Hyperion Tools 2.0 Installation and User Guide

Author:

Devin White, PhD (Devin.White@gmail.com)

Introduction

The Hyperion Tools plugin is designed to facilitate the use of Hyperion data in ENVI.  Its most basic functionality is to covert Level 1R HDF and Level 1G/1T HDF and GeoTIFF datasets into ENVI format files that contain wavelength, full width half maximum, and bad band information. Also included are options specific to each input dataset format that further aid in u sing Hyperion data within ENVI.

Version 2.0 includes a complete overhaul of the underlying codebase, resulting in significantly faster conversion times, several new file output options, support for the new L1R format (L1R + AUX), and an application programming interface (API) that enables batch processing.  The API is presented after brief discussions on the installation and use of the plugin.

Download hyperion_tools.zip

Installation

To  add  the  toolkit  to  your  ENVI  installation,  place  the  hyperion_tools.sav, flag_mask_settings.txt, and hyperion_wl_fwhm_bbl.txt files in your ENVI save_add and/or extensions folder.  The location of this folder will vary by operating system and ENVI version.

ENVI 4.3:        Windows: c:\rsi\idl63\products\envi43\save_add

UNIX\Linux: /usr/local/rsi/idl_6.3/products/envi_4.3/save_add

Mac:  /applications/rsi/idl_6.3/products/envi_4.3/save_add

ENVI 4.4-4.8: Windows: c:\program files\itt\idlXX\products\enviXX\save_add UNIX\Linux: /usr/local/itt/idl_X.X/products/envi_X.X/save_add Mac:  /applications/itt/idl_X.X/products/envi_X.X/save_add

ENVI 5.0+ Standard:  Windows: c:\program files\exelis\enviXX\extensions UNIX\Linux: /usr/local/exelis/enviXX/extensions Mac:  /applications/exelis/enviXX/extensions

ENVI 5.0+ Classic:     Windows: c:\program files\exelis\enviXX\classic\save_add UNIX\Linux: /usr/local/exelis/enviXX /classic/save_add Mac:  /applications/exelis/enviXX /classic /save_add

NOTE:  To use Hyperion Tools in ENVI 5.0+, you must perform both the Standard and Classic mode installations.

To access the tools after installation, go to File->Open External File->EO-1->Hyperion Tools in

ENVI Classic or double-click on the “hyperion_tools” button in the Extensions folder in ENVI

5.0+.

L1R Processing

For L1R data, click on “Input HDF” and select your L1R file.  Then click on “Output Path” and select a destination folder for the new ENVI format version of the data.  Click “Apply” to start the conversion process.  In this mode, the conversion tool will place raw radiance data in the new ENVI file in BIL format and will include averaged wavelength and FWHM values.  The new file shares the same rootname as the input HDF, but the extension is “.dat”.

L1R Options:

·     Attempt Georeferencing:  If there is a metadata (.MET) file packaged with the L1R HDF

that resides in the same folder as the HDF file, and it shares the same rootname as the

HDF, the toolkit will parse the geographic coordinates for the four corners and include them in the new ENVI format file.  The projection is only pseudo-geographic.  Also, not all metadata files contain coordinates for the four corners, so the georeferencing might not work.

·    Use Flag Mask Correction:  A small number of Hyperion’s detectors are malfunctioning, which often results in vertical striping in the image that can vary from one band to the next.  Invoking this option gives you an image where the striping has been removed by replacing the bad values with ones linearly interpolated from the remaining good values on the same scan line.  The correction is done on the fly as the original data is retrieved from the HDF and is placed in the new ENVI format file.   The plugin uses the “flag_mask_settings.txt” file to guide the correction process.   This file  contains pre- launch detector health information on a per-pixel, per-band basis (256 x 242); it is also present in every L1R HDF file.   You can modify the file to reflect post-launch health changes (0 = good, 1 = bad).

·    Output ENVI Mask Image:   This option instructs the toolkit to create an ENVI mask image (1 = good data, 0 = bad data) for the data set that suppresses the data acquired by the malfunctioning detectors.  This especially helps when carrying out PCA rotations, Fourier Transforms, and Hourglass Processing with raw data that has not been flag- corrected.  The mask image has the same basic rootname as the converted data file, but has “_mask.dat” appended to it.

·    Output Wavelength/FWHM Tables:   Comma-delimited text files (CSV) are generated that include wavelength and full-width half maximum values for every band of every detector.   These data are pulled directory from the supplied L1R file.   The tables are organized so that bands (242) are the columns and detectors (256) are the rows.  Bands increase from left to right and detectors increase from top to bottom.

·    Output FLAASH Scale Factors:   A small text file is generated in the specified output folder  that  contains  scale  factors  necessary  to  correctly  input  Hyperion  data  into FLAASH. These scale factors are static (not derived from the inputted L1R file).

·    Interpolate Data to Common Wavelength Set:   Each detector in Hyperion’s pushbroom array has slightly different band center and FWHM values for each band.  This option performs a linear or quadratic interpolation across all detectors on a pixel by pixel, spectrum by spectrum, basis to a common set of wavelengths.  The Bad Bands List is honored in this process as well to ensure the best possible results.  The interpolation occurs  on-the-fly  during data  conversion.    The converted  file  includes  wavelengths representing the  new  common set of  band  centers. Averaged  values are  used  for FWHM.  Linear interpolation is used unless the Quadratic button is toggled to “Yes”.

·    Use Quadratic Method:  Toggle this button to “Yes” to use quadratic interpolation.  The button becomes active when the user checks the Interpolate Data to Common Wavelength Set box.

L1G/T Processing

For L1G/1T data, click on “Input MTL” and select the “.L1G” or “.LIT” metadata file that is packaged with the HDF or GeoTIFF files.  Then click on “Output Path” and select a destination folder for the new ENVI format version of the data.   Click “Apply” to start the conversion

process.  In this mode, the conversion tool will place the radiance data in the new ENVI file in BIL format and will include averaged wavelength and FWHM values.  The new file shares the same rootname as the input files, but the extension is “.dat”.  All 242 files must be in the same folder as the MTL metadata file for the conversion to take place.

L1G/T Options:

·    Output ENVI Mask Image:   This option instructs the toolkit to create an ENVI mask image  (1=good  data,  0=bad  data)  for  the  data  set  that  suppresses  the  “black” background present in the georeferenced imagery.   This is useful for almost all ENVI

processing since the background values are not part of the original dataset.  The mask

image has the same basic rootname as the converted data file, but has “_mask.dat”

appended to it.

·    Output FLAASH Scale Factors:   A small text file is generated in the specified output folder  that  contains  scale  factors  necessary  to  correctly  input  Hyperion  data  into FLAASH. These scale factors are static (not derived from the inputted L1G/T file).

·    Output Interleave:  The interleave of the outputted cube can be set to Band Sequential (BSQ), Band Interleaved By Line (BIL), or Band Interleaved By Pixel (BIP).  BIL is the default option.

Using Hyperion Tools Output in FLAASH

To use toolkit output in FLAASH, go into the header file for the output and remove the f irst seven bands from the Bad Bands List. When FLAASH is done, go into the header file for the new output and put the seven bands back on the list.