undef
s1a-iw-grd-vv-20170518t205113-20170518t205138-016641-01b9d3-001_filter
s1a-iw-grd-vh-20170518t205113-20170518t205138-016641-01b9d3-002_filter
s1a-iw-grd-vh-20170518t205113-20170518t205138-016641-01b9d3-002_winddir
s1a-iw-grd-vv-20170518t205113-20170518t205138-016641-01b9d3-001_winddir