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Data Set ID:
ILUTP2

IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets, Version 1

The IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets (ILUTP2) data set contains surface range values for Antarctica and Greenland derived from measurements captured using the Riegl Laser Altimeter. The data were collected by scientists working on the Investigating the Cryospheric Evolution of the Central Antarctic Plate (ICECAP) project, which is funded by the National Science Foundation (NSF) and the Natural Environment Research Council (NERC) with additional support from NASA Operation IceBridge.

Geographic Coverage

Spatial Coverage:
  • N: 90, S: 60, E: 180, W: -180

  • N: -53, S: -90, E: 180, W: -180

Spatial Resolution:
  • 25 x 25
Temporal Coverage:
  • 29 December 2008
(updated 2013)
Temporal Resolution: Varies
Parameter(s):
  • Lidar > Surface Range
Platform(s) BT-67
Sensor(s): UTIG Riegl
Data Format(s):
  • XML
  • ASCII Text
Version: V1
Data Contributor(s): Donald Blankenship, Scott Kempf, Duncan Young

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.

Blankenship, D. D., S. D. Kempf, D. A. Young, J. L. Roberts, T. van Ommen, R. Forsberg, M. J. Siegert, S. J. Palmer, and J. A. Dowdeswell. 2012, updated 2013. IceBridge Riegl Laser Altimeter L2 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/JV9DENETK13E. [Date Accessed].

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Detailed Data Description

Format

The data files are in space-delimited ASCII text format. Each data file is paired with an associated XML file. The XML files contain location, platform, and instrument metadata.

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File and Directory Structure

Data are available on the HTTPS site in the https://n5eil01u.ecs.nsidc.org/ICEBRIDGE/ILUTP2.001/ directory. Within this directory, the folders are organized by date, for example /2008.12.29/ to /2013.01.22/. Folders contain ASCII (.txt) and XML (.xml) files.

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File Naming Convention

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

File name examples: 
ILUTP2_2013022_ICP5_JKB2h_F26T04a_srfelv.txt
ILUTP2_2013022_ICP5_JKB2h_F26T04a_srfelv.txt.xml

ILUTP2_YYYYDOY_AAAN_JKBna_Xnna_srfelv.xxx

Where:

Table 1. File Naming Convention
Variable Description
ILUTP2 Short name for IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets
YYYY Four-digit year of survey
DOY Day of year of survey
AAAN Geographic area
JKBna Host platform
Xnna Geographic track line
srfelv Surface range
xxx Indicates ASCII text file (.txt), or or XML file (.xml)
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File Size

The data files range from approximately 2 KB to 2.5 MB.

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Volume

The entire data set is approximately 321 MB.

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Spatial Coverage

Spatial coverage for the Riegl Laser Altimeter data includes Greenland and Antarctica. This represents the coverage noted below.

Greenland:
Southernmost Latitude 59° N
Northernmost Latitude: 83° N
Westernmost Longitude: 74° W
Easternmost Longitude: 12° W

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

Figure one shows spatial coverages for Antarctica by campaign year.
Figure 1. Antarctic Temporal and Spatial Coverage

Spatial Resolution

The effective footprint of the laser data is 25 m along track by 1 meter across track.

Projection and Grid Description

Referenced to WGS-84 Ellipsoid, ITRF-2008.

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Temporal Coverage

These data were collected as part of ICECAP, NSF, NERC, and Operation IceBridge funded campaigns from 29 December 2008 to the present.

Temporal Resolution

IceBridge campaigns are conducted on an annual repeating basis. Arctic and Greenland campaigns are conducted during March, April, and May, and Antarctic campaigns are conducted between October and February.

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Parameter or Variable

Parameter Description

The Riegl Laser Altimeter L2 files contain fields as described in Table 2.

Table 2. Parameter Description
Parameter Units
Year UTC
Day of Year UTC
Second of day UTC
Longitude Angle, WGS-84 Degrees
Latitude Angle, WGS-84 Degrees
Laser Derived Surface Range (WGS-84, ITRF2005) Meters

Missing values have been replaced by nan.

Horizontal positions represent aircraft location at the time of the observation.

Sample Data Record

Shown below are the first ten data records from the data file: ILUTP2_2013013_ICP5_JKB2h_F20T01a_srfelv.txt

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Software and Tools

No special tools are required for the ASCII text files.

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Data Acquisition and Processing

Data Acquisition Methods

The data were collected using a Riegl LD90-3800-HiP-LR combined with a range of GPS receivers and Inertial Measurement Unit (IMU) systems, mounted in a DC-3T (Basler BT-67) survey aircraft. Typical survey heights were 800 meters above the ice surface. Typical survey speeds were 90 meters/second. Pointing biases were recovered from aircraft crossovers.

