Function to filter temporal duplicates that are associated with the same quality index.
dupfilter_time(sdata, step.time = 0)A data frame containing columns with the following headers: "id", "DateTime", "lat", "lon", "qi".
The function filters the input data by the unique "id".
"DateTime" is date & time in class POSIXct.
"lat" and "lon" are the latitude and longitude of each location in decimal degrees.
"qi" is the numerical quality index associated with each location fix where a greater number indicates a higher accuracy
(e.g. the number of GPS satellites involved in estimation).
Consecutive locations less than or equal to step.time apart are considered temporal duplicates. Default is 0 hours.
The input data frame is returned with temporal duplicates removed.
This is a partial component of dupfilter, although works as a stand-alone function.
First it identifies temporal duplicates by searching for consecutive locations that were obtained within step.time.
For each group of temporal duplicates, the function then retains a single fix that is nearest from a previous and to a subsequent location.
Shimada T, Limpus C, Jones R, Hazel J, Groom R, Hamann M (2016) Sea turtles return home after intentional displacement from coastal foraging areas. Marine Biology 163:1-14 doi:10.1007/s00227-015-2771-0
dupfilter, dupfilter_exact, dupfilter_qi, dupfilter_space, track_param