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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.
|Data Contributor(s):||Donald Blankenship, Scott Kempf, Duncan Young|
|Metadata XML:||View Metadata Record|
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].
Detailed Data Description
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.
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
/2013.01.22/. Folders contain ASCII (.txt) and XML (.xml) files.
The data files are named according to the following convention and as described in Table 1:
File name examples:
||Short name for IceBridge Riegl Laser Altimeter L2 Geolocated Surface Elevation Triplets|
||Four-digit year of survey|
||Day of year of survey|
||Geographic track line|
||Indicates ASCII text file (.txt), or or XML file (.xml)|
The data files range from approximately 2 KB to 2.5 MB.
The entire data set is approximately 321 MB.
Spatial coverage for the Riegl Laser Altimeter data includes Greenland and Antarctica. This represents the coverage noted below.
Southernmost Latitude 59° N
Northernmost Latitude: 83° N
Westernmost Longitude: 74° W
Easternmost Longitude: 12° W
Southernmost Latitude: 90° S
Northernmost Latitude: 53° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E
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.
These data were collected as part of ICECAP, NSF, NERC, and Operation IceBridge funded campaigns from 29 December 2008 to the present.
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.
The Riegl Laser Altimeter L2 files contain fields as described in Table 2.
|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:
Software and Tools
No special tools are required for the ASCII text files.
Data Acquisition and Processing
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.
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.
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.
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.
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.
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.
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
Antarctic Climate and Ecosystems CRC
University of Tasmania
Martin J. Siegert
Faculty of Natural Sciences
The Grantham Institute for Climate Change
National Space Institute
Danish Technical University
Steven J. Palmer
Department of Geography
University of Exeter
Julian A. Dowdeswell
Scott Polar Research Institute
University of Cambridge
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 Creation Date
24 March 2015