When a dedicated spotter or signalperson is used to direct pile driving operations, what is required for the signals being used?

1. Signals can be improvised on the spot as long as both parties agree silently
2. Standard Method hand signals (or agreed-upon signals) must be used, understood by both operator and signalperson, before operations begin
3. Only voice signals over radio are permitted
4. The operator should ignore the spotter and rely on mirrors