IceBridge MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom
This data set contains products from depth sounder measurements over Greenland and Antarctica taken from the Multichannel Coherent Radar Depth Sounder (MCoRDS), and also includes multi-year composite Greenland data. The data were collected as part of NASA Operation IceBridge funded campaigns.
Operation IceBridge products may include test flight data that are not useful for research and scientific analysis. Test flights usually occur at the beginning of campaigns. Users should read flight reports for the flights that collected any of the data they intend to use. Check IceBridge campaign Flight Reports for dates and information about test flights.
NOTE: The content provided in this document represents the most complete information currently available for this data set. If you have questions not covered by this document, please contact NSIDC User Services.
Table of Contents
- Contacts and Acknowledgments
- Detailed Data Description
- Data Access and Tools
- Data Acquisition and Processing
- References and Related Publications
- Document Information
Citing These Data
The following example shows how to cite the use of this data set in a publication.
Leuschen, Carl, and Chris Allen. 2011, updated current year. IceBridge MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom, [list dates of data used]. Boulder, Colorado USA: NASA Distributed Active Archive Center at the National Snow and Ice Data Center. Digital media. http://nsidc.org/data/irmcr3.html.
Overview
| NASA Douglas DC-8 | |
CReSIS Multichannel Coherent Radar Depth Sounder (MCoRDS) |
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Antarctica: Greenland: |
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| Spatial Resolution is dependent on along-track, cross-track, and aircraft height characteristics. |
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2010 to the present, and 1995 to 2011 multi-year composite. |
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| Seasonal |
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Gridded Ice Thickness, Surface and Bottom |
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CSV, PNG, TIFF, TFW, and ESRI shapefiles. |
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Metadata Access |
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Data Access |
1. Contacts and Acknowledgments
Investigator(s) Name and Title
Leuschen, Carl, Chris Allen, Prasad Gogineni, Fernando Rodriguez, John Paden, Jilu Li
The Center for Remote Sensing of Ice Sheets (CReSIS)
Department of Electrical Engineering and Computer Science
Nichols Hall
2335 Irving Hill Road
University of Kansas
Lawrence, Kansas 66045
Technical Contact
NSIDC User Services
National Snow and Ice Data Center
CIRES, 449 UCB
University of Colorado
Boulder, CO 80309-0449 USA
phone: +1 303.492.6199
fax: +1 303.492.2468
form: Contact NSIDC User Services
e-mail: nsidc@nsidc.org
Acknowledgements
The radar depth sounder data and data products from the Center for Remote Sensing of Ice Sheets (CReSIS) have been collected on an ongoing basis since 1993 using grant funding from NASA and NSF. The most recent data were collected as part of the NSF Science and Technology Center grant (ANT-0424589) and the NASA Operation IceBridge field campaign (NNX10AT68G).
CReSIS faculty, staff, and students designed, developed, operated, and processed data from the radar systems.
2. Detailed Data Description
This data set contains products from depth sounder measurements over Greenland and Antarctica including gridded ice thickness, surface and bottom. Additional products include flightlines, boundaries, preview images, and crossover analysis.
Format
The MCoRDS Level-3 data files are in CSV, PNG, TIFF, TFW, and ESRI shapefile formats.
File and Directory Structure
Data files are organized on the FTP site, ftp://n4ftl01u.ecs.nasa.gov/SAN2/ICEBRIDGE_FTP/, as described in Figure 1.
