Functions to filter GPS/Argos locations, as well as assessing the sample size for the analysis of animal distributions. The filters remove temporal and spatial duplicates, fixes located at a given height from estimated high tide line, and locations with high error as described in Shimada et al. (2012)
SDLfilter contains a variety of functions to screen GPS and/or Argos locations, and to plot them on a map.
install.packages("SDLfilter")# Or the development version from GitHub:install.packages("devtools")devtools::install_github("TakahiroShimada/SDLfilter")
There are three main filtering functions.
dupfilter removes temporal and spatial duplicates.
ddfilter removes locations with high error.
depthfilter removes fixes located at a given height from estimated high tide line (e.g. locations on land).
Please see the help pages and Shimada et al. (2012, 2016) for more details.
library(SDLfilter)### Fastloc GPS data obtained from a green turtledata(turtle)### Remove temporal and spatial duplicatesturtle.dup <- dupfilter(turtle)### Remove biologically unrealistic fixesturtle.dd <- ddfilter(turtle.dup, vmax=9.9, qi=4, ia=90, maxvlp=2.0)### Plot the locations on a map# unfilteredplotMap(turtle, point.size = 2, line.size = 0.5, axes.lab.size = 0)# filteredplotMap(turtle.dd, point.size = 2, line.size = 0.5, axes.lab.size = 0,bgmap = "satellite", sb.line.col = "white", sb.text.col = "white")
If you use the function ddfilter, please cite
Shimada T, Jones R, Limpus C, Hamann M (2012) Improving data retention and home range estimates by data-driven screening. Mar Ecol Prog Ser 457:171-180 http://dx.doi.org/10.3354/meps09747
If you use the functions dupfilter or depthfilter, please cite
Shimada T, Limpus C, Jones R, Hazel J, Groom R, Hamann M (2016) Sea turtles return home after intentional displacement from coastal foraging areas. Mar Biol 163:1-14 http://dx.doi.org/10.1007/s00227-015-2771-0
1.2.1 (19 February 2019)