FTP Data Distribution is no longer available for this data set. The NASA NSIDC DAAC now distributes data through HTTPS, which requires users to log in with an Earthdata Login username and password. Data will continue to be available free of charge.

Get Data

DOWNLOADING DATA VIA HTTPS

To learn more about Earthdata Login and to register for an account, please see How to Register with Earthdata Login. Once you have logged in, data can be downloaded via a Web browser, command line, or client. For help with downloading data, please see Options Available for Bulk Downloading Data from HTTPS with Earthdata Login.

HTTPS

IceBridge Portal: Tool to visualize, search, and download IceBridge data.
IceBridge Portal: Tool to visualize, search, and download IceBridge data.
Data Set ID:
IRMCR3

IceBridge MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom, Version 2

This data set contains products from depth sounder measurements over Greenland and Antarctica taken from the Multichannel Coherent Radar Depth Sounder (MCoRDS). The data were collected as part of NASA Operation IceBridge funded campaigns.

Version Summary:

On August 14, 2013, the MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom data were replaced by Version 2:

  • V02 grid size is 500 m x 500 m. V01 coarse (3 x 3 km) and dense (1.5 x 1.5 km) grids are not included in V02.
  • V02 contains separate grid .txt files for Surface, Thickness, and Bottom.
  • V01 1995_2011_Petermann_Composite data are removed.
  • V01 TIF files are removed; MAT files added in V02.
  • ASCII text grid file is changed from CSV in V01 to .txt in V02.
  • V01 crossover_analysis directory is removed; errors directory is added with .mat and errors.txt files.

Geographic Coverage

Parameter(s):
  • Glaciers/Ice Sheets > Glacier Elevation/Ice Sheet Elevation
  • Glaciers/Ice Sheets > Glacier Thickness/Ice Sheet Thickness
  • Glaciers/Ice Sheets > Glacier Topography/Ice Sheet Topography
Spatial Coverage:
  • N: 90, S: 60, E: 180, W: -180

  • N: -53, S: -90, E: 180, W: -180

Spatial Resolution:
  • Varies x Varies
Temporal Coverage:
  • 1 January 2006
Temporal Resolution: Varies
Data Format(s):
  • PNG
  • MATLAB
  • ESRI Shapefile
  • ASCII Text
Platform(s) AIRCRAFT, DC-8, P-3B
Sensor(s): MCoRDS, RADAR ECHO SOUNDERS
Version: V2
Data Contributor(s): Chris Allen
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.

Allen, C. 2013. IceBridge MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom, Version 2. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: http://dx.doi.org/10.5067/YP1PVPR72IHG. [Date Accessed].

Back to Top

Collapse All / Open All

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 Comma-Separated Value ASCII (CSV), Portable Network Graphics (PNG), Matrix Laboratory (MAT), ASCII text, and ESRI shapefile formats. Table 1 describes the data set directories and file contents.

Table 1. Directories and File Content
Directory File Content
/boundaries/ ESRI shape files of study area extent.
/errors/ CSV and MAT files containing crossover analysis results for the data flightpaths.

ASCII text files containing statistics from the crossover analysis results.

PNG preview image of the crossovers plotted over the flight paths.

Crossovers are corrected season by season, not across season. Errors present are across, not within season.
/flightlines/ ESRI shape files of the flight paths, all data points.

Text file of the flight paths, all data points. A_SURF and A_BED are the variables used to interpolate. If NASA ATM data exists for a season, ATM Surface is used. ICESat data is used, if it exists, for IceFree Areas.

Flightlines are clipped to a 10 km buffer of the boundary (Study Area).
/grids/ ESRI ASCII grids of Surface Thickness, Ice Thickness, and Ice Bottom. Note: Bottom is Ice Bottom; this includes floating ice where appliable.
ASCII rasters for Surface, Thickness, and Bed Elevation are provided. 

An XYZ TXT File containing data from all grids is also provided.
/preview_images/ PNG preview images of the surface, ice thickness, ice bottom and flightlines.
 
