Point-cloud data - all returns - classified: Classified (ASPRS standard) lidar attributes for all returns Point-cloud data - ground returns - classified: Classified (ASPRS standard) lidar attributes for ground returns LAS index file: Vector data which serves as the index illustrating the spatial location of point cloud (LAS) bin delineation Raster index: Vector data which displays the project boundary Hydro-flattened waterbody polygons: Vector data depicting water bodies (includes lakes, canals and rivers) Bare-earth digital terrain models: A model depicting the earth's surface with all vegetation and human-made structures removed Highest-hit digital surface models: A model depicting the earth's surface with all vegetation and human-made structures included Vegetation digital surface models: A model depicting the above-ground height of the vegetation Lidar intensity images: A grayscale image, similar to an orthophoto, which displays 0-255 grayscale values according to the relative reflectivity (based on lidar return intensity) of objects on the ground Hillshade images: A grayscale image model created from the bare-earth digital elevation models. It is meant to mimic the hypothetical illumination of the surface according to a specified azimuth and altitude for the sun
Hubbard, T.D., Wolken, G.J., Stevens, D.S.P., and Combellick, R.A., 2013, High-resolution lidar data for the Whittier area, Passage Canal, and Portage Lake, Alaska: Raw Data File RDF 2013-3, Alaska Division of Geological & Geophysical Surveys, Fairbanks, AK, USA.
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 North American Datum of 1983.
The semi-major axis of the ellipsoid used is 6378137.
The flattening of the ellipsoid used is 1/298.257222101.
Sequential alpha numeric values that were automatically generated to uniquely identify each LAS bin
Project boundaries and encompassing USGS 1:63360 quadrangles define the extent of each raster file. USGS quadrangle names (case may vary) are used in this file and throughout the publication to indicate the spatial location of individual raster files.
|Range of values|
|Units:||meters above sea level|
|Island in River||polygon which displays the extent and location of an island in a river|
|Lake||polygon which displays the extent and location of a lake|
|Passage Canal||polygon which displays the extent and location of Passage Canal|
|River||polygon which displays the extent and location of a river|
Financial support for this work came from State of Alaska capital-project funding. The authors are grateful for support from several staff members of the Division of Geological & Geophysical Surveys. Jim Weakland helped process data and create the hillshade images; Lauren Southerland helped organize the data for distribution; Susan Seitz created the programming by which the data are offered online; Simone Montayne assisted with metadata; and Ken Woods manages data on the server.
In support of geologic mapping and hazards evaluation in and near Whittier, Alaska, the Division of Geological & Geophysical Surveys (DGGS) acquired, and is making publicly available, lidar (light detection and ranging) data for an area along Passage Canal, Portage Lake, and Portage Glacier Highway. Data will serve multiple purposes but were primarily collected to map geology and evaluate potential geologic hazards. Steep slopes with poor access, combined with dense vegetation and a thick moss ground-cover that obscures the bedrock surface, make the use of lidar one of the most effective ways to map the geology and evaluate unstable slopes and other hazards.
Staff, DGGS, 2013, Engineering Geology FY13 project descriptions: Annual Report AR 2012-C, Alaska Division of Geological & Geophysical Surveys, Fairbanks, AK, USA.
LiDAR flight lines have been examined to ensure that there was at least 60% sidelap, there are no gaps between flight-lines, and overlapping flight-lines have consistent elevation values. Shaded relief images have been visually inspected for data errors such as pits, border artifacts, gaps, and shifting. The data was examined at a 1:2000 scale. WSI submitted the data to the State of Oregon Department of Geology and Mineral Industries (DOGAMI) for independent quality control analysis. After addressing any concerns from DOGAMI, WSI submitted the revised data set to DGGS along with a technical report describing details about the lidar acquisition, accuracy, and quality. DOGAMI also provided a separate report summarizing their methodologies and the results of quality control checks. Both reports are available via the DGGS website.
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. The values, tests, and processing methods used by WSI and DOGAMI to ensure relative accuracy are described in the accompanying delivery and quality control reports.
Vertical accuracy was assessed by comparing GPS survey collected by McClintock Land Associates with lidar digital elevation models to expose offsets. Quality control analysis performed by DOGAMI indicate that the data complies with project specifications (maximum root mean square vertical offset - 0.20 meters). Please see the lidar QC report and lidar delivery report for statistics from vertical accuracy analysis.
The pulse density distribution varies throughout the study area. Areas below 1,600 feet in elevation, including the City of Whittier, were collected at a higher pulse density (greater or equal to 8 pulses/square meter), with areas above 1,600 feet in elevation collected at greater than or equal to 4 pulses/square meter. The WSI delivery report provides additional information about the lidar pulse density and distribution. Real time kinematic ground survey data (used for absolute vertical adjustment) is available in Appendix A of the delivery report. Aircraft flight-lines (trajectory files) were supplied to DOGAMI for quality control but are not included as a component of this publication.
Data consistency varies slightly throughout the project area with higher errors in areas of steep terrain. The tests and processing methods used by WSI and DOGAMI to ensure data consistency are described in the accompanying delivery and quality control reports.
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).
- 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 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.
DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (firstname.lastname@example.org), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.
|Data format:||Shapefiles, LAS files, Esri GRID files, and GeoTIFF files|