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Add simple swept-area estimates to a datras_raw object

Source: R/swept_area.R
add_swept_area_simple.Rd

Compute haul-level swept-area estimates from towing distance and trawl width using a simple rule-based approach.

Usage

add_swept_area_simple(
  x,
  min_speed = 1,
  min_dist = 0,
  max_dist_dev = 0.2,
  impute_missing = FALSE
)

Arguments

x

A datras_raw object.

min_speed

Minimum plausible ground speed. Values below this threshold are treated as missing. Defaults to 1.

min_dist

Minimum plausible towing distance. Values below this threshold are treated as missing. Defaults to 0.

max_dist_dev

Maximum relative deviation allowed between recorded distance and distance reconstructed from HaulDur and GroundSpeed. Distances with larger deviations are treated as missing. Defaults to 0.2.

impute_missing

Logical. Currently included for compatibility, but not used explicitly in the present implementation.

Value

A datras_raw object with two additional swept-area fields:

  • SweptArea: swept area based on haul-specific WingSpread,

  • SweptArea.median: swept area based on gear-specific median wing spread.

Details

The function uses recorded WingSpread where available, applies a series of basic plausibility filters and gear-specific corrections, imputes missing values from gear-level medians, reconstructs towing distance when needed from HaulDur and GroundSpeed, and returns two swept-area estimates.

Swept area is calculated in \(m^2\) as: $$ SweptArea = WingSpread \times Distance $$

A second estimate, SweptArea.median, is also returned. This uses a gear-specific median wing spread rather than the haul-specific recorded or imputed wing spread: $$ SweptArea.median = WingSpread.median \times Distance $$

The function applies the following steps:

  • removes implausible values of GroundSpeed, Distance, and WingSpread,

  • removes distance values that differ too much from reconstructed distance based on speed and haul duration,

  • imputes missing wing spread using gear-specific medians,

  • applies fixed widths for selected beam trawl gear codes,

  • accounts for double-beam trawls via GearEx == "DB",

  • imputes missing ground speed using gear-specific medians,

  • reconstructs missing towing distance from haul duration and ground speed.

See also

add_swept_area_fishglob()

Examples

if (FALSE) { # \dontrun{
x <- add_swept_area_simple(x)

## Use stricter plausibility filtering
x <- add_swept_area_simple(x, min_speed = 2, max_dist_dev = 0.1)
} # }