General Information ------------------- This is the NSIDC GLAS Altimetry elevation extractor Tool (NGAT) version 0.12 This software is designed to allow users to extract elevation and geoid data from GLAS altimetry products (GLA06,12,13,14,15). Works on Release 12 through Release 31 data. The NGAT is a freely distributed tool and is provided as is without any warranties implied or stated. Copyright (C) 2006 University of Colorado. Portions of the code distributed under the following license. ;- ; Copyright (C) 1997-2003, Craig Markwardt ; This software is provided as is without any warranty whatsoever. ; Permission to use, copy, modify, and distribute modified or ; unmodified copies is granted, provided this copyright and disclaimer ; are included unchanged. ;- Contact Information: User Services National Snow and Ice Data Center CIRES, 449 UCB University of Colorado Boulder, CO 80309-0449 Phone: +1 (303) 492-6199 Fax: +1 (303) 492-2468 E-mail: email@example.com About the tool -------------- The NGAT lets a user extract information from an ICESat/GLAS binary altimetry file. The information is presented in an easy to use column output format. The output data look like this. 372403915 03/07/2004 00:33:11.540 69.711446 209.602310 134.482 -0.220000 372403915 03/07/2004 00:33:11.565 69.712961 209.601311 135.949 -0.225128 372403915 03/07/2004 00:33:11.590 69.714476 209.600318 138.315 -0.230256 372403915 03/07/2004 00:33:11.615 69.715991 209.599331 140.208 -0.235385 Columns are: Record Number - 1 record (40 samples) Date - MM/DD/YYYY Time - HH:MM:SS.sss Latitude - 'i_lat' converted to degrees Longitude - 'i_lon' converted to degrees elevation - the 'i_elev' field for the chosen product number, converted to meters geoid - the 'i_gdHt' values, interpolated for each shot also converted to meters Please see the GLAS Altimetry Data Dictionary (http://nsidc.org/data/docs/daac/glas_altimetry/data_dictionary.html) for descriptions of 'i_lat', 'i_lon, 'i_elev', and 'i_gdHt' Starting with Version 0.9, i_satRngCorr / i_satElevCorr and i_gval_rcv can be appended to the list of output variables by setting show_saturation_gain_corrections to a non-zero value in the batch_read_altimetry.ini file. Again, please see the GLAS Altimetry Data Dictionary for further information about these variables. Starting with Version 0.11, i_satRngCorr / i_satElevCorr, i_gval_rcv, and i_UTCTime in decimal seconds to 3 decimal places (i.e. having 1 millisecond precision) can all be appended to the list of output variables by setting show_saturation_gain_corrections to a non-zero value in the batch_read_altimetry.ini file. Again, please see the GLAS Altimetry Data Dictionary for further information about these variables. Prerequisites ------------- The NGAT runs under IDL (6.2 or greater) or the free IDLVM. Please see RSI's website for information on how to install the free IDL virtual machine. www.rsinc.com/idlvm Installation ------------ No installation is required for the tool. Instructions ------------ The user needs to set up a batch_read_altimetry.ini file. This contains the input parameters for processing, such as, input/output directories, input/output file names, product number, release number, starting record and number of records to process. Unix: At the command line, in the directory containing the batch_read_altimetry.sav file as well as the batch_read_altimetry.ini file type, prompt> idl -vm="batch_read_altimetry.sav" Windows: make sure the batch_read_altimetry.ini is in the same directory as the batch_read_altimetry.sav and just double click the batch_read_altimetry.sav file. A confirmation dialog should pop up to let you know processing has finished. Manifest -------- Your kit should contain the following files: 00README.txt - this file batch_read_altimetry.sav - the binary code for the tool batch_read_altimetry.ini - the sample file that configures the input/output and product options ReleaseNotes.txt - Inventory of product history.