Satellite tracking, with the CLS:Argos system, has provided enormous benefits to wildlife studies, especially for oceanic bird species. The system provides 2 locations, (1 from each side of the satellite orbit), but they are irregular over time and of variable accuracy. Procedures are described here to identify outlier locations and retain the maximum number of valid observations from DIAG files, thus producing a more homogeneous data set from which to map distributions, track movements, and investigate behaviour, while determining the rate and direction of travel.