GLAS/ICESat L2 Global Antarctic and Greenland Ice Sheet Altimetry Data (HDF5), Version 34 (GLAH12)
This is the most recent version of these data.
Release 34 incorporates fixes for several data issues that were determined to exist in the GLAS Release 33 data products.
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.
GLACIER ELEVATION/ICE SHEET ELEVATION GLACIER TOPOGRAPHY/ICE SHEET TOPOGRAPHY ICE SHEETS REFLECTANCE
ALTIMETERS, CD, GLAS, GPS, GPS Receiver, LA, PC
20 February 2003 to 11 October 2009
60 m to 70 m
60 m to 70 m
Data Access & Tools
Product Specification Documents
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:
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.
In short, the elevation of the surface at each laser footprint is the height of the spacecraft minus the measured distance to the surface.
Yes, it is an element of GLAH06, GLAH12, GLAH13, GLAH14, and GLAH15.
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.
Surface roughness greatly affects the elevation measurement accuracy. Over most of the ice sheets, the accuracy of each elevation measurement is 15 cm.
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.
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.
Many NSIDC DAAC data sets can be accessed using the NSIDC DAAC's Data Access Tool. This tool provides the ability to search and filter data with spatial and temporal constraints using a map-based interface.
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.
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.
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).
All 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, using wget or curl. Basic command line instructions are provided in the article below.
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.
HDFView https://support.hdfgroup.org/products/java/hdfview/ When you first open HDFView, the HDFView window appears with an empty tree and data panel.