Automatic detection of relevant swaths

[David-Loibl]

In the prepare-data.sh routine, the swath relevant for processing the area of interest should be determined automatically. This will render the manual input in the config file obsolete.
Envisioned work flow:

• Read the orbit direction from S1 annotation XML file:
  grep 'pass' s1a___.xml | tr '<' ' ' | tr '>' ' ' | awk '{print $2}'
• Check if range values are out beyond range range (i.e. < 0, > max) using SAT_llt2rat for each swath
• Add all swaths necessary to process the whole AOI