get_detection_area_sum: Calculate the total area sampled by acoustic receivers

In edwardlavender/flapper: Routines for the Analysis of Passive Acoustic Telemetry Data

Calculate the total area sampled by acoustic receivers

Description

This function calculates the total area sampled by receivers, under the assumption of a constant detection range. To implement the function, receiver locations must be supplied as a SpatialPoints or SpatialPointsDataFrame object with the Universe Transverse Mercator coordinate reference system. The get_detection_containers is used to calculate the detection containers around receivers, given a specified detection range (m) and any barriers to detection, such as coastline, and then the total area covered by receivers is calculated, accounting for overlapping containers.

Usage

get_detection_area_sum(
  xy,
  detection_range = 425,
  coastline = NULL,
  scale = 1/(1000^2),
  plot = TRUE,
  ...
)

Arguments

xy, detection_range, coastline, plot, ...	Arguments required to calculate and visualise detection containers via get_detection_containers; namely, receiver locations (xy), the detection range (detection_range), barriers to detection (coastline), and whether or not to plot the containers (plot).
scale	A number that scales the total area (m). The default (1/(1000^2)) converts the units of m^2 to km^2.

Details

This is a simple metric of the overall receiver sampling effort. This may be a poor metric if the assumption of a single detection range across all receivers is substantially incorrect or if there are substantial changes in the receiver array over the course of a study.

Value

The function returns a number that represents the total area surveyed by receivers (by default in km^2) and, if plot = TRUE, a plot of the area with receivers and their detection ranges.

Author(s)

Edward Lavender

See Also

get_detection_containers defines detection containers, across which the detection area is calculated. get_detection_area_ts calculates the area sampled by receivers through time.

Examples

#### Define receiver locations as a SpatialPoints object with a UTM CRS
proj_wgs84 <- sp::CRS(SRS_string = "EPSG:4326")
proj_utm <- sp::CRS(SRS_string = "EPSG:32629")
xy <- sp::SpatialPoints(
  dat_moorings[, c("receiver_long", "receiver_lat")],
  proj_wgs84
)
xy <- sp::spTransform(xy, proj_utm)

#### Example (1): Calculate the total area sampled by receivers
get_detection_area_sum(xy)

#### Example (2): Account for barriers in the study area
get_detection_area_sum(xy, coastline = dat_coast)

#### Example (3): Adjust the detection range
get_detection_area_sum(xy, detection_range = 400, coastline = dat_coast)
get_detection_area_sum(xy, detection_range = 500, coastline = dat_coast)

#### Example (4): Adjust the units
get_detection_area_sum(xy, coastline = dat_coast, scale = 1) # m2

#### Example (5): Suppress the plot
get_detection_area_sum(xy, coastline = dat_coast, plot = FALSE)

edwardlavender/flapper documentation built on Jan. 22, 2025, 2:44 p.m.