prefilter: Prepare Argos data for fitting state-space model

In bmcclintock/crwHMM: Fit Continuous-Time State-Space Models for Filtering Argos Satellite (and Other) Telemetry Data

Description

prefilter (1) determines Argos data type (LS or KF); (2) converts dates to POSIXt & identifies observations with duplicate dates; (3) orders observations in time; (4) removes duplicate observations; (5) removes observations occurring within 60 s of one another (keeps first); (6) shifts longitudes that straddle -180,180 to 0,360 and vice-versa; (7) projects lonlat coords to mercator x,y coords (in km); (8) adds location error multiplication factors based on Argos location class (for type LS); (9) uses a argosfilter::sdafilter to identify potential outlier locations (by distance only) to be ignored when fitting the ctrw model

Usage

prefilter(data, vmax = 50, ang = -1, distlim = c(2500, 5000),
  spdf = TRUE, min.dt = 60)

Arguments

data	input data - must have 5 (LS), or 8 (KF) columns (see details)
vmax	max travel rate (m/s) - see ?argosfilter::sdafilter for details
ang	angles of outlier location "spikes" - see ?argosfilter::sdafilter for details
distlim	lengths of outlier location "spikes" - see ?argosfilter::sdafilter for details
spdf	turn speed filter on/off (logical; default is TRUE)
min.dt	minimum allowable time difference between observations; dt < min.dt will be ignored by the SSM

Details

called by fit_ssm.

Value

an sf object with all observations passed from data and the following appended columns

keep	logical indicating whether observation should be ignored by sfilter (FALSE)
obs.type	flag indicating whether KF or LS measurement model applies
amf_x	Argos error multiplication factor for x direction
amf_y	Argos error multiplication factor for y direction
geometry	sf POINT object giving x,y coordinates in km

Examples

data(ellie)
pf <- prefilter(ellie, vmax=10, ang=c(15,25), min.dt=120)
pf

bmcclintock/crwHMM documentation built on May 7, 2019, 12:51 a.m.