GLAS/ICESat L2 Ocean Altimetry Data (HDF5), Version 34
Data set id:
GLAH15
DOI: 10.5067/ICESAT/GLAS/DATA212
This is the most recent version of these data.
Version Summary
Version Summary
Release 34 incorporates fixes for several data issues that were determined to exist in the GLAS Release 33 data products.
Overview
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.
Parameter(s):
REFLECTANCESEA SURFACE HEIGHTSEA SURFACE SLOPE
Platform(s):
ICESat
Sensor(s):
ALTIMETERS, CD, GLAS, GPS, GPS Receiver, LA, PC
Data Format(s):
HDF
Temporal Coverage:
20 February 2003 to 11 October 2009
Temporal Resolution:
- 1288 minute
Spatial Resolution:
- 60 m to 70 m
- 60 m to 70 m
Spatial Reference System(s):
ITRF2008
EPSG:5332
Spatial Coverage:
N:
86
S:
-86
E:
180
W:
-180
Blue outlined yellow areas on the map below indicate the spatial coverage for this data set.
Data Access & Tools
A free NASA Earthdata Login account is required to access these data. Learn More
Documentation
User Guide
General Resources
Product Specification Documents
Help Articles
General Questions & FAQs
The ICESat/GLAS 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:
This article covers frequently asked questions about the NASA NSIDC DAAC's Earthdata cloud migration project and what it means to data users.
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.
For ICESat/GLAS mission data, 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.
This short article describes the customization services available for ICESat/GLAS data using Earthdata Search
Surface roughness greatly affects the elevation measurement accuracy. Over most of the ice sheets, the accuracy of each elevation measurement is 15 cm.
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.
Several parameters help quantify the shape of the GLAS laser footprint, which change slightly for each campaign. These parameters are:
How to Articles
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.Users have the option to
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 web interface for discovering and ordering data using spatial and temporal filters. This article explains how to search for ICESat/GLAS data based on spatial and temporal constraints.
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.
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).
The NASA Earthdata Cloud is the NASA cloud-based archive of Earth observations. It is hosted by Amazon Web Services (AWS). Learn how to find and access NSIDC DAAC data directly in the cloud.
All data from the NASA National Snow and Ice Data Center Distributed Active Archive Center (NSIDC DAAC) is directly accessible through our HTTPS file system using Wget or curl. This article provides basic command line instructions for accessing data using this method.
This article highlights the NSIDC DAAC data sets available with customization options and outlines a workflow for searching, ordering, and customizing data in NASA Earthdata Search. This approach is ideal for users who want to download data to their local machine.
HDFView
https://support.hdfgroup.org/products/java/hdfview/
When you first open HDFView, the HDFView window appears with an empty tree and data panel.