Longitudes unwrap when individuals cross the date line

[ryanreisinger]

When an individual's track crosses the date line (-180/+180), the fitted output is 'unwrapped' (i.e., has longitudes greater than 180 degrees). Should the interanl function wrap_lon be called in fit_ssm?

library(lubridate)
library(foieGras)
track <- data.frame(id = "bird",
                    date = seq(ymd_hms("2012-01-01 12:00:00"), ymd_hms("2012-01-03 12:00:00"), length.out = 40),
                    lc = "3",
                    lon = c(seq(150, 179, length.out = 20), seq(-179, -150, length.out = 20)),
                    lat = seq(-30, - 60, length.out = 40)
                    )

plot(track$lon, track$lat)

fit.track <- fit_ssm(track, time.step = 3, vmax = 1000)

plot(fit.track$ssm[[1]]$predicted$lon, fit.track$ssm[[1]]$predicted$lat)

[ryanreisinger]

Seems so:

library(lubridate)
library(foieGras)
track <- data.frame(id = "bird",
                    date = seq(ymd_hms("2012-01-01 12:00:00"), ymd_hms("2012-01-03 12:00:00"), length.out = 40),
                    lc = "3",
                    lon = c(seq(150, 179, length.out = 20), seq(-179, -150, length.out = 20)),
                    lat = seq(-30, - 60, length.out = 40)
                    )

plot(track$lon, track$lat)

fit.track <- fit_ssm(track, time.step = 3, vmax = 1000)

plot(fit.track$ssm[[1]]$predicted$lon, fit.track$ssm[[1]]$predicted$lat)

# Wrap longitude back
fit.track$ssm[[1]]$predicted$lon <- wrap_lon(fit.track$ssm[[1]]$predicted$lon)
plot(fit.track$ssm[[1]]$predicted$lon, fit.track$ssm[[1]]$predicted$lat

[ianjonsen]

issue fixed. fit_ssm/prefilter/sfilter now return longitude on original data interval [-180,180] or [0,360] but wraps appropriately for projection to mercator, prior to fitting SSM.