Positioning and orientation for Antarctica 2009 came from loosely coupled joint Precise Point Position (PPP)/inertial solutions using an OEM-4 GPS receiver and a Honeywell HG1700/AG58 IMU. In 2010-11, positioning came from PPP solutions on a Javad GPS receiver, while orientation real time output from a Honeywell H-764 EGI (s/n #6038) provided by Danish Technical University as part of the IceGrav project. Positioning and orientation for Antarctica 2011 and 2012, and the 2011 Greenland field season came from loosely coupled joint PPP/inertial solutions using an OEM-4 GPS receiver and an iMAR FSAS IMU. Some flights during Greenland 2011 had corrupted IMU data, and thus are unavailable. See Young et al. 2014 for details of data acquisition and calibration, and see the granule metadata for specific combination used.

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Derivation Techniques and Algorithms

Trajectory and Attitude Data

Except for the 2010 field season, trajectory information was derived using Waypoint Inertial Explorer loosely coupled PPP/IMU processing. See product IceBridge GPS/IMU L1B Primary Position and Attitude Solution (IPUTG1B) and Young et al. 2014 for details.

Processing Steps

Cloud filtering was performed by passing only continuous sections 20 meters long, with jumps between samples of 2 meters rejected. Ranges of less than 150 meters were also rejected. Default ranges where a surface was not detected by the laser ranger were -1 meters. Range vectors were transformed into elevations through the vector algebra reviewed in Koks, 2008.

Version History

On 05 July, 2013, the V01 2009, 2010, and 2011 Antarctica data were replaced by V01.1. V01.1 data files were revised in the Seconds field and the Laser Derived Surface field.

Error Sources

The primary sources of errors are:

  • the pointing biases, in particular a coupling between the pitch bias and the range bias
  • the limitation on the along track resolution, especially in rough areas
  • interflight biases due to unmodelled tropospheric delays in the PPP GPS solutions

The net error is approximately 12 cm.

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Sensor or Instrument Description

The instrument has been used and validated in previous field campaigns (Young et al. 2014). The instrument is a Riegl LD90-3800-HiP-LR distance meter, with a 3.5 mW diode laser operating at 905 nm. The Laser Altimeter System (LAS) acquires measurements at 2000 Hz, with a range resolution of 2 mm and ground spot width of approximately 1 m. For each block of 575 pulses, the greatest range is recorded, along with the standard deviation and maximum amplitude of the detected pulse echoes. Samples were time stamped using a 100 kHz counter timer, along with a precise timing signal from GPS clock. Typical point separation on the ground was 21–23 m, as expected for a target ground speed of 90 m-s-1. The maximum range of the system is 1500 m over ice.

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References and Related Publications

Contacts and Acknowledgments

Donald D. Blankenship, Duncan A. Young, and Scott D. Kemp
University of Texas at Austin
Institute for Geophysics
Austin, TX, 78759-8500

Jason L. Roberts and Tas van Ommen
Australian Antarctic Division
Kingston, Tasmania
and 
Antarctic Climate and Ecosystems CRC 
University of Tasmania
Hobart, Tasmania

Martin J. Siegert
Faculty of Natural Sciences
The Grantham Institute for Climate Change
Imperial College
London, UK

Rene Forsberg
National Space Institute
Danish Technical University
Copenhagen, Denmark

Steven J. Palmer
Department of Geography
University of Exeter
Exeter, UK

Julian A. Dowdeswell
Scott Polar Research Institute
University of Cambridge
Cambridge, UK

Acknowledgements: 

University of Texas Icebridge altimetry data was sponsored by grants NNX09AR52G, NNG10HP06C – ARRA, and NNX11AD33G. The altimetry acquisition piggybacked in Antarctica on ICECAP and GIMBLE (sponsored by NSF grants PLR-0733025 and PLR-1043761, UK NERC grant NE/D003733/1 to the University of Edinburgh, Australia's ACE-CRC, AAD project 3103 and 4077), and in Greenland on IPEV project DATACO, and GrOGG (sponsored by UK NERC grant NE/H020667 to the Scott Polar Research Institute). The Danish Technical University provided the Embedded GPS/INS (EGI) Intertial Navigation System (INS) used in the 2010-2011 field season. See Support: Funding: and Institutions: fields in granules for specific information for each file.

Document Information

Document Creation Date

24 March 2015

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