Observed per-fire sizes: one per ignition point, upgraded to mapped area

One size per ignition point. Each point keeps its own SIZE_HA unless a perimeter polygon from the SAME calendar year contains it, in which case the polygon's SIZE_HA replaces it. For NFDB points and NBAC perimeters, this keeps NFDB's full sample (pre-1972 fires, and small fires NBAC does not map) while taking NBAC's satellite-derived area wherever a fire was mapped.

Usage

observed_fire_sizes(
  points,
  polys = NULL,
  min_size_ha = 0,
  ignitions = points,
  ignition_min_ha = 1,
  conflict_m = 500,
  part_gap_m = 250
)

Arguments

points

SpatVector. Ignition points with SIZE_HA and YEAR columns.

polys

SpatVector or NULL. Perimeter polygons with SIZE_HA and YEAR columns. NULL keeps every point's own size.

min_size_ha

Numeric scalar. Sizes below this, and missing sizes, are dropped. Default 0 keeps every positive and zero size.

ignitions

SpatVector. Ignition points with SIZE_HA and YEAR columns, in the CRS of points, tested as other fires in or near a polygon. Every point of ignition_min_ha or more that a same-year polygon contains must be among them, at the same coordinates. Default points.

ignition_min_ha

Numeric scalar, not negative. Smallest ignition (ha) taken to be another fire. Default 1.

conflict_m

Numeric scalar, not negative. Distance (m) within which another ignition disputes a polygon or a group of its parts. Default 500.

part_gap_m

Numeric scalar, not negative. Largest distance (m) between parts of a polygon that are grouped as one fire. Default 250.

Value

Numeric vector of sizes (ha), sorted ascending; at most one element per point.

Details

A polygon can hold more than one fire: NBAC maps some neighbouring fires of the same year as parts of one feature, whose SIZE_HA is the area of them all. A point therefore takes the polygon's SIZE_HA only when no other ignition of that year, of ignition_min_ha or more, lies inside the polygon or within conflict_m of it. Otherwise the polygon's parts are grouped, joining parts no more than part_gap_m apart, and the point takes the area of its own group, measured from the geometry, when no other such ignition lies in or within conflict_m of that group, or keeps its own SIZE_HA when one does. A fire mapped in several parts with no other ignition near it keeps the whole polygon's size. Because the test measures distance to the whole polygon, pass polygons that have not been clipped to a study area, and take ignitions from the whole point record: a fire that burned into a region may have started outside it. The defaults were chosen by comparing candidate rules with agency-mapped fire perimeters. conflict_m and part_gap_m are in metres whatever the CRS's linear unit; a CRS that states no unit is taken to be in metres.

This is the fire-size rule behind save_observed_fire_targets()'s fire_sizes_ha. It is exported so that anything else derived from the same fire record – such as a fitted fire-size distribution – uses the same sizes as the calibration's size target, rather than a second rule that can drift from it. Binding points and polygons as separate rows instead would count every mapped fire twice.

See also

Other Dynamic Fire calibration helpers: apply_calibrated_damage_age(), apply_calibrated_hi_prop(), apply_calibrated_ignprob(), apply_calibrated_num_fires(), bc_fuel_code_to_base(), bc_fuel_label_to_base(), build_calibration_scenario_template(), build_calibration_spinup_scenario(), calibrate_dynamic_fire(), calibration_par_names(), dedup_community_snapshot(), default_severity_prior_sturtevant2009(), fire_cohort_killed(), fire_cohort_mortality(), ground_fire_kill_par_names(), landis_dominant_cohorts(), landis_overstory_mortality_share(), loss_from_stats(), parse_dynamic_fire_logs(), patch_fire_config(), run_calibration_spinup(), run_calibration_validation(), save_observed_fire_targets(), sim_landis(), sim_mock(), sim_r_reimpl()