Spanda

Geofencing

Spanda supports WGS84 geofences for safety-critical boundary enforcement, extending the existing local safety { zone ... } model with GPS-native regions.

Declaring a geofence

geofence SafeZone {
  center: geo(30.2672, -97.7431);
  radius: 100.0;
}

The compiler validates latitude/longitude ranges and positive radius during spanda verify.

Safety triggers

on geofence SafeZone exited {
  stop_all_actuators();
  notify_operator();
}

Supported phases: entered, exited (also available as keywords).

Verification

Combine geofences with runtime checks via robot.in_geofence(name):

behavior patrol() {
  if not robot.in_geofence("SafeZone") {
    stop_all_actuators();
  }
}

Triggers fire on boundary transitions:

on geofence SafeZone exited { stop_all_actuators(); }

Note: robot.in_zone() remains for local metric safety zones inside safety { }. Geofences operate in WGS84 coordinates via GPS/GNSS sensors.

Standard library

Types live in std.geofence: GeoFence, GeoPoint.