IceBridge UAF Lidar Profiler L1B Geolocated Surface Elevation Triplets
This data set contains surface elevation profiles 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.
Table of Contents
- Contacts and Acknowledgments
- Detailed Data Description
- Data Access and Tools
- Data Acquisition and Processing
- References and Related Publications
- Document Information
Citing These Data
The following example shows how to cite the use of this data set in a publication.
Larsen, Chris. 2010. IceBridge UAF Lidar Profiler L1B Geolocated Surface Elevation Triplets, [list dates of data used]. Boulder, Colorado USA: NASA Distributed Active Archive Center at the National Snow and Ice Data Center. Digital media. http://nsidc.org/data/ilakp1b.html.
Overview
| Piper Supercub (PA-12) | |
UAF Glacier Lidar system |
|
Alaska |
|
| Approximately 20 cm |
|
22 May 2009 to 02 June 2009 |
|
| n/a |
|
Elevation |
|
LAS 1.2 sequential binary |
|
Metadata Access |
|
Data Access |
1. Contacts and Acknowledgments
Investigator(s) Name and Title
Chris Larsen
Geophysical Institute
University of Alaska Fairbanks
903 Koyukuk Drive
Fairbanks, Alaska 99775, USA
Technical Contact
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
e-mail: nsidc@nsidc.org
Acknowledgements
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.
2. Detailed Data Description
Format
The UAF Lidar Profiler 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. See ASPRS Standards Committee LASer (LAS) File Format Exchange Activities.
File and Directory Structure
Data are available on the n4ftl01u.ecs.nasa.gov FTP site in the /SAN2/ICEBRIDGE_FTP/ directory. Within this directory, there is one subdirectory as described in Table 1.
| Directory | Description |
|---|---|
| /ILAKP1B_UAFprofile_v01/2009_AK_UAF/ | 2009 UAF Profiler Level-1B Geolocated Surface Elevation Triplets data |
File Naming Convention
The data files are named according to the following convention and as described in Table 2:
Aaaa_yyyy_nnn.las
File name example: MtFairweather_2009_153.las
Where:
| Variable | Description |
|---|---|
| Aaaa | Glacier name |
| yyyy | Four-digit year of data collection |
| nnn | Day of Year of acquisition |
| .las | indicates LAS file format |
File Size
Data files range from approximately 12 KB to 1.7 MB.
Volume
The total data set volume is approximately 13 MB.
Spatial Coverage
Spatial coverage for the IceBridge UAF Lidar Profiler Level-1B Geolocated Surface Elevation Triplets campaigns:
Southernmost Latitude: 56.95° N
Northernmost Latitude: 59.30° N
Westernmost Longitude: 137.53° W
Easternmost Longitude: 132.33° W
Spatial Resolution
The footprint on the ground of the laser shot points is on the order of 20 cm in diameter. Average spacing along path is roughly 1.2 meters, subject to Height Above Ground (HAG) flown and and attitude of the aircraft. Preferred HAG is 500 to 600 m.
Projection and Grid Description
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.
Temporal Coverage
These data were collected as part of NASA Operation IceBridge funded campaigns from 22 May 2009 to 02 June 2009.
Temporal Resolution
IceBridge campaigns are conducted on an annual repeating basis. Alaska campaigns are conducted during May, June, July, August, and September.
The data points along the flight path are collected from a profiling laser at a rate of 20 Hz.
Parameter or Variable
The UAF Lidar Profiler Level-1B Geolocated Surface Elevation Triplets data set contains elevation measurements with UTM easting and northing.
Parameter Description
Parameters contained in UAF Lidar Scanner Level-1B data files are described in Table 3. Column numbers 1 to 3 in Table 3 represent columns left to right in the data. Columns are not numbered in the data files.
| Column | Description | Units |
|---|---|---|
| 1 | UTM Easting | Meters |
| 2 | UTM Northing | Meters |
| 3 | Elevation (Height Above Ellipsoid (HAE)) | Meters |
Sample Data Record
Below is an ASCII format excerpt of the Alsek_2009_153.las data file converted from the binary. The three fields in each record correspond to the columns described in Table 3.
3. Data Access and Tools
Data Access
Data are available via FTP.
Software and Tools
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.
4. Data Acquisition and Processing
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 and 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.
A profile transect of points along the flight path is collected from the laser system at a pulse rate of 20 Hz. Average spacing along path is roughly 1.2 meters, subject to HAG flown and wind, turbulence, and maneuvering. Preferred HAG is 500 to 600 m.
Data Acquisition Methods
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.
Derivation Techniques and Algorithms
Processing Steps
The following processing steps are performed by the data provider.
- All GPS processing of the aircraft position uses L1 frequency 1575.42 MHz and L2 frequency 1227.6 MHz data recorded at 5 Hz, processed with the TRACK GPS differential phase kinematic positioning program, a module of the GAMIT/GLOBK software programs from the Department of Earth Atmospheric and Planetary Sciences, MIT. For further information on TRACK, see http://geoweb.mit.edu/~tah/track_example.
- GPS base station coordinates are found using Online Positioning User Service (OPUS). For further information on OPUS, see http://www.ngs.noaa.gov/OPUS/. The kinematic processing and the laser shot point coordinates are referenced to these base station coordinates.
Sensor or Instrument Description
The UAF lidar profiler is used for measuring surface elevation changes of glaciers throughout Alaska and western Canada. The system consists of a highly accurate GPS receiver, a laser profiler, and a gyroscope. Combining data from these instruments, elevation profiles of the surface of the glacier are created that are accurate to better than half a meter.
5. References and Related Publications
Related Data Collections
Related Web Sites
- 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).
6. Document Information
Acronyms and Abbreviations
The acronyms used in this document are listed in Table 4.
| Acronym | Description |
|---|---|
| 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 |
| Level-1B | Processing Level-1B |
| 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 |
Document Creation Date
19 December 2011
Document Revision Date
08 February 2012
13 July 2012
Document URL
http://nsidc.org/data/docs/daac/icebridge/ilakp1b/index.html
