function main() {
  const accuracy=$data.current.locationAccuracy;
  return <CardContent title="当前位置" fulled={true} headerBlurColor="clear"
    trailing={accuracy===null?'—':'±'+Math.round(accuracy)+' m'}>
    <Map width="fill" height="fill" showUserLocation={true}
      followMode={MapFollowMode.userLocation}
      mapStyle={MapStyle.standard} headingPolicy={MapHeadingPolicy.northUp}
      appearance={MapAppearance.automatic}/>
  </CardContent>;
}