Figure 1. Directory Structure
File Naming Convention
The MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom data files are named with a variety of variables as shown below and described in Table 1:
Example File Names:
2010_Thwaites_Thickness.png
2010_Smith_Surface.tif
2010_PineIsland_Dense_Flightlines.shp
2010_PineIsland_Crossovers.csv
2011_79N_Flightlines_Coarse.png
2011_79N_IceFreeArea_Dense.shp
1995_2011_Catchment_surface.tif.aux.xml
2010_PineIsland_Coarse_StudyArea.shp
2010_PineIsland_Coarse_Bottom.tif
2010_PineIsland_Coarse_XYZGrid.csv
Composite_Flight_lines.png
Year_Location_Description.xxx
Where:
| Variable | Description |
|---|---|
| Year | Year of data capture. Examples: YYYY 4-digit year, 1995_2011, Composite. |
| Location | Gridded bed map location. Examples: PineIsland, Thwaites, Smith, Petermann, Pete, 79N (79N Glacier). |
| Description | Data file content description. Examples: Coarse, Dense, StudyArea, IceFreeArea, Crossovers, Flightlines, Bottom, Surface, Thickness, XYZGrid, flight_lines, flightlines, cross_overs, Crossovers, crossover_analysis, bound, composite, Composite_by_year, channel, catchment. |
| .xxx | File type. .csv = Comma Separated Values text file .png = Portable Network Graphics file .tif = Tag Image Format File .tif.ovr = TIFF overview file .tif.xml = TIFF associated XML header information file .tfw = TIFF World File .tif.aux.xml = TIFF georeference metadata file .shp = ESRI shapefile (includes associated files: dbf, prj, sbn, sbx, shp.xml, shx) |
File Size
CSV text files range from approximately 32 KB to 24 MB.
PNG files range from approximately 240 KB to 848 KB.
TIFF files range from approximately 16 KB to 144 KB.
ESRI .shp files range from approximately 48 KB to 9 MB.
ESRI .dbf files range from approximately 16 KB to 12 MB.
Volume
The entire data set is approximately 449 MB.
Spatial Coverage
Spatial coverage for this data set includes Greenland and Antarctica. In effect, this represents the two coverages noted below.
Greenland:
Southernmost Latitude: 59° N
Northernmost Latitude: 83° N
Westernmost Longitude: 74° W
Easternmost Longitude: 12° E
Antarctica:
Southernmost Latitude: 90° S
Northernmost Latitude: 63° S
Westernmost Longitude: 180° W
Easternmost Longitude: 180° E
Spatial Resolution
Spatial resolution varies depending on the platform and year. See the Processing Steps section for details on grid size.
Projection and Grid Description
The flightlines are in Operation IceBridge polar stereographic projections for Greenland Standard Parallel 70° N and Longitude of the Origin 45° W, and Antarctica Standard Parallel 71° S and Longitude of the Origin 0° E.
Temporal Coverage
These data were collected as part of Operation IceBridge funded campaigns from 2010 to the present. Multi-year data collected prior to Operation IceBridge from 1995 to 2009 are from CReSIS.
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 during October and November.
Parameter or Variable
The MCoRDS L3 data set includes grids of MCoRDS L2 data for time, latitude, longitude, elevation, surface, bottom, and thickness. This data set is a merging of several data sources: radar depth sounder over multiple seasons, airborne lidar data for the ice surface, optical data for ice boundaries, and various ice surface digital elevation models for the ice surface to fill in where no lidar is available.
Parameter Description
The CSV grid files contain fields as described in Table 2.
| Parameter | Description | Units |
|---|---|---|
| X | Longitude | Degrees |
| Y | Latitude | Degrees |
| Thickness | Ice Thickness | Meters |
| Surface | Ice Surface Height | Meters |
| Bottom | Ice Bottom Height | Meters |
The CSV flightline files contain fields as described in Table 3.
