Ice, Cloud, and land Elevation / Geoscience Laser Altimeter System
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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:
The answer is yes! There are several ways to programmatically access NSIDC data products and metadata using Application Programming Interfaces (APIs). We also provide the ability to access data using an FTP client.
"Freeboard" is a measure of the height of sea ice above the ocean surface.
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
There are 40 laser shots in one second which are associated with the transmit pulses from the ICESat/GLAS instrument. The first shot is from the laser, the last shot is the 40th record of that transmitted pulse.
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.
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.
The following steps outline the process for visualizing the GLAS/ICESat 500 m Laser Altimetry Digital Elevation Model of Antarctica (NSIDC-0304) data product in ArcGIS. At the time of writing, these instructions are relevant to ArcMap 10.4
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 instructions below will describe how to extract elevation in text format from GLAS HDF5 Altimetry data using the free open source tool HDFView.
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.
Learn the basic steps for using OpenAltimetry to browse and download ICESat data.
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) 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.