Get Data

DOWNLOADING DATA VIA HTTPS

To learn more about Earthdata Login and to register for an account, please see How to Register with Earthdata Login. Once you have logged in, data can be downloaded via a Web browser, command line, or client. For help with downloading data, please see Options Available for Bulk Downloading Data from HTTPS with Earthdata Login.

HTTPS

IceBridge Portal: Tool to visualize, search, and download IceBridge data.
Earthdata Search: NASA's newest search and order tool for subsetting, reprojecting, and reformatting data.
IceBridge Portal: Tool to visualize, search, and download IceBridge data.
Data Set ID:
ILAKS1B

IceBridge UAF Lidar Scanner L1B Geolocated Surface Elevation Triplets, Version 1

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.

Geographic Coverage

Parameter(s):
  • Glaciers/Ice Sheets > Glacier Topography/Ice Sheet Topography
Spatial Coverage:
  • N: 72, S: 55, E: -130, W: -156

Spatial Resolution:
  • 20 cm x 20 cm
Temporal Coverage:
  • 19 August 2009 to 21 August 2016
(updated 2017)
Temporal Resolution: 12 month
Data Format(s):
  • Binary
  • XML
Platform(s) DHC-3
Sensor(s): UAF Scanner
Version: V1
Data Contributor(s): Chris Larsen
Data Citation

As a condition of using these data, you must cite the use of this data set using the following citation. For more information, see our Use and Copyright Web page.

Larsen, C. 2010, updated 2017. IceBridge UAF Lidar Scanner L1B Geolocated Surface Elevation Triplets, Version 1. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/AATE4JJ91EHC. [Date Accessed].

Back to Top

Collapse All / Open All

Detailed Data Description

Format

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.

Background color on
File and Directory Structure

Data are available on the FTP site in the https://n5eil01u.ecs.nsidc.org/ICEBRIDGE/ILAKS1B.001/ directory. This directory is organized by date, for example /2009.08.19/ to /2016.08.21/. Folders contain LAS sequential binary files and XML files.

Background color on
File Naming Convention

The data files are named according to the following convention and as described in Table 1:

Example: 
ILAKS1B_2013_239_Malaspina.las

ILAKS1B_YYYY_NNN.AAAA.xxx

Where:

Table 1. File Naming Convention
Variable Description
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
AAAA Glacier name
.xxx Indicates file type. For example: LAS 1.2 file (.las) or XML (.xml)
Background color on
File Size

Data files range from approximately 1.3 MB to 2 GB.

XML files range from approximately 4 KB to 121 KB.

Background color on
Volume

The total data set volume is approximately 157 GB.

Background color on
Spatial Coverage

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

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 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.

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.

Background color on
Temporal Coverage

These data were collected as part of NASA Operation IceBridge funded campaigns from 19 August 2009 to 21 August 2016.

Temporal Resolution

IceBridge campaigns are conducted on an annual repeating basis. Alaska campaigns are conducted during May, June, July, August, and September.

Background color on
Parameter or Variable

The UAF Lidar Scanner 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 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.

Table 2. Parameter Description and Units
Column Description Units
1 UTM Easting Meters
2 UTM Northing Meters
3 Elevation (Height Above Ellipsoid (HAE)) Meters
Background color on

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.

Background color on

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/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.

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.

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).

Background color on
Derivation Techniques and Algorithms

Processing Steps

The following processing steps are performed by the data provider.

  1. 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.
  2. 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.

Version History

On 21 September 2012, the 2009 and 2010 data were replaced with V01.1 reprocessed data. The reprocessing involved:

  1. Identifying and correcting infrequent timing shifts wherein the laser scanner data and IMU/GPS data were misaligned by 1 or 2 integer seconds. This only concerned a small handful of files, but the effect can introduce errors on the order of 10's to 100's of meters in horizontal and vertical coordinates of the point cloud data.
  2. Applying corrected boresight angles, that is, the small angular offsets between the IMU/GPS reference frame and the laser vector. These corrections were applied to all data. The previous, incorrect boresight angles introduced errors on the order of meters to 10's of meters in the horizontal and vertical coordinates of the point cloud data.
  3. Cleaning of spurious data points that did not represent real targets or surfaces. These appear in the previous versions of these data as random, individual points far away from the surfaces being imaged.
Background color on
Sensor or Instrument Description

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.

Background color on

References and Related Publications

Contacts and Acknowledgments

Chris Larsen
Geophysical Institute
University of Alaska Fairbanks
903 Koyukuk Drive
Fairbanks, Alaska 99775, USA

Acknowledgments: 

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.

Document Information

Document Creation Date

19 December 2011

Document Revision Date

08 February 2012

16 July 2012

16 December 2014

10 June 2015

09 March 2017

No technical references available for this data set.
No FAQs or How Tos available for this data set.

Access complete Knowledge Base

Questions? Please contact:
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org