| Parameter | Description | Units |
|---|---|---|
| LAT | Longitude | Degrees |
| LON | Latitude | Degrees |
| TIME | UTC Time | Seconds of day |
| THICK | Ice Thickness: Bottom minus Surface. Constant dielectric of 3.15 (no firn) is assumed for converting propagation delay into range. -9999 indicates no thickness available. | Meters |
| ELEVATION | Elevation referenced to WGS-84 Ellipsoid. | Meters |
| FRAME | Fixed length numeric field. YYYY = year, MM = month, DD = day, SS = segment FFF = frame. |
N/A |
| SURFACE | Range to Ice Surface. Actual surface height is Elevation minus this number. | Meters |
| BOTTOM | Range to Ice Bottom. Actual ice bottom height is Elevation minus this number. Constant dielectric of 3.15 (no firn) is assumed for converting propagation delay into range. -9999 indicates no thickness available. | Meters |
| QUALITY | 1 = High confidence pick 2 = Medium confidence pick 3 = Low confidence pick |
N/A |
| REAL_SURF | Used to interpolate the surface. | Meters |
| REAL_BOTT | Used to interpolate the bottom. | Meters |
Sample Data Records
Below is an excerpt from 2010 Antarctica data file 2010_SmithXYZGrid.csv. The fields in each record correspond to the columns described in Table 3.
Below is an excerpt from data file 2010-11_Pete_flight_lines.csv. The fields in each record correspond to the columns described in Table 4.
The 2010_11_Pete_Thickness.png preview image is shown below.
Below is the 2010_11_Petermann_crossover_analysis.png image.
3. Data Access and Tools
Data Access
Data are available via FTP.
Software and Tools
CSV files may be opened by any text viewing program.
PNG files may be opened using any program capable of reading Portable Network Graphics files.
TIFF files may be opened using any program capable of reading Tag Image File Format files.
Shapefiles may be opened using ESRI ArcGIS or other similar GIS software.
4. Data Acquisition and Processing
The MCoRDS Level-3 data set is a merging of several data sources: radar depth sounder over multiple seasons, airborne lidar data for the ice surface, optical data for ice boundaries, and various ice surface digital elevation models for the ice surface when coincident lidar data are not available. This data set includes grids of MCoRDS Level-2 data for time, latitude, longitude, elevation, surface, bottom, and thickness.
Data Acquisition Methods
P-3 Low Altitude
A waveform with a 1-μs duration and lower receiver gain settings is used to measure the round-trip signal time for the surface echo, while a waveform with a 10-μs duration and higher receiver gain settings is used to measure the round-trip signal time for the bed echo. The two different waveforms are used because of the large dynamic range of signal powers that are observed. The 10-μs duration and higher receiver gain settings are more sensitive to the bed echo, but the signal is generally saturated from the ice surface and upper internal layers.
DC-8 Low Altitude
The DC-8 low altitude method is the same as the low altitude P-3. However, during the first two field seasons (2009 Antarctica DC-8 and 2010 Greenland DC-8), extra antennas inside the cabin were used to detect the ice surface delay time because the Transmit Receive (TR) switches did not meet their switching time specification. The TR switches have not been fixed in subsequent field seasons, but the TR switch control signals have been set so that the surface echo is generally still detectable, although with diminished power even for very low altitudes down to 600 feet Above Ground Level (AGL).
P-3 High Altitude and DC-8 High Altitude
The dynamic range between the ice surface and ice bottom echoes is much smaller and a single high-gain and long pulse duration waveform is used to capture both echoes.
Derivation Techniques and Algorithms
Along with gridded ice thickness, surface, and bottom, the MCoRDS Level-3 data set contains flightlines, boundaries, preview images, crossover analysis, and grids.
Flightlines
Each flightline is provided in ESRI shapefile format as well as in a CSV file containing all the attributes of the flightline. Flightlines are clipped to the study extent. The fields A_SURF and A_BOTT are used to interpolate the surface and bed respectively. For 1995-2011 files, this is described as REAL_SURF and REAL_BOTT. The flightlines are in the NSIDC standard projects. See Operation IceBridge Standard Projections for Gridded Data.
For flightline information for the 1995, 1996, 1997, 1999, 2002, 2003, 2007,and 2010 Thwaites Glacier data sets, and the 2011 Greenland data sets, lines were segmented between catchment and channel to allow for optimal grid resolution for each region. Missions flown during 2002 or earlier do not contain frame or year data.
