Simulation Outputs

Every reporting interval the simulator exposes a PropagatorOutput snapshot via Propagator.get_output(). The CLI persists these snapshots as GeoTIFF rasters, GeoJSON isochrones, and metadata JSON; programmatic users can consume them directly (see the Programmatic Workflow).

All per-cell fields are 2D arrays with the same shape as the input rasters, aggregated across the stochastic realizations of the run.

Fields

Field	Units	Description
time	seconds	Simulation time of the snapshot, from simulation start.
fire_probability	[0, 1]	Fraction of realizations in which the cell has burned.
min_arrival_time	seconds	Earliest time the fire reached the cell across all realizations in which it burned. Cells never reached hold 0.
mean_arrival_time	seconds	Mean arrival time over the realizations in which the cell burned.
ros_mean	m/min	Mean rate of spread over realizations where the cell burned.
ros_max	m/min	Maximum rate of spread across realizations.
fli_mean	kW/m	Mean fireline intensity over realizations where the cell burned.
fli_max	kW/m	Maximum fireline intensity across realizations.
spotting_generation_probability	[0, 1]	Fraction of realizations in which the cell launched at least one ember (all zeros when spotting is disabled). See Fire Spotting.
spotting_receiving_probability	[0, 1]	Fraction of realizations in which the cell was hit by an ember (all zeros when spotting is disabled).
stats	—	Aggregate statistics: number of active cells and burned-area mean and 50/75/90th percentiles.

Arrival Times

Arrival times record, per realization, the simulation time at which each cell ignited. They are useful to derive isochrone maps from a single realization ensemble, or to quantify the spread of arrival uncertainty:

output = sim.get_output()

# Earliest possible arrival (best-case warning time)
earliest = output.min_arrival_time

# Expected arrival where the fire is likely to reach
expected = output.mean_arrival_time

Both arrays are expressed in seconds from simulation start. min_arrival_time is the minimum over the realizations in which the cell burned, so cells with a low fire_probability can still carry a meaningful (if unlikely) early arrival time — combine it with fire_probability when communicating risk.

CLI Raster Products

When running through the CLI, each reporting interval writes one GeoTIFF per variable: fire_probability, min_arrival_time, mean_arrival_time, ros_mean, ros_max, fireline_intensity_mean, fireline_intensity_max, and — when spotting is enabled in the configuration — spotting_generation_probability and spotting_receiving_probability. See CLI Usage for invocation details.