to be less than 0.2 meters. 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.
All data have been loaded and viewed to ensure completeness. LAS file headers have been scanned to ensure completeness and readability
Lidar returns have been examined to ensure that data from overlapping flight lines have consistent elevation values. Project specifications require that lidar consistency, measured as vertical offsets of data between adjacent flight lines, must average less than 0.15 meters. Flight lines have been examined to ensure that there was at least 60% sidelap and that there are no data gaps. All file naming conventions and formats have been checked for consistency. Refer to the lidar QC report and the lidar delivery report for statistics from consistency analyses of individual delivery sets.
Are there legal restrictions on access or use of the data?
- The dataset(s) is (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.
907 451-5010 (voice)
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.
|Data format:||LAS (version v.1.2)|
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You will be charged $56 per hour (11 AAC 05.010) for data processing for any staff time in excess of one hour.
DGGS is developing options to make the data available to users directly from the internet; however, it is currently only available via hard drive. There are two options for copying the data to a hard drive: (1) DGGS will purchase a brand-new, 2 TB hard drive that you will be billed for when the data is picked up or sent, OR (2) you may provide a new, unopened* (in original packaging, including shrink-wrap - *The State of Alaska IT security policy prohibits non-State resources from being connected to a State of Alaska network. Thus, only unused drives can be used.) 2 TB or larger hard drive. Upon release, the complete set of point-cloud data will be available to users in LAS 1.2 format. The point-cloud files total approximately 1.2 TB. The data will be copied onto the drive in gzip (gz) file format. DGGS recommends uncompressing this data using 7-Zip, a free program available from <http://www.7zip.org>. For all orders, please include: title and publication number.