Background color on
File and Directory Structure
Background color on
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 2:

Example File Names:

Jakobshavn_2006_2012_Composite_StudyArea.shp
Petermann_2010_2012_Composite_Crossovers_Errors.txt
PineIsland_2009_2010_Composite_Flightlines.prj
Smith_2009_2010_Composite_XYZGrid.txt
Thwaites_2009_2010_Composite_Thickness_Preview.png

Location_Years_Description.xxx

Where:

Table 2. File Naming Convention
Variable Description
Location Gridded bed map location: 79N, Byrd, Helheim, Jakobshavn, Kangerdlugssuaq, KogeBugt, NWCoast, Petermann, PineIsland, RecoverySlessor, Smith, Thwaites.
Composite Years Years of data capture. Example: 2010_2012_Composite.
Description File content description. Examples: StudyArea, Crossovers, Errors, Preview, Flightlines, Bottom, Surface, Thickness, XYZGrid.
.xxx

File type.
.csv = Comma Separated Values text file
.png = Portable Network Graphics file
.mat = MATLAB (Matrix Laboratory) file
.shp = ESRI shapefile (includes associated files: dbf, prj, sbn, sbx, shp., shx)
.txt = ASCII text file

Background color on
File Size

CSV text files range from approximately 32 KB to 6.1 MB.

MAT files range from approximately 16 KB to 2.2 MB.

PNG files range from approximately 464 KB to 2.0 MB.

ASCII text files range from approximately 192 KB to 2.3 MB

ESRI .shp files range from approximately 16 KB to 6.3 MB.

ESRI .dbf files range from approximately 16 KB to 15 MB.

Background color on
Volume

The entire data set is approximately 1.3 GB.

Background color on
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.

Background color on
Temporal Coverage

These data were collected as part of Operation IceBridge funded campaigns from 2010 to 2012. Multi-year data collected prior to Operation IceBridge from 2006 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.

Background color on
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 XYZgrid.txt files contain fields described in Table 3.

Table 3. XYZgrid.txt File Parameters, Description, and Units
Parameter Description Units
X Longitude Degrees
Y Latitude Degrees
Thickness Ice Thickness Meters
Surface Ice Surface Height Meters
Bottom Ice Bottom Height Meters

Sample Data Record

Below is an excerpt from Thwaites_2009_2010_Composite_XYZGrid.txt.

The Thwaites_2009_2010_Composite_Thickness_Preview.png image is shown below.

Background color on

Software and Tools

Software and Tools

CSV files may be opened by any text viewing program.
MAT files may be opened using MATLAB, or using an open source tool such as Octave.
PNG files may be opened using any program capable of reading Portable Network Graphics files.
ASCII text files may be opened using any ASCII text reader.
Shapefiles may be opened using ESRI ArcGIS or other similar GIS software.

Background color on

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.

External Data Used:

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.

Background color on
Derivation Techniques and Algorithms

Flightlines

Each flightline is provided in ESRI shapefile format as well as in an ASCII text file containing flight path data points. Flightlines are clipped to the study extent. The fields, A_SURF and A_BOTT, are used to interpolate the surface and bed respectively. The flightlines are in the NSIDC standard projections. See Operation IceBridge Standard Projections for Gridded Data.

For flightline information for the 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.

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.

Processing Steps

The gridding process varies because of differing methods and data sources.

Grids

Grid files contain values for Surface, Bed, and Thickness. 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 processing:

  • Surface is interpolated using Inverse Distance Weighting (IDW) interpolation in ArcGIS.
  • Bottom is interpolated using TopoToRaster interpolation in ArcGIS. Note: any bottom past the grounding line represents ice bottom not ocean bottom.
  • Thickness is calculated using Surface minus Bottom in ArcGIS.

GridNoDataValue: -9999 indicates 'NoData'.

GridCellSize: 500 m x 500 m.

XYZGrid files contain the values for Surface, Bed, and Thickness.

Version History

On August 14, 2013, the MCoRDS L3 Gridded Ice Thickness, Surface, and Bottom data were replaced by Version 2:

  • V02 grid size is 500 m x 500 m. V01 coarse (3 x 3 km) and dense (1.5 x 1.5 km) grids are not included in V02.
  • V02 contains separate grid .txt files for Surface, Thickness, and Bottom.
  • V01 1995_2011_Petermann_Composite data are removed.
  • V01 TIF files are removed; MAT files added in V02.
  • ASCII text grid file is changed from CSV in V01 to .txt in V02.
  • V01 crossover_analysis directory is removed; errors directory is added with .mat and errors.txt files.

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.

Background color on
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.

Background color on

References and Related Publications

Contacts and Acknowledgments

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

Acknowledgments: 

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. We acknowledge the use of data and/or data products from CReSIS generated with support from NSF grant ANT-0424589 and NASA grant NNX10AT68G.

CReSIS faculty, staff, and students designed, developed, operated, and processed data from the radar systems.

Document Information

DOCUMENT CREATION DATE

18 May 2012

DOCUMENT REVISION DATE

14 August 2013

No technical references available for this data set.
No FAQs or How Tos available for this data set.

Access complete Knowledge Base

Questions? Please contact:
NSIDC User Services
Phone: 1 303 492-6199
Email: nsidc@nsidc.org