# Aether runtime configuration.
#
#     cp .env.example .env
#
# Read at startup, so changes take effect on restart with no rebuild. Every value here
# is operational configuration: Aether needs no credentials of any kind, and the ADS-B
# feed it polls requires no API key.
#
# Your `.env` is git-ignored and should stay that way. Nothing secret belongs in it
# either — if this project ever grows a credential, it belongs in the environment or a
# secret store, not in a file that lives next to the source.

# Observer position, the origin of the local ENU frame. Default: Athens.
SITE_LAT=37.9838
SITE_LON=23.7275
SITE_ALT_M=70

# Live ADS-B feed. {lat} {lon} {dist} are substituted at runtime.
ADSB_URL=https://api.adsb.lol/v2/lat/{lat}/lon/{lon}/dist/{dist}
ADSB_RADIUS_NM=250

# Hard ceiling on one response body, bytes. Bounds memory against a hostile or broken
# upstream; the parser is never the limit. 8 MiB is ~90x the observed steady-state
# response for this site and radius (measured: 91,547 / 91,543 / 91,543 bytes), so it
# cannot fire on legitimate traffic even at a much larger radius.
MAX_BODY_BYTES=8388608

# Sensor poll period and tracker cycle period, milliseconds.
POLL_MS=2000
CYCLE_MS=1000

# Drop a track after this many seconds with no accepted observation.
TRACK_TIMEOUT_S=45

# Conjunction screening: look-ahead horizon and separation minima.
# 9260 m = 5 NM lateral, 305 m = 1000 ft vertical (ICAO en-route minima).
HORIZON_S=180
MIN_HORIZ_M=9260
MIN_VERT_M=305

# Kalman tuning. Q = process noise PSD (m^2/s^3), R = measurement variance (m^2).
PROCESS_NOISE=4.0
MEAS_VAR=900.0

# Reject a measurement beyond this many sigma of the innovation.
GATE_SIGMA=5.0

# Rows of the air picture to render.
DISPLAY_ROWS=18