How does a geofence differ from a warrant to search a property? While crimes are known to have occurred, the exact people may not be known. The biggest differe

How does a geofence differ from a warrant to search a property? While crimes are known to have occurred, the exact people may not be known. The biggest difference I see "time". Mostly that it can be done retroactively. Would a geofence be allowed while the event is occurring?