undef

s1a-iw-grd-vv-20170518t102453-20170518t102522-016635-01b9a2-001_filter

s1a-iw-grd-vh-20170518t102453-20170518t102522-016635-01b9a2-002_filter

s1a-iw-grd-vh-20170518t102453-20170518t102522-016635-01b9a2-002_winddir

s1a-iw-grd-vv-20170518t102453-20170518t102522-016635-01b9a2-001_winddir