Great Skua flight height data

This file was created with R. 'Bird.id', 'date_time', 'latitude', 'longitude', 'altitude', 'positiondop' and 'speed' were collected by GPS tags. 'Positiondop' is dilution of precision. 'Altitude' is measured in m and 'speed' in km/h. 'Marine' denotes observations over land (0) or sea (1), derived from overlaying the GPS measurements on a map in ArcGIS. Tidal data ('tidal.state' in m) were from the British Oceanographic Data Centre (https://www.bodc.ac.uk/data/online_delivery/ntslf/), using tide gauge from Lerwick and Wick. Surface elevation ('land_height' in m) was obtained from the Shuttle Radar Topography Mission 90 m digital elevation data (http://srtm.csi.cgiar.org/http://srtm.csi.cgiar.org/), aggregated at the 1 km square level. Sunrise and sunset information was obtained using the NOAA Sunrise/Sunset Calculator (http://www.srrb.noaa.gov/highlights/sunrise/sunrise.html).