Observable
          .periodic(Duration(seconds: 5))
          .where((_) => _loadState.isNotInProgress())
          .map((_) => _UpdateRaceListRequest(
              (_mapController as dynamic).state.center,
              (_mapController as dynamic).state.zoom,
              DateTime.now()))
          .distinct((prev, next) =>
              prev.zoom - next.zoom < .5 &&
              (prev.center.latitude - next.center.latitude).abs() < .02 &&
              (prev.center.longitude - next.center.longitude).abs() < .01 &&
              next.ts.difference(prev.ts).inMinutes < 1)
          .listen((_) => _updateRaceList()),