This data set contains contains scanning laser altimetry data points of Alaska Glaciers acquired using the airborne University of Alaska Fairbanks (UAF) Glacier Lidar system. The data were collected as part of NASA Operation IceBridge funded campaigns.
Operation IceBridge products may include test flight data that are not useful for research and scientific analysis. Test flights usually occur at the beginning of campaigns. Users should read flight reports for the flights that collected any of the data they intend to use. Check IceBridge campaign Flight Reports for dates and information about test flights.
We kindly request that you cite the use of this data set in a publication using the following citation. For more information, see our Use and Copyright Web page.
Larsen, Chris. 2010, updated 2014. IceBridge UAF Lidar Scanner L1B Geolocated Surface Elevation Triplets, [indicate subset used]. Boulder, Colorado USA: NASA DAAC at the National Snow and Ice Data Center. http://nsidc.org/data/ilaks1b.html.
DeHavilland Otter DHC-3
UAF Glacier Lidar system
Approximately 20 cm
19 August 2009 to present
LAS 1.2 sequential binary (.las)
University of Alaska Fairbanks
903 Koyukuk Drive
Fairbanks, Alaska 99775, USA
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
This program has been supported by grants from NASA, NOAA and NSF. Current support comes from NSF Arctic Natural Sciences grant ARC-0612537 and from NASA's Operation Ice Bridge, Earth Science Project Office, Grant NNX09AP54G.
The UAF Lidar Scanner Level-1B Geolocated Surface Elevation Triplets data files are in LAS 1.2 sequential binary format. The LAS file format is a public file format for the interchange of 3-dimensional point cloud data between data users (ASPRS Standards Committee LASer (LAS) File Format Exchange Activities).
Each data file is paired with an associated XML file. XML files contain file level metadata and location, platform, and campaign information.
Data are available on the FTP site in the ftp://n5eil01u.ecs.nsidc.org/SAN2/ICEBRIDGE/ILAKS1B.001/ directory. This directory is organized by date, for example /2009.08.19/ to /2013.08.30/. Folders contain LAS sequential binary files and XML files.
The data files are named according to the following convention and as described in Table 1:
|ILAKS1B||Short name for IceBridge UAF Lidar Scanner L1B Geolocated Surface Elevation Triplets|
|YYYY||Four-digit year of data collection|
|NNN||Day of Year of acquisition|
|.xxx||Indicates file type. For example: LAS 1.2 file (.las) or XML (.xml)|
Data files range from approximately 19 MB to 2 GB.
XML files range from approximately 4 KB to 63 KB.
The total data set volume is approximately 115 GB.
Spatial coverage for the IceBridge UAF Lidar Scanner Level-1B Geolocated Surface Elevation Triplets campaigns:
Southernmost Latitude: 55° N
Northernmost Latitude: 72° N
Westernmost Longitude: 156° W
Easternmost Longitude: 130° W
The footprint on the ground of the laser shot points is on the order of 20 cm in diameter. Average spacing along path and perpendicular to the flight path is roughly 1 meter by 1 meter, subject to Height Above Ground (HAG) flown and attitude of the aircraft. Preferred HAG is 500 to 600 m. Optimal conditions result in a swath 500 to 600 m wide with 1 meter by 1 meter density.
The data are provided with Universal Transverse Mercator (UTM) eastings and northings. Easting and northing values are in UTM zones 6, 7, and 8. Geoid values are not included.
These data were collected as part of NASA Operation IceBridge funded campaigns from 19 August 2009 to the present.
IceBridge campaigns are conducted on an annual repeating basis. Alaska campaigns are conducted during May, June, July, August, and September.
The UAF Lidar Scanner Level-1B Geolocated Surface Elevation Triplets data set contains elevation measurements with UTM easting and northing.
Parameters contained in UAF Lidar Scanner Level-1B data files are described in Table 2. Column numbers 1 to 3 in Table 3 represent columns left-to-right in the data. Columns are not numbered in the data files.
|3||Elevation (Height Above Ellipsoid (HAE))||Meters|
Data are available via FTP.
LAS files can be opened using tools available from the ASPRS Lidar Data Translation Toolset Web site. See also the LAStools Web page for various tools for converting, filtering, viewing, processing, and compressing LAS format lidar data.