Boundaries
The boundaries were derived to define the scientific study areas for the regions based on available data. Study area boundaries are provided as ESRI shapefiles. The boundaries were used to clip flightlines and mask the final gridded products.
Preview Images
Preview maps of flightlines, thickness, surface, and bed topography are provided in PNG format for preview and initial analysis only. The images show the grids without the -9999 'NoData' mask.
Crossover Analysis
Crossover analysis files are used for error estimation and data quality check. This includes a CSV file containing the data, and a PNG image. The 2011 Greenland 79N Glacier Dense campaign includes an ESRI shapefile. No crossover analysis files are included for the multi-year 1995 to 2011 Petermann composite.
Processing Steps
The gridding process varies because of differing methods and data sources.
Grids
Grid files are masked GeoTIFF rasters containing values for Surface, Bed, and Thickness. Corresponding CSV files are included with each GeoTIFF grid. Cell size was defined so 50 percent of cells must contain at least one sample point. Ordinary Kriging interpolation was used to interpolate the data from the flightlines Grid file value -9999 indicates 'NoData'. The provided XYZGrid files, for example 2010_PineIsland_Coarse_XYZGrid.csv, contain the values for Surface, Bed, and Thickness.
Table 4 lists the various grid sizes used during campaigns.
| Campaign | Grid Cell Size |
|---|---|
| Pine Island Glacier Coarse Grid | 3.0 x 3.0 km |
| Pine Island Glacier Dense Grid | 1.5 x 1.5 km |
| Smith Glacier | 3.5 x 3.5 km |
| Thwaites Glacier | 1.5 x 1.5 km |
| 79N Glacier Coarse Grid | 3.5 x 3.5 km |
| 79N Glacier | 2.5 x 2.5 km |
| Petermann Glacier | 2.0 x 2.0 km |
| Petermann Glacier: 1995, 1996, 1997, 1999, 2002, 2003, 2007, 2010, and 2011 Greenland data. | Channel grid: 750 m x 750 m Catchment grid: 1750 m x 1750 m |
Error Sources
The primary error sources for ice penetrating radar data are system electronic noise, multiple reflectors also known as multiples, and off-nadir reflections. Each of these error sources can create spurious reflections in the trace data leading to false echo layers in profile data. Multiple reflectors arise when the radar energy reflects off three surfaces, back-and-forth in the vertical dimension, and then returns to the receive antenna. Reflections occur in situations when multiple surfaces are present with high impedance, such as the upper surface (air/ground), the base of the ice or an ice-water interface, and the aircraft body which is also a strong reflector. The radar receiver only records time since the radar pulse was emitted, so the radar energy that traveled the additional path length appears later in time, apparently deeper in the ice or even below the ice-bedrock interface. Note that multiples of a strong continuous reflector have a similar shape but all slopes appear magnified, that is, doubled in the simplest geometric cases, relative to the main reflection.
Off-nadir reflections can result from crevasse surfaces, water, rock outcrops, or metal structures. Beam structure and processing of the MCoRDS system are designed to reduce these off-nadir reflected energy sources.
Sensor or Instrument Description
As described on the CReSIS Sensors Development Radar Page, the Multichannel Coherent Radar Depth Sounder operates over a 180 to 210 MHz frequency range with multiple receivers developed for airborne sounding and imaging of ice sheets. Measurements are made over two frequency ranges: 189.15 to 198.65 MHz, and 180 to 210 MHz. The radar bandwidth is adjustable from 0 to 30 MHz. Multiple receivers permit digital beamsteering for suppressing cross-track surface clutter that can mask weak ice-bed echoes and strip-map SAR images of the ice-bed interface. These radars are flown on twin engine and long-range aircraft including NASA P-3, DeHavilland Twin Otter (TO), and DC-8. GPS time corrections and frames where no good sync information was available are given in the vector worksheet in the IceBridge MCoRDS L2 Ice Thickness Parameter Spreadsheet.
