Data Set ID:

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

This data set contains scanning laser altimetry data points of Alaskan glaciers and parts of East and West Antarctica acquired by the airborne University of Alaska Fairbanks (UAF) Glacier Lidar system. The data were collected as part of NASA Operation IceBridge funded campaigns.

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


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Geographic Coverage

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

  • N: -53, S: -90, E: 180, W: -180

Spatial Resolution:
  • 20 cm x 20 cm
Temporal Coverage:
  • 19 August 2009 to 18 December 2017
(updated 2018)
Temporal Resolution: 1 year
Data Format(s):
  • XML
  • Binary
Platform(s) BT-67, 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 2018. 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: [Date Accessed].

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Detailed Data Description


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, which contains additional metadata.

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File and Directory Structure

Data are available via HTTPS in the following directory:

Within this directory, the folders are named for each year, month, and day of the data collection, for example: /2009.08.19/.

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File Naming Convention

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



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 Three-digit day in acquisition year
AAAA Glacier name (optional; only applies to Alaska campaigns)
.xxx Indicates file type. For example: LAS 1.2 file (.las) or XML (.xml)
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File Size

Binary files range from approximately 1.3 MB to 2 GB. The total binary file volume is approximately 224 GB.

XML files range from approximately 4 KB to 121 KB. The total XML file volume is approximately 0.01 GB.

The total data set volume is approximately 224 GB.

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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

Southernmost Latitude: 90° S
Northernmost Latitude: 53° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E

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 m by 1 m, 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 of 500 to 600 m width with a 1 m by 1 m density.

Projection and Grid Description

The data are provided with Universal Transverse Mercator (UTM) eastings and northings. Geoid values are not included.

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Temporal Coverage

19 August 2009 to 18 December 2017

Temporal Resolution

IceBridge campaigns are conducted on an annually repeating basis. Alaska campaigns are conducted during May, June, July, August, and September, and Antarctic campaigns are conducted during October and November.

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Parameter or Variable

This data set contains elevation measurements with UTM easting and northing.

Parameter Description

Parameters contained in the data files are described in Table 2. Column numbers 1 to 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
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Software and Tools

LAS files can be opened using tools available from the ASPRS Lidar Data Translation Toolset website. See also the LAStools web page for various tools for converting, filtering, viewing, processing, and compressing LAS format lidar data.

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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 m by 1 m grid along a 500 meter wide swath (UAF Glacier Lidar System web page).

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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
  2. GPS base station coordinates are found using Online Positioning User Service (OPUS). For further information on OPUS, see 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.
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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.

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References and Related Publications

Contacts and Acknowledgments

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


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

21 November 2017

21 May 2018

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