view_hdf version 5 README 1.0 Overview view_hdf is a visualization and analysis tool for accessing data stored in Hierarchical Data Format (HDF) and HDF-EOS (EOS extensions to HDF) files. It is developed by the CERES Data Management Team at NASA Langley Research Center and is distributed by the NASA Langley Atmospheric Science Data Center (http://eosweb.larc.nasa.gov). The view_hdf tool can select and subset variables from either Science Data Set (SDS) or vdata structures in an HDF4 file or datasets in an HDF5 file, render both two- and three-dimensional graphics, and plot geolocated data onto various world map projections. Other features include multiple variable plots, difference plots, and simple statistics. Plots can be saved in as files in a number of different formats or they can be sent directly to a printer. Filtered subsets and statistical results can be written to a file in ASCII format for use in other analysis programs. This tool was developed primarily for the CERES project but can have more general use with many other HDF files, although it does not have the ability to read all HDF structure types. Functionality specific to data files from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) instruments is also included. The view_hdf tool is written in Interactive Data Language (IDL) and uses a graphical user interface to manipulate the data. It has been tested with IDL version 6.1 and higher, and it runs under the IDL Virtual Machine (IDL VM) 2.0 Installation 2.1 Unix view_hdf is available as a tar file or a gzipped tar file from the NASA Langley Atmospheric Science Data Center and can be downloaded from the following URL: http://eosweb.larc.nasa.gov/HPDOCS/view_hdf.html If the gzip version is downloaded, uncompress it with the command: >gunzip view_hdf.tar.gz where > represents the Unix command line prompt. Place the tar file in the directory where you want to have the view_hdf software. Then extract the files from the resulting tar file with the command: >tar xvf view_hdf.tar If the tar version is downloaded, use only the above tar command. The tar extraction will write the files in the view_hdf package into the current directory; it does not create a directory. Additional information is available in Section 2.0 (Installation) of the view_hdf User's Guide. 2.2 Windows A zip file package is available for download from the NASA Langley Atmospheric Science Data Center at the URL http://eosweb.larc.nasa.gov/HPDOCS/view_hdf.html Use a zip file extraction tool such as WinZip or pkzip to extract the files into the directory of your choosing. 2.3 IDL Virtual Machine The IDL Virtual Machine is a free runtime version of IDL available from Exelis Visual Information Solutions at http://www.exelisvis.com/Downloads/ProductDownloads.aspx The IDL VM software may be downloaded from this site or ordered from Exelis VIS on CD at no cost. The site provides installation instructions. Unix tar, gzip and PC zip file packages are available for download from the NASA Langley Atmospheric Science Data Center at the URL http://eosweb.larc.nasa.gov/HPDOCS/view_hdf.html Use the instructions in the appropriate Unix or PC section above for unbundling the tar, gzip or zip file on your system. To use the IDL VM application, 1) In Unix: At the Unix command prompt, type idl -vm. Click anywhere on the IDL VM splash screen to continue. A dialog box appears for selecting the IDL save file. Navigate to the directory where you placed the view_hdf_vm.sav file and select that file. Click the OK button and the view_hdf program will start. 2) In Windows: From Windows Explorer, drag the view_hdf_vm.sav file onto the IDL Virtual Machine Desktop icon created when the IDL VM was installed. Click on the splash screen, and the view_hdf program will start. or Click on the IDL Virtual Machine desktop icon or run the IDL Virtual Machine from the Start menu and click on the splash screen to continue. Use the dialog box that appears to navigate to the directory where you placed the view_hdf_vm.sav file, select that file, and click OK to start the view_hdf program. 3.0 Running view_hdf On Unix systems you can invoke IDL at the Unix command line and start view_hdf at the IDL prompt as shown below: >idl IDL> view_hdf On PC systems you will need to start the IDL development environment (idlde) by clicking on the IDL desktop icon, if available, or via Start > Programs > IDL x.y > IDL (where x.y is the IDL version number). The idlde is also available in Unix by typing the command "idlde" at the Unix command prompt. Once the idlde GUI has started, there are two ways to start view_hdf. The first method is to use File > Open from the menu bar at the top of the GUI and navigate to the view_hdf installation directory to select the view_hdf.pro file. Then compile and run that procedure, using either the Compile and Run options under the Run menu item or using the Compile and Run icons in the toolbar. Note that it may take several seconds to open and to compile view_hdf.pro as it is a large program. The second method is to use the IDL command line in the idlde. First use the IDL cd command to make the view_hdf directory the current directory, e.g., IDL> cd,'c:\view_hdf' then run view_hdf by typing IDL> view_hdf where IDL> is the prompt to the left of the command line text box. A sample data file, CER_ES8_TRMM-PFM_AtLaunch_00000.19980101.50rec, is included in the view_hdf package. This file can be opened in view_hdf to test for correct operation on your system. Note that you may need to use the File -> Change Preferences menu option to bring up a window that will let you customize the locations of several directory paths used by view_hdf. Those settings will be saved and used in future invocations of view_hdf. Detailed view_hdf operating instructions are contained in the view_hdf User's Guide, which is included in PDF format in the view_hdf package. Changes to view_hdf in subsequent minor revisions are contained in the release notes for the current version. A PDF version of the release notes is contained in the view_hdf packages and is available from the view_hdf web site. 4.0 Additional Assistance If there are questions about installing or using the view_hdf software, contact the NASA Langley User and Data Services office. User Services may be reached by e-mail: support-asdc@earthdata.nasa.gov Telephone: 757-864-8656 Fax: 757-864-8807 The User Services mailing address is: NASA Langley Atmospheric Science Data Center User and Data Services Mail Stop 157D Hampton, VA 23681-2199 USA Revision dates: Jan 24, 2008 Sep 30, 2008 Aug 03, 2010: changed link for IDL VM Jan 03, 2012: changed link for IDL VM, changed User Services email address