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Detection process on spatial point process

detection_process.Rd

This function can be used to simulate the detection process when the surveyed individuals are fixed on the geographical space, for example when the species distribution is generated by simul_spat. If strip_transect is emulated, an individual is considered detected if its distance to the track line is lower than the width (provided with sigma). If line-transect is emulated, a half-normal detection function is built using the given sigma as effective strip half-width. The user must define if the simulation is done in a virtual space or not (if not, the distances must be provided in km and pts and transects objects must be projected).

Usage

detection_process(
  pts,
  transects,
  strip_transect = TRUE,
  sigma = NULL,
  seg_id_col = NULL,
  virtual_space = TRUE
)

Arguments

pts

sf object (points), the position of individuals to be surveyed

transects

sf object (lines), survey layout with transects or segments (not buffered)

strip_transect

Boolean. Should strip-transect methodology be used? Default to TRUE

sigma

numeric, is strip_transect is TRUE, the width of the strip width; if strip-transect is FALSE, the effective strip half-width (in km, if in real space)

seg_id_col

character, the name of the column in transects where the ids are stored

virtual_space

Boolean. Is the survey done in a virtual space? Default to TRUE.

Value

the pts dataframe (sf object) with additional columns: distance, distance_km (if in real space), seg_id (the closest transect or segment from the individual) and detected (1 if the individual is detected, 0 otherwise)

See also

simul_spat generate_survey_plan

Other survey simulation functions: assign_flight_plan(), generate_survey_plan(), launch_survey_on_movement()

Examples


grid <- create_grid()
env <- generate_env_layer(grid = grid)
#> [using unconditional Gaussian simulation]
sp <- suppressWarnings(simul_spat(ref_map = env$rasters$sim1,
                 N = 1000, 
                 n_sim = 1, 
                 return_wgs_coordinates = FALSE))

pts <- detection_process(pts = sp, 
                         transects = example_data$survey$segments, 
                         strip_transect = TRUE, 
                         sigma = 0.2, 
                         virtual_space = TRUE,
                         seg_id_col = "seg_id")
#> Strip-transect is used with a width of 0.2
plot(sp$x, sp$y)
plot(sf::st_geometry(example_data$survey$segments), col = "red", add = TRUE)
points(sf::st_drop_geometry(pts[which(pts$detected == 1), c("x", "y")]), 
       pch = 20, col = "blue")