NASA Distributed Active Archive Center (DAAC) at NSIDC

ICESat / GLAS Data

Ice, Cloud, and land Elevation / Geoscience Laser Altimeter System

DAAC Home

Example Visualizing Atmospheric Data

1. Windows PC and Macintosh users: To start the Visualizer, navigate to the directory on your computer where you installed the package, double-click the IDL project file "glas_visualizer.prj" and type icesatvis_ds at the IDL prompt.

Unix users: To start the Visualizer, navigate to the directory where you installed the package [your_directory_name]. Then type:

$ cd scf_visualizer/your_directory_name/
$ ./run_visualizer.ksh

You can also run the Visualizer from anywhere, using the following command:

$ /SCF/bin/V2_prelim/run_visualizer.ksh

The following window appears:


2. You have two options at this point:

Select from Data Base: Select all data files in your local directory. Then, specify a specific region and time and/or a set of passes, and the Visualizer will only select files and records within those files that meet your criteria. This allows you to quickly visualize many passes over a small region from multiple data sets at once, and compare them with each other.

Select from Specific Data Set: Select a specific file from your local directory.

The complete functionality of the Select from Data Base option is described on pages 4-13 in "SCF_DVUG_NSIDC.doc." For simplicity, this example will use the Select from Specific Data Set option instead.


3. Click Select from Specific Data Set. The following window appears:

Note the Data Release field with a default value of 19 already filled in. To properly visualize data, you must enter the correct release number. You can find this in the first three digits after "GLAXX" in the file name if you order data from the EOS Data Gateway or Data Pool. For example, "GLA07_019..." indicates Release-19. (Sample files included with the Visualizer do not have the release number in the file names.) Note, however, that the product structures and curves have not yet been updated, and the Visualizer interprets the files as Release-18.

Click Pick next to a data set ID and select a file to view. Refer to the following table for names of each atmosphere data set ID:

Short Name Long Name
GLA02 GLAS/ICESat L1A Global Atmosphere Data
GLA07 GLAS/ICESat L1B Global Backscatter Data
GLA08 GLAS/ICESat L2 Global Planetary Boundary Layer & Elevated Aerosol Layer Heights
GLA09 GLAS/ICESat L2 Global Cloud Heights for Multilayer Clouds
GLA10 GLAS/ICESat L2 Global Aerosol Vertical Structure Data
GLA11 GLAS/ICESat L2 Global Thin Cloud/Aerosol Optical Depths Data

4. If you select a GLA02 or GLA07 file, a Cloud Images window appears with thumbnails of backscatter profiles for each path. These images are created from a decimated selection of the data and only give an idea of what is available. If you select GLA08-11 (without GLA02 or GLA07), profile images are not available; a similar window displays, but the individual thumbnails show only the pass ID.


Example set of cloud profile thumbnails


A Groundtracks window also appears.


Ground track window


5. Left-click on a thumbnail in the Cloud Images window. The corresponding ground track is highlighted, and a GLAS Series Plot Sets window appears. Only plot set buttons that are applicable to products you select are active; other plot sets are disabled.


GLAS Series Plot Sets window


6. Select Attenuated Backscatter Image, 532 nm; then click Launch Selected Plot Sets. You may need to resize the GLAS Series Plot Sets window to see the launch and exit buttons. The GLAS 532nm ATTEN BACKSCATTER window displays a time-series plot of backscatter for the pass. If you also selected GLA08 or GLA09, a variety of cloud, aerosol, and topographic elevations may be superimposed on the image.


Example GLAS attenuated backscatter plot


Start and End give the latitude and longitude of the end points of the displayed section. (Not every plot set has these buttons, but a future release of the Visualizer will enable them for all plot sets.) The default plot title gives the starting date and time (UTC), ending time, and the pass ID. Some plot sets automatically show only the first shot of each second until zoomed in sufficiently to reveal other shot numbers; this is indicated by the "(1Hz)" notation.

Left-click and drag the turquoise vertical lines to set a zoom range, then click Zoom. These cursors are initially at the left and right sides of the plot. A new plot set will appear, showing only the zoomed region.

The Curves button lets you select which curves (currently available in the plot set) to show in the plot. You can also change the color and line properties of individual curves and output data values to the screen.

The Properties button lets you change scales and other plot properties for creating publication-ready plots. The Print button creates a Postscript version of the plot. Both the series and difference windows are plotted. The ThumbnailViewer and ThumbnailZoom "Print..." button option, "Print data rec of 1st tn" has been removed. Instead, try zooming on the thumbnail you want and use the "Print data..." options on the Curve menu for the curve you are intereseted in.

The Save/Res Props... button lets you save the current plot and curve properties (including which curves are plotted) to a file, or restore saved properties from a file. Properties for both the data and difference plots are saved, but the selection of curves differenced are not; this functionality will be added to a future release of the visualizer. You can only restore properties to a plot of the same type. The x-axis range was removed in this version of the Visualizer, because it often caused the plot to appear blank. When saving properties, be sure to specify a directory for which you have write permission; the default is the one from which you launched the visualizer.

Click Close PS File when finished.

Important note: If you try to create either the Postscript or ASCII file in a directory with no write permission, the visualizer may crash. The default is the directory from which the visualizer was run.

Right-clicking on a time-series plot will position a vertical red line. Then click Show on Ground Track to highlight the portion of the pass shown in the plot and to display a diamond-shaped marker at the corresponding location of the red line. Click Display Lidar Profiles to display individual profiles. Left-click an individual profile to display a zoomed window of that profile. Lidar profiles are only available if you selected a GLA02 or GLA07 file. Please consult the ICESat/GLAS Science Computing Facility Visualizion Software User's Guide ("SCF_DVUG_NSIDC.doc"), which is included in the Vizualizer GZIP file , for more information about display options.


Individual backscatter profiles. Annotations: unique record index and shot number; latitude and longitude; solar incidence angle in degrees. The X scale is energy, and the Y scale is altitude in km.