5. References and Related Publications
Akins, Torry Lee. 1999. Design and development of an improved data acquisition system for the coherent radar depth sounder, Department of Electrical Engineering and Computer Science: Master's Thesis, University of Kansas.
Allen, Christopher, Lei Shi, Richard Hale, Carl Leuschen, John Paden, Benjamin Panzer, Emily Arnold, William Blake, Fernando Rodriguez-Morales, John Ledford, Sarah Seguin. 2011. Antarctic Ice Depth Sounding Radar Instrumentation for the NASA DC-8, submitted for publication to IEEE Transactions on Aerospace and Electronic Systems, August 2011.
Blake, W., J. Ledford, C. Allen, C. Leuschen, S. Gogineni, F. Rodriguez-Morales, Lei Shi. 2008. A VHF Radar for Deployment on a UAV for Basal Imaging of Polar Ice. Geoscience and Remote Sensing Symposium. IGARSS 2008. IEEE International, 4: IV-498-IV-501, doi: 10.1109/IGARSS.2008.4779767.
Byers, K. J. 2011. Integration of a 15-Element, VHF Bow-Tie Antenna Array into an Aerodynamic Fairing on a NASA P-3 Aircraft, Department of Electrical Engineering and Computer Science: Master's Thesis, University of Kansas.
Byers, Kyle J., A. R. Harish, Sarah A. Seguin, Carlton Leuschen, Fernando Rodriguez-Morales, John Paden, Emily Arnold and Richard Hale. 2011. A Modified Wideband Dipole Antenna for an Airborne VHF Ice Penetrating Radar, submitted to IEEE Transactions on Instrumentation and Measurement, June 2011.
Chuah, T. S. 1997. "Design and Development of a Coherent Radar Depth Sounder for Measurement of Greenland Ice Sheet Thickness", CReSIS Technical Report, 151: 175.
Fujita, Shuji, Takeshi Matsuoka, Toshihiro Ishida, Kenichi Matsuoka, and Shinji Mae. 2000. A Summary of the Complex Dielectric Permittivity of Ice in the Megahertz Range and its Application for Radar Sounding of Polar Ice Sheets. Physics of Ice Core Records, (185-212). T. Hondoh, Editor. Hokkaido University Press, 2000, Sapporo.
Gogineni, S., T. Chuah, C. Allen, K. Jezek, and R. K. Moore. 1998. An Improved Coherent Radar Depth Sounder, Journal of Glaciology 44(148): 659-669.
Gogineni, S., D. Tammana, D. Braaten, C. Leuschen, T. Akins, J. Legarsky, P. Kanagaratnam, J. Stiles, C. Allen, and K. Jezek. 2001. Coherent Radar Ice Thickness Measurements Over the Greenland Ice Sheet, Journal of Geophysical Research-Atmospheres 106(D24): 33761-33772.
Lei Shi; C. T. Allen, J.R. Ledford, F. Rodriguez-Morales, W. A. Blake, B. G. Panzer, S. C. Prokopiack, C. J. Leuschen, and S. Gogineni. 2010. Multichannel Coherent Radar Depth Sounder for NASA Operation Ice Bridge, Geoscience and Remote Sensing Symposium (IGARSS), IEEE International, (1729-1732), doi: 10.1109/IGARSS.2010.5649518.
Leuschen, Carl, Chris Allen, Prasad Gogineni, Fernando Rodriguez, John Paden, and Jilu Li. 2011, updated current year. IceBridge Snow Radar L1B Geolocated Radar Echo Strength Profiles, [list dates of data used]. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.
Leuschen, Carl, and Chris Allen. 2010, updated current year. IceBridge MCoRDS L1B Geolocated Radar Echo Strength Profiles, [list dates of data used]. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.
Leuschen, Carl, and Chris Allen. 2011, updated current year. IceBridge MCoRDS L2 Ice Thickness, [list dates of data used]. Boulder, Colorado USA: National Snow and Ice Data Center. Digital media.
