Times when the ROV passed along the underice markers M0 to M10 as obtained from a high definition zoom video camera (Surveyor HD, Teledyne Bowtech, Aberdeen, UK) as obtained on First-Year-Ice (FYI) during the ALERT2018 campaign (Multidisciplinary Arctic Program (MAP) - Last Ice) off Alert, Nunavut, Canada in the Lincoln Sea on 12 and 22 May 2018. Manual post-processing of the position was required because it was distorted probably because sound speed differences were not taken into account during surveys. To correct this distortion, we used the times when the ROV passed along the underice markers M0 to M10 which positions were known from GPS measurements at the surface. The ROV was kept in a stable position at the markers between start and end time. The markers were each separated by 10 m and distributed along a 100 m transect.