This metadata document describes the data contained in the "Argos GPS Processed Data" (Child Item 1) of this data release. This data release contains all data collected by the Argos System from 6 satellite transmitters attached to Glaucous-winged gulls on Middleton Island and 42 Argos-linked GPS satellite transmitters attached to three species of large-bodied gulls (genus Larus) and hybrids thereof, captured at landfills in southcentral, western and northern Alaska. The transmitters carried GPS receivers, so GPS tracking data represent the backbone of this data release. However, because the GPS locations were communicated through the Argos System, a time series of Argos (Doppler) tracking data also exists and is included. Four Comma Separate Value (CSV) tables are included in the "Argos GPS Processed Data" (Child Item 1) of this data release: 1) the "GPS_filteredLocations" table contains one record for every GPS location obtained, accompanied by a binary flag that denotes an algorithm's plausibility check (based on a speed threshold of 35 m/s); 2) the "diag_filteredLocations" table contains one record for every Argos location estimate collected, accompanied by a binary flag that denotes an algorithm's plausibility check (based on distance, turning angle, and rate thresholds). Each record in both the GPS and Argos filtered-location tables also includes a 'Tracking_Status' variable that denotes whether the location was collected from a live animal, a dead animal, or shed transmitter, 3) the "decodedSensor" table contains decoded sensor data such as the transmitter's temperature, battery voltage, and motion (activity), and 4) the "deploymentAttributes" table contains one record for each transmitter deployment in a CSV formatted table. The deployment attributes file contains information such as when the transmitter was attached to the animal, when tracking of a live animal ended, and a variety of variables describing the animal and transmitter. This table is identical to the "deploymentAttributes" table in the "Argos GPS Raw Data" (Child Item 2) of this data release.