Terrestrial laser scanning (TLS) was used to determine the snow surface height above sea level for an approximately 50x50m patch. The reference to sea level was obtained using registration targets drilled through the ice with a measured distance between the target and the water level in the drill holes.

Coordinates:============X and Y coordinates are relative to a GPS base station installed on each floe. Coordinates were determined using post-processing kinematic GPS (PPK-GPS), and corrected for floe ration and drift. Coordinates of measurements inside the laser scanning area were particularly carefully processed to collocate measurements as accurately as possible (within a few cm). The vertical height above sea level in the TLS data was determined by using reflectors on poles. Upon installation of these reflector poles, the ice was drilled through and the height of the reflector above sea level was determined. For details, see Wever et al. (2021).On the floe scale walk, magnaprobe coordinates have been equally processed as in the laser scanning area. However, for the GEM-2 instrument, the position of the magnaprobe was taken for the corresponding time stamp in the GEM-2 data. Since the GEM-2 instrument was following the Magnaprobe surveyor with a few m distance, this leads to less precise positioning. However, the GEM-2 instrument also has a footprint of similar order of magnitude (see Hunkeler et al., 2015).Coordinate reference points:============================All coordinates are relative to GPS base station 1, in a local coordinate system where X and Y coordinates align with easting and northing, respectively, from the respective UTM Zone at a specific point in time. The respective coordinates of GPS base station 1 for this dataset are:For PS81/503: Location of GPS base station 1, July 8 2013, 1646 UTC:WGS84 : latitude=-67.188921 longitude=-13.219895 UTM Zone 28S : northing=2546456 easting=577005