The UAF altimetry data are comprised of a series of point measurements on the surface of glaciers recorded from an aircraft. Each point is derived from a pulsed laser range measurement combined with aircraft Global Positioning System Inertial Measurement Unit (GPS/IMU) positioning and orientation measurements. The footprint on the ground of the laser shot points is on the order of 20 cm in diameter. Coordinates and elevation for each point are referenced in the International Terrestrial Reference Frame (ITRF00) and are accurate to within +/- 30 cm. Longitude/Latitude values are derived by projecting the ITRF coordinates into WGS 84. Easting and northing values are in UTM zones 6, 7, and 8. All vertical data are in HAE.
The GPS records the position of the aircraft every second as it flies over a glacier. The laser continually measures the distance between the aircraft and the glacier surface, and the gyroscope measures the direction the laser is pointing.
The Riegl scanner has a 60 degree beam sweep, range up to 650 m, and measures 20,000 data points per second. The IMU measures the aircraft attitude (pitch, roll, yaw, and rates about those axes) and several other measurements, all at 100 times per second. The Trimble GPS records raw, dual frequency data which is post-processed after the survey against similar data recorded at a fixed GPS base station to provide precise positioning of the aircraft. At typical aircraft speeds and heights data are collected on a roughly 1 meter by 1 meter grid along a 500 meter wide swath (UAF Glacier Lidar System Web page).
The following processing steps are performed by the data provider.
On 21 September 2012, the 2009 and 2010 data were replaced with V01.1 reprocessed data. The reprocessing involved:
The UAF lidar scanner is a laser altimetry system used for measuring surface elevation changes of glaciers throughout Alaska and western Canada. The altimetry system consists of a highly accurate GPS receiver, a laser, and a gyroscope.
The main components of the UAF lidar scanner are a Riegl LMS-Q240i scanning laser altimeter, an Oxford Technical Solutions Inertial+2 inertial measurement unit, a Trimble R7 geodetic GPS receiver, and a small form factor PC for data logging.
Kwok, R., G. F. Cunningham, S. S. Manizade, and W. B. Krabill. 2012. Arctic sea ice freeboard from IceBridge acquisitions in 2009: Estimates and comparisons with ICESat. Journal of Geophysical Research 117: C02018. doi:10.1029/2011JC007654.
GAMIT-GLOBK, MIT Department of Earth Atmospheric and Planetary Sciences (http://www-gpsg.mit.edu/~simon/gtgk/).
IceBridge Data Web site at NSIDC (http://nsidc.org/data/icebridge/index.html).
IceBridge Web site at NASA (http://www.nasa.gov/mission_pages/icebridge/index.html).
ICESat/GLAS Web site at NASA Wallops Flight Facility (http://glas.wff.nasa.gov/).
ICESat/GLAS Web site at NSIDC (http://nsidc.org/daac/projects/lidar/glas.html).
NOAA OPUS: Online Positioning User Service (http://www.ngs.noaa.gov/OPUS/).
UAF Glacier Lidar System Web page (http://www.gps.alaska.edu/chris/images/Geophysical_Institute_LiDAR/index.html).
The acronyms used in this document are listed in Table 3.
|ASCII||American Standard Code for Information Interchange|
|ASPRS||American Society for Photogrammetry and Remote Sensing|
|CIRES||Cooperative Institute for Research in Environmental Science|
|FTP||File Transfer Protocol|
|GPS||Global Positioning System|
|HAE||Height Above Ellipsoid|
|HAG||Height Above Ground|
|IMU||Inertial Measurement Unit|
|ITRF||International Terrestrial Reference Frame|
|L1||L1 is a civilian-use GPS signal broadcast on the 1575.42 MHz frequency, that currently contains the course acquisition signal used by all current GPS users. Also known as L1C.|
|L2||L2 is a civilian-use GPS signal broadcast on the 1227.6 MHz frequency. Also known as L2C.|
|LAS||Laser file format for lidar point cloud data|
|NASA||National Aeronautics and Space Administration||NOAA||National Oceanic and Atmospheric Administration|
|NSF||National Science Foundation|
|NSIDC||National Snow and Ice Data Center|
|UAF||University of Alaska Fairbanks|
|URL||Uniform Resource Locator|
|UTM||Universal Transverse Mercator|
|WGS 84||World Geodetic System 1984|
19 December 2011
08 February 2012
16 July 2012
16 December 2014