Li, Jilu, John Paden, Carl Leuschen, Fernando Rodriguez-Morales, Richard Hale, Emily Arnold, Reid Crowe, Daniel Gomez-Garcia and Prasad Gogineni. 2011. High-Altitude Radar Measurements of Ice Thickness over the Antarctic and Greenland Ice Sheets as a part of Operation Ice Bridge, submitted to IEEE Transactions on Geoscience and Remote Sensing, September 2011.
Namburi, S. P. V. 2003. Design and Development of an Advanced Coherent Radar Depth Sounder, Department of Electrical Engineering and Computer Science, Master's Thesis, University of Kansas.
Paden, John, Christopher Allen, Sivaprasad Gogineni, Kenneth Jezek, Dorthe Dahl-Jensen, and Lars Larsen. 2005. Wideband measurements of ice sheet attenuation and basal scattering, IEEE Geoscience and Remote Sensing Letters, (2)2.
Paden, J. 2006. Synthetic Aperture Radar for Imaging the Basal Conditions of the Polar Ice Sheets, Department of Electrical Engineering and Computer Science, PhD Dissertation, University of Kansas.
Paden, J., T. Akins, D. Dunson, C. Allen, and P. Gogineni. 2010. Ice-sheet bed 3-D tomography, Journal of Glaciology 56(195): 3-11.
Player, K., Lei Shi, Chris Allen, Carl Leuschen, John Ledford, Fernando Rodriguez-Morales, William Blake, Ben Panzer, and Sarah Seguin. 2010. A Multi-Channel Depth-Sounding Radar with an Improved Power Amplifier, High-Frequency Electronics, October 2010: 18-29.
Rodriguez-Morales, F., P. Gogineni, C. Leuschen, C. T. Allen, C. Lewis, A. Patel, L. Shi, W. Blake, B. Panzer, K. Byers, R. Crowe, L. Smith, and C. Gifford. 2010. Development of a Multi-Frequency Airborne Radar Instrumentation Package for Ice Sheet Mapping and Imaging, Proc. 2010 IEEE Int. Microwave Symp., Anaheim, CA, 2010: 157 – 160.
Shi, Lei, C.T. Allen, J.R. Ledford, F. Rodriguez-Morales, W.A. Blake, B.G. Panzer, S.C. Prokopiack, C.J. Leuschen, and S. Gogineni. 2010. Multichannel Coherent Radar Depth Sounder for NASA Operation Ice Bridge, Geoscience and Remote Sensing Symposium (IGARSS), 2010 IEEE International, 25-30 July 2010: 1729-1732.
Related Data Collections
Related Web Sites
6. Document Information
Acronyms and Abbreviations
The acronyms used in this document are listed in Table 5.
| Acronym | Description |
|---|---|
| AGL | Above Ground Level |
| ASCII | American Standard Code for Information Interchange |
| CIRES | Cooperative Institute for Research in Environmental Science |
| CReSIS | Center for Remote Sensing of Ice Sheets |
| CSV | Comma-Separated Values |
| DC-8 | Douglas DC-8 aircraft |
| ESRI | Environmental Systems Research Institute |
| FTP | File Transfer Protocol |
| GPS | Global Positioning System |
| L2 | Processing Level 2 |
| L3 | Processing Level 3 |
| MCoRDS | Multichannel Coherent Radar Depth Sounder |
| PNG | Portable Network Graphics | NASA | National Aeronautics and Space Administration |
| NSF | National Science Foundation |
| NSIDC | National Snow and Ice Data Center |
| P-3 | Lockheed P-3B Orion aircraft | TFW | TIFF World File | TIFF | Tag Image File Format | TO | DeHavilland Twin Otter aircraft |
| TR | Transmit Receive |
| URL | Uniform Resource Locator |
| UTC | Universal Time Coordinated |
| WGS-84 | World Geodetic System 1984 |
Document Creation Date
18 May 2012
Document Revision Date
.....
Document URL
http://nsidc.org/data/docs/daac/icebridge/irmcr3/index.html
