Data Set ID:
GLAH12

GLAS/ICESat L2 Global Antarctic and Greenland Ice Sheet Altimetry Data (HDF5), Version 34

GLAH06 is used in conjunction with GLAH05 to create the Level-2 altimetry products. Level-2 altimetry data provide surface elevations for ice sheets (GLAH12), sea ice (GLAH13), land (GLAH14), and oceans (GLAH15). Data also include the laser footprint geolocation and reflectance, as well as geodetic, instrument, and atmospheric corrections for range measurements. The Level-2 elevation products, are regional products archived at 14 orbits per granule, starting and stopping at the same demarcation (± 50° latitude) as GLAH05 and GLAH06. Each regional product is processed with algorithms specific to that surface type. Surface type masks define which data are written to each of the products. If any data within a given record fall within a specific mask, the entire record is written to the product. Masks can overlap: for example, non-land data in the sea ice region may be written to the sea ice and ocean products. This means that an algorithm may write the same data to more than one Level-2 product. In this case, different algorithms calculate the elevations in their respective products. The surface type masks are versioned and archived at NSIDC, so users can tell which data to expect in each product. Each data granule has an associated browse product.

This is the most recent version of these data.

Version Summary:

Release 34 incorporates fixes for several data issues that were determined to exist in the GLAS Release 33 data products.

STANDARD Level of Service

Data: Data integrity and usability verified

Documentation: Key metadata and user guide available

User Support: Assistance with data access and usage; guidance on use of data in tools

See All Level of Service Details

Parameter(s):
  • GLACIERS/ICE SHEETS > GLACIER ELEVATION/ICE SHEET ELEVATION
  • GLACIERS/ICE SHEETS > GLACIER TOPOGRAPHY/ICE SHEET TOPOGRAPHY
  • GLACIERS/ICE SHEETS > ICE SHEETS
  • SEA ICE > REFLECTANCE
Data Format(s):
  • HDF
Spatial Coverage:
N: 86, 
S: -86, 
E: 180, 
W: -180
Platform(s):ICESat
Spatial Resolution:
  • 60 m to 70 m x 60 m to 70 m
Sensor(s):ALTIMETERS, CD, GLAS, GPS, GPS Receiver, LA, PC
Temporal Coverage:
  • 20 February 2003 to 11 October 2009
Version(s):V34
Temporal Resolution1288 minuteMetadata XML:View Metadata Record
Data Contributor(s):David Hancock, H. Zwally, Robert Schutz, John Dimarzio

Geographic Coverage

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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.

Zwally, H. J., R. Schutz, D. Hancock, and J. Dimarzio. 2014. GLAS/ICESat L2 Global Antarctic and Greenland Ice Sheet Altimetry Data (HDF5), Version 34. [Indicate subset used]. Boulder, Colorado USA. NASA National Snow and Ice Data Center Distributed Active Archive Center. doi: https://doi.org/10.5067/ICESAT/GLAS/DATA209. [Date Accessed].

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How To

Programmatic Data Access Guide
Data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) can be accessed directly from our HTTPS file system or through our Application Programming Interface (API). Our API offers you the ability to order data using specific temporal and spatial filters... read more
Stepping through the HDFView User Guide with GLAS HDF5 Data
HDFView https://support.hdfgroup.org/products/java/hdfview/ When you first open HDFView, the HDFView window appears with an empty tree and data panel. The main window consists of six different components: Menu bar, Tool bar, File... read more
How do I order subsetted ICESat/GLAS HDF5 data in Earthdata Search?
NASA Earthdata Search is a map-based search and order tool, allowing you to search for ICESat/GLAS data based on spatial and temporal constraints. Additionally, you can subset files based on spatial bounding box, parameter, and temporal range, as... read more
ICESat, IceBridge, and ICESat-2: A primer on data access across the three missions
This guide will provide an overview of the altimetry measurements and data sets across the missions, as well as a guide for accessing the data through NASA Earthdata Search and programmatically using an Application Programming Interface (API). Overview  The NASA ICESat, Operation IceBridge, and... read more
Search, order, and customize NSIDC DAAC data with NASA Earthdata Search
NASA Earthdata Search is a map-based interface where a user can search for Earth science data, filter results based on spatial and temporal constraints, and order data with customizations including re-formatting, re-projecting, and spatial and parameter subsetting. Thousands of Earth science data... read more
Filter and order from a data set web page
Many NSIDC data set web pages provide the ability to search and filter data with spatial and temporal contstraints using a map-based interface. This article outlines how to order NSIDC DAAC data using advanced searching and filtering.  Step 1: Go to a data set web page This article will use the... read more
How do I convert an HDF5/HDF-EOS5 file into binary format?
To convert HDF5 files into binary format you will need to use the h5dump utility, which is part of the HDF5 distribution available from the HDF Group. How you install HDF5 depends on your operating system. Full instructions for installing and using h5dump on Mac/Unix and... read more

FAQ

Are the altimetry data adjusted to the Geoid, or only to the Ellipsoid?
The elevation data are relative to the ellipsoid. The data also have a parameter indicating the geoid height, which is the height of the EGM2008 geoid above the TOPEX/Poseidon ellipsoid for the first and last shot in the record: GLAH06 Data_40HZ/Geophysical/d_gdHt GLAH12 Data_40HZ/... read more
What is the accuracy of GLAS elevation measurements?
Surface roughness greatly affects the elevation measurement accuracy. Over most of the ice sheets, the accuracy of each elevation measurement is 15 cm. Average ice elevation changes less than 1 cm will be detected by averaging the elevation differences observed at many points in selected regions of... read more
How is the surface elevation at each laser footprint determined?
In short, the elevation of the surface at each laser footprint is the height of the spacecraft minus the measured distance to the surface. A standard parameterization is used to calculate surface elevation for ice sheets, oceans, and sea ice, using the elevation of the maximum peak and no more... read more
In the GLAS altimetry products, is there an indicator to the presence of clouds?
Yes, it is an element of GLAH06, GLAH12, GLAH13, GLAH14, and GLAH15.  The Multiple Scattering Warning Flag, cld1_mswf_flg, is based on the total column optical depth (aerosol plus cloud) calculated in GLAH11 using 532nm. It is intended as a way to quickly obtain information about the potential... read more
What is the basic difference between a standard and alternate waveform fit and when would you normally choose one over the other?
The standard waveform fit is optimized for "ice sheet-like" returns. The majority of these are single-peaked, narrow waveforms. The standard fit allows for only two peaks. Alternate waveform fitting is meant to capture up to six peaks. More peaks are necessary for more complex waveforms over land,... read more
Do you have code for reading HDF data files into MATLAB, IDL, Python, or NCL?
The HDF Group has example code for access and visualization of MODIS, GLAS HDF5, AMSR-E, and NISE data in MATLAB, IDL, Python, and NCL.
How does GLAS geolocate data and provide off-nadir pointing?
Analysis of altimetric data acquired by the GLAS instrument requires accurate determination of the laser spot location on the Earth's surface (ice, land, water, clouds) or geolocation of the laser spot. The spot location with respect to the Earth's center of mass (geocenter) is determined by both... read more
What data subsetting and reformatting services are available for ICESat/GLAS data?
The following table describes the data subsetting and reformatting services that are currently available for ICESat/GLAS HDF5 data via the NASA Earthdata Search tool. Short name Title Subsetting Reformatting... read more