he data were collected in the form of temporally and spatially indexed photos from planes collected between February 2020 and March 2021 by APEM Ltd.

APEM’s camera system was fitted into a twin-engine P68 Ravenair aircraft. The plane surveyed at a height of 2,000 feet and a ground speed of 120 knots (138 mph). The aerial digital surveys captured images along ten transects spaced in a saw tooth pattern to achieve full coverage across the targeted area east of Scotland. Data collected approximately two-centimetre ground sample distance (GSD) digital still images. The transect swathe was 960 metres, images were collected continuously (abutting digital still imagery) along the ten transects. The image sea surface area covered was 194 km2, representing 1.5% coverage of the wider surface area. Flights were made in sea states less than 4 on the Beaufort scale.

At the spatial modelling stage of the project, animal numbers were modelled considering environmental and biological inputs of potential relevance. Only predictors that can be assigned to all the relevant effort and sightings data were used.