This was the survey vessel which, in 1958 (and 1960), came to the Sound of Harris to update the chart that had been made 100 years earlier.
The 1959 chart was published as a Revised edition of its 1859 predecessor, which surely is testament to the extraordinary skills of Captain H. C. Otter .
and the crews of 19thC survey vessels, including Captain FWL (Fred) Thomas.
HMS Shackleton was originally commissioned as HMS Sharpshooter but was renamed in 1953 in line with her new duties engaged in hydrographic surveying. She marked five datum points in Leverburgh, Harris and Bays Loch, Berneray using three cuts, a rivet (in Leverburgh) and a bolt (in Berneray).
A very full account of her history can be read here: HMS Shackleton.