ALOS PALSAR
Code to read ALOS PALSAR data into ROI_pac has been released. This software works on both FBS (fine beam single-polarization) and FBD (fine beam dual-polarization) raw data (Level 1.0) PALSAR products.
David Sandwell and Rob Mellors have written four programs (ALOS_pre_proc, ALOS_baseline, ALOS_merge, and ALOS_fdb2fbs) for handling raw data format (Level 1.0 products) of ALOS PALSAR. This code is used to preprocess ALOS PALSAR data in L1.0 format. It had been tested with both FBS and FBD mode data at a variety of look angles. Note: the code was written for another processing system and generates an alternate type of ascii parameter files (*.PRM) which differ from the header files that roipac uses (The various *.pl scripts should handle the conversion). The main functions of the code are:
1) ALOS_pre_process - Takes the raw ALOS PALSAR data and aligns the data in the near range. In addition it produces a parameter files in the SIOSAR format containing the essential information needed to focus the data as Single Look Complex (SLC)images.
2) ALOS_baseline - Takes two parameter files of an interferometric pair and calculates the approximate shift parameters needed to align the two images as well as the accurate interferometric baseline at the beginning and end of the frame.
3) ALOS_merge - Appends two raw image files and eliminates duplicate lines. In addition it makes a new PRM file representing the new longer frame.
4) ALOS_fbd2fbs - Converts a raw image file in FBD mode (14 MHz) to an FBS mode (28 MHz) by fourier transformation of each row of the image file (one echo) and padding the spectrum with zeros in the wavenumber domain. A new parameter file is created to reflect the new data spacing and chirp parameters. A complementary ALOS_fbs2fbd program is also available but not automatically compiled with the makefile. The interferograms made from the FBD2FBS conversion have lower noise than the interferograms made from the FBS2FBD conversion.
Their package is available on the ContribSoftware page here at roipac.org and at Rob's site (new version Aug., 2008 now handles quad-pol (PLR) PALSAR): http://www-rohan.sdsu.edu/~rmellors/ALOS_preproc.tar.gz
Note that this software is not part of ROI_pac, so you need to download and compile it separately. The executables should be installed in a directory (e.g., MY_BIN) and the $MY_BIN environment variable set to the location of this directory. The make_raw_alos.pl script in ROI_pac will use $MY_BIN to find the programs.
The Aug. 2008 version now works correctly with polarimetric (PLR) or quad-polarization PALSAR data at Rob's web site: http://www-rohan.sdsu.edu/~rmellors/
An older version of make_raw_alos.pl was included in the ROI_pac version 3.0 release. That script requires the ALOS_pre_process described above as that is not included in the ROI_pac release. The $MY_BIN environment variable must be set to the directory containing the ALOS_pre_process executable to use this script. Note that you should only give the first part of the ALOS IMG filename as the script parameter. The script will search for all files with that start to the name and ending in the -H1.0_A or -H1.0_D suffix.
A new make_raw_alos.pl script has been uploaded here. This version can not only merge a set of ALOS frames, but also perform conversions between FBD and FBS images (Zhenhong Li, 19 Oct 2007). This version can be substituted for the make_raw_alos.pl in ROI_pac version 3.0 with the same requirement that $MY_BIN environment variable must be set to the directory containing the ALOS_pre_process executable (and also the optional ALOS_merge and ALOS_fbd2fbs executables) to use this script. Note: you may need to run dos2unix on this Perl script depending on how your browser downloads it.
For WInSAR members, see the new WInSAR_ALOS_data_orders page for access to PALSAR data.
A pair of PALSAR images over southern California from the WInSAR archive has been processed with ROI_pac using the package describe above. See the ALOS Example page.
processing issues with PALSAR
The ALOS PALSAR system often updates the pulse repetition frequency (PRF) of the SAR acquisitions. This means that many PALSAR pairs have different PRF values for the two scenes. In ROI_pac release 3.0, we have attempted to avoid problems with the initial matching of the two scenes with offset.pl by using a large search distance. This works for scenes where the PRF differs by a small amount (about 0.1 to 0.5% difference), but it may not work for larger differences. We are working on a modification that will work better. (EJF 2007/12/4)
older news
A new script make_raw_alos1.pl was uploaded here Oct. 9. This modified version of make_raw_alos.pl was written to use the two programs ALOS_pre_processor and ALOS_merge to pre-process and merge a set of ALOS frames. It has not been modified yet to work with the version that Rob released this month, so it needs some work but I thought it might help somebody so I post the present state (EJF 2007/10/9). If someone improves this, please post it here or on the ContribSoftware page.
A revised version of make_raw_alos.pl has been uploaded here Sept. 7 that better deals with multiple frames, saving them as separate .raw files for concatenating with ALOS_merge. You might need to rename the files, though (EJF).
A Perl script make_raw_alos.pl calls ALOS_pre_process and reads the .PRM metadata file to produce a .raw.rsc file for processing the preprocessed raw data with ROI_pac. alos2roi_new.tar.gz is a package containing the ALOS_pre_process code and the Perl script originally from Yuri Fialko with modifications by Eric Fielding.
Here is the unmodified package from Yuri Fialko that has a slightly older version of the ALOS_pre_process code and Perl script.