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Data Set ID:
ILAKP1B

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

This data set contains surface profiles of Alaska Glaciers acquired using the airborne University of Alaska Fairbanks (UAF) Glacier Lidar system. The data were collected as part of Operation IceBridge funded aircraft survey campaigns.

Geographic Coverage

Parameter(s):
  • Glaciers/Ice Sheets > Glacier Topography/Ice Sheet Topography
Spatial Coverage:
  • N: 59.3, S: 56.94611, E: -132.32944, W: -137.52667

Spatial Resolution:
  • Varies x Varies
Temporal Coverage:
  • 22 May 2009 to 2 June 2009
Temporal Resolution: Varies
Data Format(s):
  • Binary
  • XML
Platform(s) DHC-3
Sensor(s): UAF Profiler
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. IceBridge UAF Lidar Profiler 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/10.5067/2I5C7MQ2K6V1. [Date Accessed].

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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.

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File and Directory Structure

Data files are on the FTP site, ftp://n5eil01u.ecs.nsidc.org/SAN2/ICEBRIDGE/ILAKP1B.001/ in folders organized by date, for example /2009.05.22/ to /2009.06.02/.

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File Naming Convention

The data files are named according to the following convention and as described in Table 2:

ILAKP1B_YYYY_DOY_Aaaa.nnn

Example:

ILAKP1B_2009_153_Fairweather.las
ILAKP1B_2009_153_Fairweather.las.xml

Where:

Table 2. File Naming Convention
Variable Description
ILAKP1B Short name for IceBridge UAF Lidar Profiler L1B Geolocated Surface Elevation Triplets
YYYY Four-digit year of data collection
DOY Day of Year of acquisition
Aaaa Glacier name
nnn indicates file format, LAS (.las) or XML (.xml)
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File Size

Data files range from approximately 12 KB to 1.7 MB.

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Volume

The total data set volume is approximately 20 MB.

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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.

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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.

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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.

Table 3. Parameter Description and Units
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 ILAKP1B_2009_153_Alsek.las data file converted from the binary. The three fields in each record correspond to the columns described in Table 3.

sample data record

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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.

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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 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.

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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 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.
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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.

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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

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

13 July 2012

15 July 2015

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