===== Orbit Files ===== ROI_PAC is compatible with either ODR or PRC orbits. ==== ODR Orbit Files ==== From the [[http://www.deos.tudelft.nl/ers/precorbs/|Precise Orbit Determination]] web-page, click the "Orbits" link under the content heading. Choose the link for "precise orbits" for the appropriate satellite and follow the download instructions for ODR files **and the arclist**. Remember to also download the program [[http://www.deos.tudelft.nl/ers/precorbs/tools/|getorb]] and install it on your system. :!:The ''getorb'' executable must be located in the ''INT_BIN'' directory with the other ROI_PAC executables. ==== PRC Orbit Files ==== A password is required to download PRC orbits from ESA's website. The file name for PRC orbits can be interpreted as follows: PPP_yymmdd_no_revi.Z |PPP|PRC| |yymmdd|start date of the orbit: year (yy), month (mm), day (dd)| |no|absolute orbit number (revolutions since launch) at orbit begin| |revi|revision id| Retrieve the orbit file with the date and orbit number that most closely __precedes__ the date and orbit of the given SAR scene. After downloading the necessary files, update the list of orbit files by running arclist_PRC.pl in the same directory.