Methodology:

Surveys:

Aerial surveys were carried out using a Mavic Pro from either the MV Pharos or a rigid inflatable boat (RIB), depending on the weather, between the hours of 06:00 and 20:00 local time, from 2023-11-21 to 2023-11-30.

Surveys on the MV SG Pharos were conducted from the helipad and were deployed and retrieved by hand, with one pilot and one observer. Surveys from the RIB were undertaken with a pilot and observer and were deployed and retrieved by hand.

Survey comprised overlapped imagery of target area, with an aim of over 70% overlap and a minimum target altitude at >60m AGL (above ground level). Flights were completed under conditions conducive to UAV specifications. Flights were not pre-programmed. All flights were carried out under South Georgia Regulated Activity Permit number 2023/036.

Stitching:

Images were stitched using Structure-from-Motion (SfM) photogrammetry in Pix4D, where a dense point cloud was extracted and transformed into a DSM (in metres), and then resampled onto a map projection (removing camera perspective and terrain distortions) via orthorectification to create a mosaic. The average ground sampling distance was between 1.94-3.4 cm. Pix4D stitching reports are included in the dataset.

Annotation:

Orthomosaics were annotated for adult albatrosses using QGIS and ArcGIS Pro. All adults were counted, regardless of whether they were on a nest or a non-breeder, using the point tool for vector layers. Birds were distinguished to species level when possible (black-browed albatross: BBA, grey-headed albatross: GHA) and assigned to colony by oblique imagery outlines from previous surveys, which is included in the attribute table.

Data collection:

Instrumentation used: Mavic Pro, Pix4D, QGIS, ArcGIS

Data quality:

Coordinate reference system for ouputs:

Projection: UTM Zone 24S

Horizontal datum: WGS84

Vertical datum: MSL (mean sea level)

For some images, elevation was not retrievable from image metadata and was thus derived from flight logs directly. Flight logs were aligned with images by timestamp to retrieve elevation and then manually inputted into Pix4D for stitching. These are included as additional .csv files. Where colony or flight is null, either the image was not used for stitching or the flight column in the flight log was missing/erroneous and was not used.

For Paryadin South, elevation was not retrievable from the flight logs either, and thus a second subset of the imagery was used, without colonies that were missing elevation values, to derive data without missing values to conduct further analyses.

Some orthomosaics may have some distortion and blurriness, obscuring albatrosses and species-level distinctions in birds.

Some metadata (weather conditions) were not recorded and are thus not included in the UAV flight metadata.