There is a large literature of results using ROI_PAC to process ERS-1 and ERS-2 data, but improvements are ongoing. The new release (Version 3.0) includes at least the following two improvements:
A. Dealing with file sizes larger than 2 Gb (2^31 bytes). This problem was originally diagnosed and solved by Eric Fielding in early 2006 and independently discovered and fixed by Matt Pritchard in 2007. The solution is 3 easy modifications, and applies to the following programs: mdx, delay_shift, new_parse, cchz_wave, cpx2mag_phs, rmg2mag_phs, mag_phs2rmg, and mag_phs2cpx
- Changing fseek and ftell to fseeko and ftello
Any variable that exceeds 2 Gb must be defined as class off_t (you may need to include <sys/types.h> at the start of your file to define this class)
- the compilation flags must include: -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64
B. ERS data produced in CEOS format at ASF has a facility code that was not recognized by ROI_PAC v.3.0 (AKCEOS), but this is now included in v.3.0.1. For now you can download tarred scripts (including make_raw_ASF.pl) and instructions (README file) at:http://www.geo.cornell.edu/eas/PeoplePlaces/Faculty/matt/ROI_PAC4ERS_ASF.tar These codes produced results published in Pritchard & Simons, 2004.
ERS orbits
ROI_pac can use three different orbit types for processing ERS-1 and ERS-2 data.
ERS data normally comes with orbit data in the file headers, which can be used to process the data with OrbitType=HDR.
Precise ERS-1 and ERS-2 orbits (called PRC orbits) can be obtained from ESA. Contact the ESA Earth Observation Help Desk [eohelp@esa.int] to get the download information. Select OrbitType=PRC to process with these orbits.
The Delft University of Technology used to calculate precise orbits for ERS-1 and ERS-2 called the ODR orbits. You have to install the "getorb" program from them to use these with ROI_pac http://www.deos.tudelft.nl/ers/precorbs/tools/getorb/. Select OrbitType=ODR to process with these orbits.
ERS File Formats
ERS data has been produced in several different formats. The original ERS CEOS format was originally distributed on tape or CD-ROM. This is now distributed by WInSAR and other organizations as archives compressed with zip or other programs. In recent years, there have been a number of other formats with more info below.
new ESA CEOS format
We have found the cause of our problem with the new ESA data. It is actually not the new CEOS format, but the way files are named on the ESA FTP site. What they deliver as a *.gz file is actually a *.tar.gz file. It took some iterations between us and the HelpDesk to figure that out. Upon a proper unpacking, one ends up with the usual DAT LEA VDF etc. files. The PGS ("new CEOS") format works well with our pre-processors. So the good news is that we don't have to change anything. People who are getting Cat-1 data from ESA may benefit from this info, so feel free to propagate. Yuri
Noel Gourmelen similarly reports receiving files from ESA with naming similar to: ER02_SAR_RAW_0P_20020111T184028_20020111T184044_ESR_035180.CEOS
Which were actually tar files containing CEOS format LEA, DAT, ... files, but didn't have the ".tar" suffix.
GeoEarthScope SuperCEOS format
I think some of the GeoEarthScope data came from ESA in the "new CEOS" format and some came from ASF in STF (Sky Telemetry Format), mostly within the ASF receiving station mask. Only the latter requires use of the SuperCEOS converter to get CEOS format files. The SuperCEOS format data should work with the standard make_raw.pl in ROI_pac except that it might require a small modification to allow a different "facility" name.
new ESA "Envisat-type" format
Since about early 2008 (?), ESA has been offering two product formats for ERS data. One is a CEOS format, with a DAT file and a LEA file (plus a couple others) that is similar to what they have been using for a long time. This is usually delivered in a tar archive (see above). The second format is a single raw data and header file that is similar to the format of Envisat ASAR data. I have not seen one of the "Envisat-type" ERS files, but I understand they have filenames similar to the Envisat names, except that they start with "SAR_IM_0P" and end in ".E2" (for ERS2) instead of ".N1" (for Envisat 1). The ROI_pac releases up to 3.0.1 can only handle the CEOS format. The ESA Envisat-type format document is here.
Marie-Pierre Doin has modified the programs to read the "Envisat-type" format ERS data. There is a new program new_parse_ers.c and Perl script make_raw_ers.pl uploaded here. Note that the Envisat-like format does not include a full set of state vectors, so it is not possible to use the HDR orbit option with this data. You will need to get the ODR or PRC orbits. This new code is "beta" so please let us know if you make further improvements.